Lost top end power in 88 Cherokee 4.0.
Guest
Posts: n/a
Re: Lost top end power in 88 Cherokee 4.0.- Update
Still no joy.
Have a fast idle (2000 rpm) issue when first started that mellows down.
It seems to be an RPM limiter under load.
If floored in neutral, the engine will die, it will not catch back as
the rpm comes down unless the pedal is let up on.
If coaxed up in neutral the engine will rev high.
When in 1st, it picks up fast to about 2000 rpm, then hits a wall.
Holding it to the floor causes 'misses' and sputtering with a decrease
in power and speed until the pedal is let up on.
I have no way to verify fuel pressure other than to say this power issue
has been going on for several weeks with a 'stable' screw up. When
pumps go, they usually go sooner than later totally, but....
Things done:
Cap and rotor
Gas filter
Air filter new
Ran with open gas cap
Checked plugs, all 'very' even and evenly burned almost to the 'worn
out' point with a perfectly 'normal' coloring. Gap was almost 50, put
it back to 35.
That would go with the plug wires also checking out ok on my meter with
an ohm check. They are OEM 'lifetime' wires about 10 years old.
Checked and cleaned CPS (about 5 years old) with attention to the wire's
routing.
Cleaned main battery terminals and cable ends.
Cleaned TPS and checked it for smooth ohm reading all the way up.
Cleaned IAC connection, but not the unit itself??? Can that affect top end?
Cleaned coil connections and verified the meter readings. Seem ok. Got
1.5 ohm between the plus and minus pins, infinity between plus and case
and 'less than infinate' my books says between coil negative and high
tension post or 4.5 K ohm on the meter.
Unplugged EGR. No change so put it back.
Cleaned connections on the MAP sensor and verified the vacuum line.
I have to wait until later to have a friend go under to blow out the
fuel pump.
Mike
Mike Romain wrote:
> Ok, I am on a fishing expedition for likely things to check.
>
> Our 88 Cherokee with the 4.0 has lost power above half throttle. It
> goes fine up to that point, then just bogs, no matter what gear it is
> in. It has been neglected for 4 years as far as tuning goes due to me
> not being up to it.
>
> I first changed out the 'very' dirty distributor cap and rotor which
> made starting 'much' faster and smoother.
>
> I then changed the gas filter because it was once again rusted to the
> rot point after about 8 years.
>
> Air filter is new.
>
> I cleaned the connections on the TPS and IAC and verified the TPS
> doesn't have any 'dead' spots with my meter.
>
> I cleaned the CPS and coil connections also.
>
> No joy on any of that.
>
> I have been having some cold idle issues and have been thinking on
> cleaning the IAC, but don't know if that will have a top end effect or not.
>
> I am also thinking on unplugging the EGR just to make sure it isn't
> blown vacuum wise because it only bogs under throttle when things like
> the EGR are active.
>
> Any other ideas?
>
> Mike
> 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
> 88 Cherokee 235 BFG AT's
> Canadian Off Road Trips Photos: Non members can still view!
> Jan/06 http://www.imagestation.com/album/pi...?id=2115147590
> (More Off Road album links at bottom of the view page)
Have a fast idle (2000 rpm) issue when first started that mellows down.
It seems to be an RPM limiter under load.
If floored in neutral, the engine will die, it will not catch back as
the rpm comes down unless the pedal is let up on.
If coaxed up in neutral the engine will rev high.
When in 1st, it picks up fast to about 2000 rpm, then hits a wall.
Holding it to the floor causes 'misses' and sputtering with a decrease
in power and speed until the pedal is let up on.
I have no way to verify fuel pressure other than to say this power issue
has been going on for several weeks with a 'stable' screw up. When
pumps go, they usually go sooner than later totally, but....
Things done:
Cap and rotor
Gas filter
Air filter new
Ran with open gas cap
Checked plugs, all 'very' even and evenly burned almost to the 'worn
out' point with a perfectly 'normal' coloring. Gap was almost 50, put
it back to 35.
That would go with the plug wires also checking out ok on my meter with
an ohm check. They are OEM 'lifetime' wires about 10 years old.
Checked and cleaned CPS (about 5 years old) with attention to the wire's
routing.
Cleaned main battery terminals and cable ends.
Cleaned TPS and checked it for smooth ohm reading all the way up.
Cleaned IAC connection, but not the unit itself??? Can that affect top end?
Cleaned coil connections and verified the meter readings. Seem ok. Got
1.5 ohm between the plus and minus pins, infinity between plus and case
and 'less than infinate' my books says between coil negative and high
tension post or 4.5 K ohm on the meter.
Unplugged EGR. No change so put it back.
Cleaned connections on the MAP sensor and verified the vacuum line.
I have to wait until later to have a friend go under to blow out the
fuel pump.
Mike
Mike Romain wrote:
> Ok, I am on a fishing expedition for likely things to check.
>
> Our 88 Cherokee with the 4.0 has lost power above half throttle. It
> goes fine up to that point, then just bogs, no matter what gear it is
> in. It has been neglected for 4 years as far as tuning goes due to me
> not being up to it.
>
> I first changed out the 'very' dirty distributor cap and rotor which
> made starting 'much' faster and smoother.
>
> I then changed the gas filter because it was once again rusted to the
> rot point after about 8 years.
>
> Air filter is new.
>
> I cleaned the connections on the TPS and IAC and verified the TPS
> doesn't have any 'dead' spots with my meter.
>
> I cleaned the CPS and coil connections also.
>
> No joy on any of that.
>
> I have been having some cold idle issues and have been thinking on
> cleaning the IAC, but don't know if that will have a top end effect or not.
>
> I am also thinking on unplugging the EGR just to make sure it isn't
> blown vacuum wise because it only bogs under throttle when things like
> the EGR are active.
>
> Any other ideas?
>
> Mike
> 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
> 88 Cherokee 235 BFG AT's
> Canadian Off Road Trips Photos: Non members can still view!
> Jan/06 http://www.imagestation.com/album/pi...?id=2115147590
> (More Off Road album links at bottom of the view page)
Guest
Posts: n/a
Re: Lost top end power in 88 Cherokee 4.0.- Update
Still no joy.
