Re: Re: Lost top end power in 88 Cherokee 4.0.
 

On Sun, 27 May 2007 15:23:32 -0400, Mike Romain <romainm@sympatico.ca>
wrote:

>Stalls and stops and sputters until the gas pedal is let up on.
>
>No backfires.
>
>EGR now unplugged.


Run it hard and make it bog and them pull over and remove a plug and
see if it is white or sooty. I tend to think you are getting a fuel
starvation here that surfaces at higher power settings. Hard to be
sure without feeling it but the plugs would confirm a lean out. Might
start by changing fuel filter like someone else suggested and maybe a
fuel pressure check too.
-----------------
TheSnoMan.com

Re: Re: Lost top end power in 88 Cherokee 4.0.
 

On Sun, 27 May 2007 15:23:32 -0400, Mike Romain <romainm@sympatico.ca>
wrote:

>Stalls and stops and sputters until the gas pedal is let up on.
>
>No backfires.
>
>EGR now unplugged.


Run it hard and make it bog and them pull over and remove a plug and
see if it is white or sooty. I tend to think you are getting a fuel
starvation here that surfaces at higher power settings. Hard to be
sure without feeling it but the plugs would confirm a lean out. Might
start by changing fuel filter like someone else suggested and maybe a
fuel pressure check too.
-----------------
TheSnoMan.com

Re: Re: Lost top end power in 88 Cherokee 4.0.
 

On Sun, 27 May 2007 15:23:32 -0400, Mike Romain <romainm@sympatico.ca>
wrote:

>Stalls and stops and sputters until the gas pedal is let up on.
>
>No backfires.
>
>EGR now unplugged.


Run it hard and make it bog and them pull over and remove a plug and
see if it is white or sooty. I tend to think you are getting a fuel
starvation here that surfaces at higher power settings. Hard to be
sure without feeling it but the plugs would confirm a lean out. Might
start by changing fuel filter like someone else suggested and maybe a
fuel pressure check too.
-----------------
TheSnoMan.com

Re: Re: Lost top end power in 88 Cherokee 4.0.
 

SnoMan <admin@snoman.com> wrote:

> Run it hard and make it bog and them pull over and remove a plug
> and see if it is white or sooty. I tend to think you are getting a
> fuel starvation here that surfaces at higher power settings. Hard
> to be sure without feeling it but the plugs would confirm a lean
> out. Might start by changing fuel filter like someone else
> suggested and maybe a fuel pressure check too.

Don't disagree with you at all but the OP says he already replaced the
fuel filter, my question: Is there another filter somewhere?

I had a Cherokee years back but I no longer have the service manuals so
I don't know if there is another filter.

What about the fuel vent? That's easy to check by driving with the gas
cap removed.

--
XS11E, Killing all posts from Google Groups
The Usenet Improvement Project: http://blinkynet.net/comp/uip5.html

Re: Re: Lost top end power in 88 Cherokee 4.0.
 

SnoMan <admin@snoman.com> wrote:

> Run it hard and make it bog and them pull over and remove a plug
> and see if it is white or sooty. I tend to think you are getting a
> fuel starvation here that surfaces at higher power settings. Hard
> to be sure without feeling it but the plugs would confirm a lean
> out. Might start by changing fuel filter like someone else
> suggested and maybe a fuel pressure check too.

Don't disagree with you at all but the OP says he already replaced the
fuel filter, my question: Is there another filter somewhere?

I had a Cherokee years back but I no longer have the service manuals so
I don't know if there is another filter.

What about the fuel vent? That's easy to check by driving with the gas
cap removed.

--
XS11E, Killing all posts from Google Groups
The Usenet Improvement Project: http://blinkynet.net/comp/uip5.html

Re: Re: Lost top end power in 88 Cherokee 4.0.
 

SnoMan <admin@snoman.com> wrote:

> Run it hard and make it bog and them pull over and remove a plug
> and see if it is white or sooty. I tend to think you are getting a
> fuel starvation here that surfaces at higher power settings. Hard
> to be sure without feeling it but the plugs would confirm a lean
> out. Might start by changing fuel filter like someone else
> suggested and maybe a fuel pressure check too.

Don't disagree with you at all but the OP says he already replaced the
fuel filter, my question: Is there another filter somewhere?

I had a Cherokee years back but I no longer have the service manuals so
I don't know if there is another filter.

What about the fuel vent? That's easy to check by driving with the gas
cap removed.

--
XS11E, Killing all posts from Google Groups
The Usenet Improvement Project: http://blinkynet.net/comp/uip5.html

Re: Re: Lost top end power in 88 Cherokee 4.0.
 

SnoMan <admin@snoman.com> wrote:

> Run it hard and make it bog and them pull over and remove a plug
> and see if it is white or sooty. I tend to think you are getting a
> fuel starvation here that surfaces at higher power settings. Hard
> to be sure without feeling it but the plugs would confirm a lean
> out. Might start by changing fuel filter like someone else
> suggested and maybe a fuel pressure check too.

Don't disagree with you at all but the OP says he already replaced the
fuel filter, my question: Is there another filter somewhere?

I had a Cherokee years back but I no longer have the service manuals so
I don't know if there is another filter.

What about the fuel vent? That's easy to check by driving with the gas
cap removed.

--
XS11E, Killing all posts from Google Groups
The Usenet Improvement Project: http://blinkynet.net/comp/uip5.html

Re: Lost top end power in 88 Cherokee 4.0.
 

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?

I've had this situation twice. First time was a dying fuel pump - and it
progressed to dead pretty quickly. Second was a shorted cable to the CPS.
Didn't tie it back properly and the exhaust got it. Same symptoms, except
my max RPM was 1000-1200 RPM, period. Crept home at idle <g>.
--
Will Honea

Re: Lost top end power in 88 Cherokee 4.0.
 

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?

I've had this situation twice. First time was a dying fuel pump - and it
progressed to dead pretty quickly. Second was a shorted cable to the CPS.
Didn't tie it back properly and the exhaust got it. Same symptoms, except
my max RPM was 1000-1200 RPM, period. Crept home at idle <g>.
--
Will Honea

Re: Lost top end power in 88 Cherokee 4.0.
 

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?

I've had this situation twice. First time was a dying fuel pump - and it
progressed to dead pretty quickly. Second was a shorted cable to the CPS.
Didn't tie it back properly and the exhaust got it. Same symptoms, except
my max RPM was 1000-1200 RPM, period. Crept home at idle <g>.
--
Will Honea