Have a fast idle (2000 rpm) issue when first started that mellows down.
It seems to be an RPM limiter under load.
If floored in neutral, the engine will die, it will not catch back as
the rpm comes down unless the pedal is let up on.
If coaxed up in neutral the engine will rev high.
When in 1st, it picks up fast to about 2000 rpm, then hits a wall.
Holding it to the floor causes 'misses' and sputtering with a decrease
in power and speed until the pedal is let up on.
I have no way to verify fuel pressure other than to say this power issue
has been going on for several weeks with a 'stable' screw up. When
pumps go, they usually go sooner than later totally, but....
Things done:
Cap and rotor
Gas filter
Air filter new
Ran with open gas cap
Checked plugs, all 'very' even and evenly burned almost to the 'worn
out' point with a perfectly 'normal' coloring. Gap was almost 50, put
it back to 35.
That would go with the plug wires also checking out ok on my meter with
an ohm check. They are OEM 'lifetime' wires about 10 years old.
Checked and cleaned CPS (about 5 years old) with attention to the wire's
routing.
Cleaned main battery terminals and cable ends.
Cleaned TPS and checked it for smooth ohm reading all the way up.
Cleaned IAC connection, but not the unit itself??? Can that affect top end?
Cleaned coil connections and verified the meter readings. Seem ok. Got
1.5 ohm between the plus and minus pins, infinity between plus and case
and 'less than infinate' my books says between coil negative and high
tension post or 4.5 K ohm on the meter.
Unplugged EGR. No change so put it back.
Cleaned connections on the MAP sensor and verified the vacuum line.
I have to wait until later to have a friend go under to blow out the
fuel pump.
Mike
Mike Romain wrote:
> Ok, I am on a fishing expedition for likely things to check.
>
> Our 88 Cherokee with the 4.0 has lost power above half throttle. It
> goes fine up to that point, then just bogs, no matter what gear it is
> in. It has been neglected for 4 years as far as tuning goes due to me
> not being up to it.
>
> I first changed out the 'very' dirty distributor cap and rotor which
> made starting 'much' faster and smoother.
>
> I then changed the gas filter because it was once again rusted to the
> rot point after about 8 years.
>
> Air filter is new.
>
> I cleaned the connections on the TPS and IAC and verified the TPS
> doesn't have any 'dead' spots with my meter.
>
> I cleaned the CPS and coil connections also.
>
> No joy on any of that.
>
> I have been having some cold idle issues and have been thinking on
> cleaning the IAC, but don't know if that will have a top end effect or not.
>
> I am also thinking on unplugging the EGR just to make sure it isn't
> blown vacuum wise because it only bogs under throttle when things like
> the EGR are active.
>
> Any other ideas?
>
> Mike
> 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
> 88 Cherokee 235 BFG AT's
> Canadian Off Road Trips Photos: Non members can still view!
> Jan/06 http://www.imagestation.com/album/pi...?id=2115147590
> (More Off Road album links at bottom of the view page)
Have a fast idle (2000 rpm) issue when first started that mellows down.
It seems to be an RPM limiter under load.
If floored in neutral, the engine will die, it will not catch back as
the rpm comes down unless the pedal is let up on.
If coaxed up in neutral the engine will rev high.
When in 1st, it picks up fast to about 2000 rpm, then hits a wall.
Holding it to the floor causes 'misses' and sputtering with a decrease
in power and speed until the pedal is let up on.
I have no way to verify fuel pressure other than to say this power issue
has been going on for several weeks with a 'stable' screw up. When
pumps go, they usually go sooner than later totally, but....
Things done:
Cap and rotor
Gas filter
Air filter new
Ran with open gas cap
Checked plugs, all 'very' even and evenly burned almost to the 'worn
out' point with a perfectly 'normal' coloring. Gap was almost 50, put
it back to 35.
That would go with the plug wires also checking out ok on my meter with
an ohm check. They are OEM 'lifetime' wires about 10 years old.
Checked and cleaned CPS (about 5 years old) with attention to the wire's
routing.
Cleaned main battery terminals and cable ends.
Cleaned TPS and checked it for smooth ohm reading all the way up.
Cleaned IAC connection, but not the unit itself??? Can that affect top end?
Cleaned coil connections and verified the meter readings. Seem ok. Got
1.5 ohm between the plus and minus pins, infinity between plus and case
and 'less than infinate' my books says between coil negative and high
tension post or 4.5 K ohm on the meter.
Unplugged EGR. No change so put it back.
Cleaned connections on the MAP sensor and verified the vacuum line.
I have to wait until later to have a friend go under to blow out the
fuel pump.
Mike
Mike Romain wrote:
> Ok, I am on a fishing expedition for likely things to check.
>
> Our 88 Cherokee with the 4.0 has lost power above half throttle. It
> goes fine up to that point, then just bogs, no matter what gear it is
> in. It has been neglected for 4 years as far as tuning goes due to me
> not being up to it.
>
> I first changed out the 'very' dirty distributor cap and rotor which
> made starting 'much' faster and smoother.
>
> I then changed the gas filter because it was once again rusted to the
> rot point after about 8 years.
>
> Air filter is new.
>
> I cleaned the connections on the TPS and IAC and verified the TPS
> doesn't have any 'dead' spots with my meter.
>
> I cleaned the CPS and coil connections also.
>
> No joy on any of that.
>
> I have been having some cold idle issues and have been thinking on
> cleaning the IAC, but don't know if that will have a top end effect or not.
>
> I am also thinking on unplugging the EGR just to make sure it isn't
> blown vacuum wise because it only bogs under throttle when things like
> the EGR are active.
>
> Any other ideas?
>
> Mike
> 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
> 88 Cherokee 235 BFG AT's
> Canadian Off Road Trips Photos: Non members can still view!
> Jan/06 http://www.imagestation.com/album/pi...?id=2115147590
> (More Off Road album links at bottom of the view page)
Guest
Posts: n/a
Re: Lost top end power in 88 Cherokee 4.0.- Update
Still no joy.
Have a fast idle (2000 rpm) issue when first started that mellows down.
It seems to be an RPM limiter under load.
If floored in neutral, the engine will die, it will not catch back as
the rpm comes down unless the pedal is let up on.
If coaxed up in neutral the engine will rev high.
When in 1st, it picks up fast to about 2000 rpm, then hits a wall.
Holding it to the floor causes 'misses' and sputtering with a decrease
in power and speed until the pedal is let up on.
I have no way to verify fuel pressure other than to say this power issue
has been going on for several weeks with a 'stable' screw up. When
pumps go, they usually go sooner than later totally, but....
Things done:
Cap and rotor
Gas filter
Air filter new
Ran with open gas cap
Checked plugs, all 'very' even and evenly burned almost to the 'worn
out' point with a perfectly 'normal' coloring. Gap was almost 50, put
it back to 35.
That would go with the plug wires also checking out ok on my meter with
an ohm check. They are OEM 'lifetime' wires about 10 years old.
Checked and cleaned CPS (about 5 years old) with attention to the wire's
routing.
Cleaned main battery terminals and cable ends.
Cleaned TPS and checked it for smooth ohm reading all the way up.
Cleaned IAC connection, but not the unit itself??? Can that affect top end?
Cleaned coil connections and verified the meter readings. Seem ok. Got
1.5 ohm between the plus and minus pins, infinity between plus and case
and 'less than infinate' my books says between coil negative and high
tension post or 4.5 K ohm on the meter.
Unplugged EGR. No change so put it back.
Cleaned connections on the MAP sensor and verified the vacuum line.
I have to wait until later to have a friend go under to blow out the
fuel pump.
Mike
Mike Romain wrote:
> Ok, I am on a fishing expedition for likely things to check.
>
> Our 88 Cherokee with the 4.0 has lost power above half throttle. It
> goes fine up to that point, then just bogs, no matter what gear it is
> in. It has been neglected for 4 years as far as tuning goes due to me
> not being up to it.
>
> I first changed out the 'very' dirty distributor cap and rotor which
> made starting 'much' faster and smoother.
>
> I then changed the gas filter because it was once again rusted to the
> rot point after about 8 years.
>
> Air filter is new.
>
> I cleaned the connections on the TPS and IAC and verified the TPS
> doesn't have any 'dead' spots with my meter.
>
> I cleaned the CPS and coil connections also.
>
> No joy on any of that.
>
> I have been having some cold idle issues and have been thinking on
> cleaning the IAC, but don't know if that will have a top end effect or not.
>
> I am also thinking on unplugging the EGR just to make sure it isn't
> blown vacuum wise because it only bogs under throttle when things like
> the EGR are active.
>
> Any other ideas?
>
> Mike
> 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
> 88 Cherokee 235 BFG AT's
> Canadian Off Road Trips Photos: Non members can still view!
> Jan/06 http://www.imagestation.com/album/pi...?id=2115147590
> (More Off Road album links at bottom of the view page)
Have a fast idle (2000 rpm) issue when first started that mellows down.
It seems to be an RPM limiter under load.
If floored in neutral, the engine will die, it will not catch back as
the rpm comes down unless the pedal is let up on.
If coaxed up in neutral the engine will rev high.
When in 1st, it picks up fast to about 2000 rpm, then hits a wall.
Holding it to the floor causes 'misses' and sputtering with a decrease
in power and speed until the pedal is let up on.
I have no way to verify fuel pressure other than to say this power issue
has been going on for several weeks with a 'stable' screw up. When
pumps go, they usually go sooner than later totally, but....
Things done:
Cap and rotor
Gas filter
Air filter new
Ran with open gas cap
Checked plugs, all 'very' even and evenly burned almost to the 'worn
out' point with a perfectly 'normal' coloring. Gap was almost 50, put
it back to 35.
That would go with the plug wires also checking out ok on my meter with
an ohm check. They are OEM 'lifetime' wires about 10 years old.
Checked and cleaned CPS (about 5 years old) with attention to the wire's
routing.
Cleaned main battery terminals and cable ends.
Cleaned TPS and checked it for smooth ohm reading all the way up.
Cleaned IAC connection, but not the unit itself??? Can that affect top end?
Cleaned coil connections and verified the meter readings. Seem ok. Got
1.5 ohm between the plus and minus pins, infinity between plus and case
and 'less than infinate' my books says between coil negative and high
tension post or 4.5 K ohm on the meter.
Unplugged EGR. No change so put it back.
Cleaned connections on the MAP sensor and verified the vacuum line.
I have to wait until later to have a friend go under to blow out the
fuel pump.
Mike
Mike Romain wrote:
> Ok, I am on a fishing expedition for likely things to check.
>
> Our 88 Cherokee with the 4.0 has lost power above half throttle. It
> goes fine up to that point, then just bogs, no matter what gear it is
> in. It has been neglected for 4 years as far as tuning goes due to me
> not being up to it.
>
> I first changed out the 'very' dirty distributor cap and rotor which
> made starting 'much' faster and smoother.
>
> I then changed the gas filter because it was once again rusted to the
> rot point after about 8 years.
>
> Air filter is new.
>
> I cleaned the connections on the TPS and IAC and verified the TPS
> doesn't have any 'dead' spots with my meter.
>
> I cleaned the CPS and coil connections also.
>
> No joy on any of that.
>
> I have been having some cold idle issues and have been thinking on
> cleaning the IAC, but don't know if that will have a top end effect or not.
>
> I am also thinking on unplugging the EGR just to make sure it isn't
> blown vacuum wise because it only bogs under throttle when things like
> the EGR are active.
>
> Any other ideas?
>
> Mike
> 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
> 88 Cherokee 235 BFG AT's
> Canadian Off Road Trips Photos: Non members can still view!
> Jan/06 http://www.imagestation.com/album/pi...?id=2115147590
> (More Off Road album links at bottom of the view page)
Guest
Posts: n/a
Re: Lost top end power in 88 Cherokee 4.0.- Update
On Mon, 28 May 2007 13:57:17 -0400, Mike Romain <romainm@sympatico.ca>
wrote:
>Still no joy.
>
>Have a fast idle (2000 rpm) issue when first started that mellows down.
>
>It seems to be an RPM limiter under load.
>
>If floored in neutral, the engine will die, it will not catch back as
>the rpm comes down unless the pedal is let up on.
>
>If coaxed up in neutral the engine will rev high.
>
>When in 1st, it picks up fast to about 2000 rpm, then hits a wall.
>Holding it to the floor causes 'misses' and sputtering with a decrease
>in power and speed until the pedal is let up on.
>
>I have no way to verify fuel pressure other than to say this power issue
>has been going on for several weeks with a 'stable' screw up. When
>pumps go, they usually go sooner than later totally, but....
>
>Things done:
>
>Cap and rotor
>
>Gas filter
>
>Air filter new
>
>Ran with open gas cap
>
>Checked plugs, all 'very' even and evenly burned almost to the 'worn
>out' point with a perfectly 'normal' coloring. Gap was almost 50, put
>it back to 35.
>
>That would go with the plug wires also checking out ok on my meter with
>an ohm check. They are OEM 'lifetime' wires about 10 years old.
>Checked and cleaned CPS (about 5 years old) with attention to the wire's
>routing.
>
>Cleaned main battery terminals and cable ends.
>
>Cleaned TPS and checked it for smooth ohm reading all the way up.
>
>Cleaned IAC connection, but not the unit itself??? Can that affect top end?
>
>Cleaned coil connections and verified the meter readings. Seem ok. Got
>1.5 ohm between the plus and minus pins, infinity between plus and case
>and 'less than infinate' my books says between coil negative and high
>tension post or 4.5 K ohm on the meter.
>
>Unplugged EGR. No change so put it back.
>
>Cleaned connections on the MAP sensor and verified the vacuum line.
>
>I have to wait until later to have a friend go under to blow out the
>fuel pump.
The anti drain back check valve in the pump will make it difficult, if
not impossible to blow back through the pump. However, if it's easy to
blow back through it would indicate the the rubber hose from the pump
to the sending unit outlet has come loose or failed. Very common and
most likely cause of the problem you describe.
You could also be describing an ignition coil failure. Even if your
measurements look good, and it appears to create a strong spark, it
could still be shorted internally, causing your problem under load.
You'd need a scope to see it though.
>
>Mike
>
>Mike Romain wrote:
>> Ok, I am on a fishing expedition for likely things to check.
>>
>> Our 88 Cherokee with the 4.0 has lost power above half throttle. It
>> goes fine up to that point, then just bogs, no matter what gear it is
>> in. It has been neglected for 4 years as far as tuning goes due to me
>> not being up to it.
>>
>> I first changed out the 'very' dirty distributor cap and rotor which
>> made starting 'much' faster and smoother.
>>
>> I then changed the gas filter because it was once again rusted to the
>> rot point after about 8 years.
>>
>> Air filter is new.
>>
>> I cleaned the connections on the TPS and IAC and verified the TPS
>> doesn't have any 'dead' spots with my meter.
>>
>> I cleaned the CPS and coil connections also.
>>
>> No joy on any of that.
>>
>> I have been having some cold idle issues and have been thinking on
>> cleaning the IAC, but don't know if that will have a top end effect or not.
>>
>> I am also thinking on unplugging the EGR just to make sure it isn't
>> blown vacuum wise because it only bogs under throttle when things like
>> the EGR are active.
>>
>> Any other ideas?
>>
>> Mike
>> 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
>> 88 Cherokee 235 BFG AT's
>> Canadian Off Road Trips Photos: Non members can still view!
>> Jan/06 http://www.imagestation.com/album/pi...?id=2115147590
>> (More Off Road album links at bottom of the view page)
wrote:
>Still no joy.
>
>Have a fast idle (2000 rpm) issue when first started that mellows down.
>
>It seems to be an RPM limiter under load.
>
>If floored in neutral, the engine will die, it will not catch back as
>the rpm comes down unless the pedal is let up on.
>
>If coaxed up in neutral the engine will rev high.
>
>When in 1st, it picks up fast to about 2000 rpm, then hits a wall.
>Holding it to the floor causes 'misses' and sputtering with a decrease
>in power and speed until the pedal is let up on.
>
>I have no way to verify fuel pressure other than to say this power issue
>has been going on for several weeks with a 'stable' screw up. When
>pumps go, they usually go sooner than later totally, but....
>
>Things done:
>
>Cap and rotor
>
>Gas filter
>
>Air filter new
>
>Ran with open gas cap
>
>Checked plugs, all 'very' even and evenly burned almost to the 'worn
>out' point with a perfectly 'normal' coloring. Gap was almost 50, put
>it back to 35.
>
>That would go with the plug wires also checking out ok on my meter with
>an ohm check. They are OEM 'lifetime' wires about 10 years old.
>Checked and cleaned CPS (about 5 years old) with attention to the wire's
>routing.
>
>Cleaned main battery terminals and cable ends.
>
>Cleaned TPS and checked it for smooth ohm reading all the way up.
>
>Cleaned IAC connection, but not the unit itself??? Can that affect top end?
>
>Cleaned coil connections and verified the meter readings. Seem ok. Got
>1.5 ohm between the plus and minus pins, infinity between plus and case
>and 'less than infinate' my books says between coil negative and high
>tension post or 4.5 K ohm on the meter.
>
>Unplugged EGR. No change so put it back.
>
>Cleaned connections on the MAP sensor and verified the vacuum line.
>
>I have to wait until later to have a friend go under to blow out the
>fuel pump.
The anti drain back check valve in the pump will make it difficult, if
not impossible to blow back through the pump. However, if it's easy to
blow back through it would indicate the the rubber hose from the pump
to the sending unit outlet has come loose or failed. Very common and
most likely cause of the problem you describe.
You could also be describing an ignition coil failure. Even if your
measurements look good, and it appears to create a strong spark, it
could still be shorted internally, causing your problem under load.
You'd need a scope to see it though.
>
>Mike
>
>Mike Romain wrote:
>> Ok, I am on a fishing expedition for likely things to check.
>>
>> Our 88 Cherokee with the 4.0 has lost power above half throttle. It
>> goes fine up to that point, then just bogs, no matter what gear it is
>> in. It has been neglected for 4 years as far as tuning goes due to me
>> not being up to it.
>>
>> I first changed out the 'very' dirty distributor cap and rotor which
>> made starting 'much' faster and smoother.
>>
>> I then changed the gas filter because it was once again rusted to the
>> rot point after about 8 years.
>>
>> Air filter is new.
>>
>> I cleaned the connections on the TPS and IAC and verified the TPS
>> doesn't have any 'dead' spots with my meter.
>>
>> I cleaned the CPS and coil connections also.
>>
>> No joy on any of that.
>>
>> I have been having some cold idle issues and have been thinking on
>> cleaning the IAC, but don't know if that will have a top end effect or not.
>>
>> I am also thinking on unplugging the EGR just to make sure it isn't
>> blown vacuum wise because it only bogs under throttle when things like
>> the EGR are active.
>>
>> Any other ideas?
>>
>> Mike
>> 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
>> 88 Cherokee 235 BFG AT's
>> Canadian Off Road Trips Photos: Non members can still view!
>> Jan/06 http://www.imagestation.com/album/pi...?id=2115147590
>> (More Off Road album links at bottom of the view page)
Guest
Posts: n/a
Re: Lost top end power in 88 Cherokee 4.0.- Update
On Mon, 28 May 2007 13:57:17 -0400, Mike Romain <romainm@sympatico.ca>
wrote:
>Still no joy.
>
>Have a fast idle (2000 rpm) issue when first started that mellows down.
>
>It seems to be an RPM limiter under load.
>
>If floored in neutral, the engine will die, it will not catch back as
>the rpm comes down unless the pedal is let up on.
>
>If coaxed up in neutral the engine will rev high.
>
>When in 1st, it picks up fast to about 2000 rpm, then hits a wall.
>Holding it to the floor causes 'misses' and sputtering with a decrease
>in power and speed until the pedal is let up on.
>
>I have no way to verify fuel pressure other than to say this power issue
>has been going on for several weeks with a 'stable' screw up. When
>pumps go, they usually go sooner than later totally, but....
>
>Things done:
>
>Cap and rotor
>
>Gas filter
>
>Air filter new
>
>Ran with open gas cap
>
>Checked plugs, all 'very' even and evenly burned almost to the 'worn
>out' point with a perfectly 'normal' coloring. Gap was almost 50, put
>it back to 35.
>
>That would go with the plug wires also checking out ok on my meter with
>an ohm check. They are OEM 'lifetime' wires about 10 years old.
>Checked and cleaned CPS (about 5 years old) with attention to the wire's
>routing.
>
>Cleaned main battery terminals and cable ends.
>
>Cleaned TPS and checked it for smooth ohm reading all the way up.
>
>Cleaned IAC connection, but not the unit itself??? Can that affect top end?
>
>Cleaned coil connections and verified the meter readings. Seem ok. Got
>1.5 ohm between the plus and minus pins, infinity between plus and case
>and 'less than infinate' my books says between coil negative and high
>tension post or 4.5 K ohm on the meter.
>
>Unplugged EGR. No change so put it back.
>
>Cleaned connections on the MAP sensor and verified the vacuum line.
>
>I have to wait until later to have a friend go under to blow out the
>fuel pump.
The anti drain back check valve in the pump will make it difficult, if
not impossible to blow back through the pump. However, if it's easy to
blow back through it would indicate the the rubber hose from the pump
to the sending unit outlet has come loose or failed. Very common and
most likely cause of the problem you describe.
You could also be describing an ignition coil failure. Even if your
measurements look good, and it appears to create a strong spark, it
could still be shorted internally, causing your problem under load.
You'd need a scope to see it though.
>
>Mike
>
>Mike Romain wrote:
>> Ok, I am on a fishing expedition for likely things to check.
>>
>> Our 88 Cherokee with the 4.0 has lost power above half throttle. It
>> goes fine up to that point, then just bogs, no matter what gear it is
>> in. It has been neglected for 4 years as far as tuning goes due to me
>> not being up to it.
>>
>> I first changed out the 'very' dirty distributor cap and rotor which
>> made starting 'much' faster and smoother.
>>
>> I then changed the gas filter because it was once again rusted to the
>> rot point after about 8 years.
>>
>> Air filter is new.
>>
>> I cleaned the connections on the TPS and IAC and verified the TPS
>> doesn't have any 'dead' spots with my meter.
>>
>> I cleaned the CPS and coil connections also.
>>
>> No joy on any of that.
>>
>> I have been having some cold idle issues and have been thinking on
>> cleaning the IAC, but don't know if that will have a top end effect or not.
>>
>> I am also thinking on unplugging the EGR just to make sure it isn't
>> blown vacuum wise because it only bogs under throttle when things like
>> the EGR are active.
>>
>> Any other ideas?
>>
>> Mike
>> 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
>> 88 Cherokee 235 BFG AT's
>> Canadian Off Road Trips Photos: Non members can still view!
>> Jan/06 http://www.imagestation.com/album/pi...?id=2115147590
>> (More Off Road album links at bottom of the view page)
wrote:
>Still no joy.
>
>Have a fast idle (2000 rpm) issue when first started that mellows down.
>
>It seems to be an RPM limiter under load.
>
>If floored in neutral, the engine will die, it will not catch back as
>the rpm comes down unless the pedal is let up on.
>
>If coaxed up in neutral the engine will rev high.
>
>When in 1st, it picks up fast to about 2000 rpm, then hits a wall.
>Holding it to the floor causes 'misses' and sputtering with a decrease
>in power and speed until the pedal is let up on.
>
>I have no way to verify fuel pressure other than to say this power issue
>has been going on for several weeks with a 'stable' screw up. When
>pumps go, they usually go sooner than later totally, but....
>
>Things done:
>
>Cap and rotor
>
>Gas filter
>
>Air filter new
>
>Ran with open gas cap
>
>Checked plugs, all 'very' even and evenly burned almost to the 'worn
>out' point with a perfectly 'normal' coloring. Gap was almost 50, put
>it back to 35.
>
>That would go with the plug wires also checking out ok on my meter with
>an ohm check. They are OEM 'lifetime' wires about 10 years old.
>Checked and cleaned CPS (about 5 years old) with attention to the wire's
>routing.
>
>Cleaned main battery terminals and cable ends.
>
>Cleaned TPS and checked it for smooth ohm reading all the way up.
>
>Cleaned IAC connection, but not the unit itself??? Can that affect top end?
>
>Cleaned coil connections and verified the meter readings. Seem ok. Got
>1.5 ohm between the plus and minus pins, infinity between plus and case
>and 'less than infinate' my books says between coil negative and high
>tension post or 4.5 K ohm on the meter.
>
>Unplugged EGR. No change so put it back.
>
>Cleaned connections on the MAP sensor and verified the vacuum line.
>
>I have to wait until later to have a friend go under to blow out the
>fuel pump.
The anti drain back check valve in the pump will make it difficult, if
not impossible to blow back through the pump. However, if it's easy to
blow back through it would indicate the the rubber hose from the pump
to the sending unit outlet has come loose or failed. Very common and
most likely cause of the problem you describe.
You could also be describing an ignition coil failure. Even if your
measurements look good, and it appears to create a strong spark, it
could still be shorted internally, causing your problem under load.
You'd need a scope to see it though.
>
>Mike
>
>Mike Romain wrote:
>> Ok, I am on a fishing expedition for likely things to check.
>>
>> Our 88 Cherokee with the 4.0 has lost power above half throttle. It
>> goes fine up to that point, then just bogs, no matter what gear it is
>> in. It has been neglected for 4 years as far as tuning goes due to me
>> not being up to it.
>>
>> I first changed out the 'very' dirty distributor cap and rotor which
>> made starting 'much' faster and smoother.
>>
>> I then changed the gas filter because it was once again rusted to the
>> rot point after about 8 years.
>>
>> Air filter is new.
>>
>> I cleaned the connections on the TPS and IAC and verified the TPS
>> doesn't have any 'dead' spots with my meter.
>>
>> I cleaned the CPS and coil connections also.
>>
>> No joy on any of that.
>>
>> I have been having some cold idle issues and have been thinking on
>> cleaning the IAC, but don't know if that will have a top end effect or not.
>>
>> I am also thinking on unplugging the EGR just to make sure it isn't
>> blown vacuum wise because it only bogs under throttle when things like
>> the EGR are active.
>>
>> Any other ideas?
>>
>> Mike
>> 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
>> 88 Cherokee 235 BFG AT's
>> Canadian Off Road Trips Photos: Non members can still view!
>> Jan/06 http://www.imagestation.com/album/pi...?id=2115147590
>> (More Off Road album links at bottom of the view page)
Guest
Posts: n/a
Re: Lost top end power in 88 Cherokee 4.0.- Update
On Mon, 28 May 2007 13:57:17 -0400, Mike Romain <romainm@sympatico.ca>
wrote:
>Still no joy.
>
>Have a fast idle (2000 rpm) issue when first started that mellows down.
>
>It seems to be an RPM limiter under load.
>
>If floored in neutral, the engine will die, it will not catch back as
>the rpm comes down unless the pedal is let up on.
>
>If coaxed up in neutral the engine will rev high.
>
>When in 1st, it picks up fast to about 2000 rpm, then hits a wall.
>Holding it to the floor causes 'misses' and sputtering with a decrease
>in power and speed until the pedal is let up on.
>
>I have no way to verify fuel pressure other than to say this power issue
>has been going on for several weeks with a 'stable' screw up. When
>pumps go, they usually go sooner than later totally, but....
>
>Things done:
>
>Cap and rotor
>
>Gas filter
>
>Air filter new
>
>Ran with open gas cap
>
>Checked plugs, all 'very' even and evenly burned almost to the 'worn
>out' point with a perfectly 'normal' coloring. Gap was almost 50, put
>it back to 35.
>
>That would go with the plug wires also checking out ok on my meter with
>an ohm check. They are OEM 'lifetime' wires about 10 years old.
>Checked and cleaned CPS (about 5 years old) with attention to the wire's
>routing.
>
>Cleaned main battery terminals and cable ends.
>
>Cleaned TPS and checked it for smooth ohm reading all the way up.
>
>Cleaned IAC connection, but not the unit itself??? Can that affect top end?
>
>Cleaned coil connections and verified the meter readings. Seem ok. Got
>1.5 ohm between the plus and minus pins, infinity between plus and case
>and 'less than infinate' my books says between coil negative and high
>tension post or 4.5 K ohm on the meter.
>
>Unplugged EGR. No change so put it back.
>
>Cleaned connections on the MAP sensor and verified the vacuum line.
>
>I have to wait until later to have a friend go under to blow out the
>fuel pump.
The anti drain back check valve in the pump will make it difficult, if
not impossible to blow back through the pump. However, if it's easy to
blow back through it would indicate the the rubber hose from the pump
to the sending unit outlet has come loose or failed. Very common and
most likely cause of the problem you describe.
You could also be describing an ignition coil failure. Even if your
measurements look good, and it appears to create a strong spark, it
could still be shorted internally, causing your problem under load.
You'd need a scope to see it though.
>
>Mike
>
>Mike Romain wrote:
>> Ok, I am on a fishing expedition for likely things to check.
>>
>> Our 88 Cherokee with the 4.0 has lost power above half throttle. It
>> goes fine up to that point, then just bogs, no matter what gear it is
>> in. It has been neglected for 4 years as far as tuning goes due to me
>> not being up to it.
>>
>> I first changed out the 'very' dirty distributor cap and rotor which
>> made starting 'much' faster and smoother.
>>
>> I then changed the gas filter because it was once again rusted to the
>> rot point after about 8 years.
>>
>> Air filter is new.
>>
>> I cleaned the connections on the TPS and IAC and verified the TPS
>> doesn't have any 'dead' spots with my meter.
>>
>> I cleaned the CPS and coil connections also.
>>
>> No joy on any of that.
>>
>> I have been having some cold idle issues and have been thinking on
>> cleaning the IAC, but don't know if that will have a top end effect or not.
>>
>> I am also thinking on unplugging the EGR just to make sure it isn't
>> blown vacuum wise because it only bogs under throttle when things like
>> the EGR are active.
>>
>> Any other ideas?
>>
>> Mike
>> 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
>> 88 Cherokee 235 BFG AT's
>> Canadian Off Road Trips Photos: Non members can still view!
>> Jan/06 http://www.imagestation.com/album/pi...?id=2115147590
>> (More Off Road album links at bottom of the view page)
wrote:
>Still no joy.
>
>Have a fast idle (2000 rpm) issue when first started that mellows down.
>
>It seems to be an RPM limiter under load.
>
>If floored in neutral, the engine will die, it will not catch back as
>the rpm comes down unless the pedal is let up on.
>
>If coaxed up in neutral the engine will rev high.
>
>When in 1st, it picks up fast to about 2000 rpm, then hits a wall.
>Holding it to the floor causes 'misses' and sputtering with a decrease
>in power and speed until the pedal is let up on.
>
>I have no way to verify fuel pressure other than to say this power issue
>has been going on for several weeks with a 'stable' screw up. When
>pumps go, they usually go sooner than later totally, but....
>
>Things done:
>
>Cap and rotor
>
>Gas filter
>
>Air filter new
>
>Ran with open gas cap
>
>Checked plugs, all 'very' even and evenly burned almost to the 'worn
>out' point with a perfectly 'normal' coloring. Gap was almost 50, put
>it back to 35.
>
>That would go with the plug wires also checking out ok on my meter with
>an ohm check. They are OEM 'lifetime' wires about 10 years old.
>Checked and cleaned CPS (about 5 years old) with attention to the wire's
>routing.
>
>Cleaned main battery terminals and cable ends.
>
>Cleaned TPS and checked it for smooth ohm reading all the way up.
>
>Cleaned IAC connection, but not the unit itself??? Can that affect top end?
>
>Cleaned coil connections and verified the meter readings. Seem ok. Got
>1.5 ohm between the plus and minus pins, infinity between plus and case
>and 'less than infinate' my books says between coil negative and high
>tension post or 4.5 K ohm on the meter.
>
>Unplugged EGR. No change so put it back.
>
>Cleaned connections on the MAP sensor and verified the vacuum line.
>
>I have to wait until later to have a friend go under to blow out the
>fuel pump.
The anti drain back check valve in the pump will make it difficult, if
not impossible to blow back through the pump. However, if it's easy to
blow back through it would indicate the the rubber hose from the pump
to the sending unit outlet has come loose or failed. Very common and
most likely cause of the problem you describe.
You could also be describing an ignition coil failure. Even if your
measurements look good, and it appears to create a strong spark, it
could still be shorted internally, causing your problem under load.
You'd need a scope to see it though.
>
>Mike
>
>Mike Romain wrote:
>> Ok, I am on a fishing expedition for likely things to check.
>>
>> Our 88 Cherokee with the 4.0 has lost power above half throttle. It
>> goes fine up to that point, then just bogs, no matter what gear it is
>> in. It has been neglected for 4 years as far as tuning goes due to me
>> not being up to it.
>>
>> I first changed out the 'very' dirty distributor cap and rotor which
>> made starting 'much' faster and smoother.
>>
>> I then changed the gas filter because it was once again rusted to the
>> rot point after about 8 years.
>>
>> Air filter is new.
>>
>> I cleaned the connections on the TPS and IAC and verified the TPS
>> doesn't have any 'dead' spots with my meter.
>>
>> I cleaned the CPS and coil connections also.
>>
>> No joy on any of that.
>>
>> I have been having some cold idle issues and have been thinking on
>> cleaning the IAC, but don't know if that will have a top end effect or not.
>>
>> I am also thinking on unplugging the EGR just to make sure it isn't
>> blown vacuum wise because it only bogs under throttle when things like
>> the EGR are active.
>>
>> Any other ideas?
>>
>> Mike
>> 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
>> 88 Cherokee 235 BFG AT's
>> Canadian Off Road Trips Photos: Non members can still view!
>> Jan/06 http://www.imagestation.com/album/pi...?id=2115147590
>> (More Off Road album links at bottom of the view page)
Guest
Posts: n/a
Re: Lost top end power in 88 Cherokee 4.0.- Update
On Mon, 28 May 2007 13:57:17 -0400, Mike Romain <romainm@sympatico.ca>
wrote:
>Still no joy.
>
>Have a fast idle (2000 rpm) issue when first started that mellows down.
>
>It seems to be an RPM limiter under load.
>
>If floored in neutral, the engine will die, it will not catch back as
>the rpm comes down unless the pedal is let up on.
>
>If coaxed up in neutral the engine will rev high.
>
>When in 1st, it picks up fast to about 2000 rpm, then hits a wall.
>Holding it to the floor causes 'misses' and sputtering with a decrease
>in power and speed until the pedal is let up on.
>
>I have no way to verify fuel pressure other than to say this power issue
>has been going on for several weeks with a 'stable' screw up. When
>pumps go, they usually go sooner than later totally, but....
>
>Things done:
>
>Cap and rotor
>
>Gas filter
>
>Air filter new
>
>Ran with open gas cap
>
>Checked plugs, all 'very' even and evenly burned almost to the 'worn
>out' point with a perfectly 'normal' coloring. Gap was almost 50, put
>it back to 35.
>
>That would go with the plug wires also checking out ok on my meter with
>an ohm check. They are OEM 'lifetime' wires about 10 years old.
>Checked and cleaned CPS (about 5 years old) with attention to the wire's
>routing.
>
>Cleaned main battery terminals and cable ends.
>
>Cleaned TPS and checked it for smooth ohm reading all the way up.
>
>Cleaned IAC connection, but not the unit itself??? Can that affect top end?
>
>Cleaned coil connections and verified the meter readings. Seem ok. Got
>1.5 ohm between the plus and minus pins, infinity between plus and case
>and 'less than infinate' my books says between coil negative and high
>tension post or 4.5 K ohm on the meter.
>
>Unplugged EGR. No change so put it back.
>
>Cleaned connections on the MAP sensor and verified the vacuum line.
>
>I have to wait until later to have a friend go under to blow out the
>fuel pump.
The anti drain back check valve in the pump will make it difficult, if
not impossible to blow back through the pump. However, if it's easy to
blow back through it would indicate the the rubber hose from the pump
to the sending unit outlet has come loose or failed. Very common and
most likely cause of the problem you describe.
You could also be describing an ignition coil failure. Even if your
measurements look good, and it appears to create a strong spark, it
could still be shorted internally, causing your problem under load.
You'd need a scope to see it though.
>
>Mike
>
>Mike Romain wrote:
>> Ok, I am on a fishing expedition for likely things to check.
>>
>> Our 88 Cherokee with the 4.0 has lost power above half throttle. It
>> goes fine up to that point, then just bogs, no matter what gear it is
>> in. It has been neglected for 4 years as far as tuning goes due to me
>> not being up to it.
>>
>> I first changed out the 'very' dirty distributor cap and rotor which
>> made starting 'much' faster and smoother.
>>
>> I then changed the gas filter because it was once again rusted to the
>> rot point after about 8 years.
>>
>> Air filter is new.
>>
>> I cleaned the connections on the TPS and IAC and verified the TPS
>> doesn't have any 'dead' spots with my meter.
>>
>> I cleaned the CPS and coil connections also.
>>
>> No joy on any of that.
>>
>> I have been having some cold idle issues and have been thinking on
>> cleaning the IAC, but don't know if that will have a top end effect or not.
>>
>> I am also thinking on unplugging the EGR just to make sure it isn't
>> blown vacuum wise because it only bogs under throttle when things like
>> the EGR are active.
>>
>> Any other ideas?
>>
>> Mike
>> 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
>> 88 Cherokee 235 BFG AT's
>> Canadian Off Road Trips Photos: Non members can still view!
>> Jan/06 http://www.imagestation.com/album/pi...?id=2115147590
>> (More Off Road album links at bottom of the view page)
wrote:
>Still no joy.
>
>Have a fast idle (2000 rpm) issue when first started that mellows down.
>
>It seems to be an RPM limiter under load.
>
>If floored in neutral, the engine will die, it will not catch back as
>the rpm comes down unless the pedal is let up on.
>
>If coaxed up in neutral the engine will rev high.
>
>When in 1st, it picks up fast to about 2000 rpm, then hits a wall.
>Holding it to the floor causes 'misses' and sputtering with a decrease
>in power and speed until the pedal is let up on.
>
>I have no way to verify fuel pressure other than to say this power issue
>has been going on for several weeks with a 'stable' screw up. When
>pumps go, they usually go sooner than later totally, but....
>
>Things done:
>
>Cap and rotor
>
>Gas filter
>
>Air filter new
>
>Ran with open gas cap
>
>Checked plugs, all 'very' even and evenly burned almost to the 'worn
>out' point with a perfectly 'normal' coloring. Gap was almost 50, put
>it back to 35.
>
>That would go with the plug wires also checking out ok on my meter with
>an ohm check. They are OEM 'lifetime' wires about 10 years old.
>Checked and cleaned CPS (about 5 years old) with attention to the wire's
>routing.
>
>Cleaned main battery terminals and cable ends.
>
>Cleaned TPS and checked it for smooth ohm reading all the way up.
>
>Cleaned IAC connection, but not the unit itself??? Can that affect top end?
>
>Cleaned coil connections and verified the meter readings. Seem ok. Got
>1.5 ohm between the plus and minus pins, infinity between plus and case
>and 'less than infinate' my books says between coil negative and high
>tension post or 4.5 K ohm on the meter.
>
>Unplugged EGR. No change so put it back.
>
>Cleaned connections on the MAP sensor and verified the vacuum line.
>
>I have to wait until later to have a friend go under to blow out the
>fuel pump.
The anti drain back check valve in the pump will make it difficult, if
not impossible to blow back through the pump. However, if it's easy to
blow back through it would indicate the the rubber hose from the pump
to the sending unit outlet has come loose or failed. Very common and
most likely cause of the problem you describe.
You could also be describing an ignition coil failure. Even if your
measurements look good, and it appears to create a strong spark, it
could still be shorted internally, causing your problem under load.
You'd need a scope to see it though.
>
>Mike
>
>Mike Romain wrote:
>> Ok, I am on a fishing expedition for likely things to check.
>>
>> Our 88 Cherokee with the 4.0 has lost power above half throttle. It
>> goes fine up to that point, then just bogs, no matter what gear it is
>> in. It has been neglected for 4 years as far as tuning goes due to me
>> not being up to it.
>>
>> I first changed out the 'very' dirty distributor cap and rotor which
>> made starting 'much' faster and smoother.
>>
>> I then changed the gas filter because it was once again rusted to the
>> rot point after about 8 years.
>>
>> Air filter is new.
>>
>> I cleaned the connections on the TPS and IAC and verified the TPS
>> doesn't have any 'dead' spots with my meter.
>>
>> I cleaned the CPS and coil connections also.
>>
>> No joy on any of that.
>>
>> I have been having some cold idle issues and have been thinking on
>> cleaning the IAC, but don't know if that will have a top end effect or not.
>>
>> I am also thinking on unplugging the EGR just to make sure it isn't
>> blown vacuum wise because it only bogs under throttle when things like
>> the EGR are active.
>>
>> Any other ideas?
>>
>> Mike
>> 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
>> 88 Cherokee 235 BFG AT's
>> Canadian Off Road Trips Photos: Non members can still view!
>> Jan/06 http://www.imagestation.com/album/pi...?id=2115147590
>> (More Off Road album links at bottom of the view page)