CADman

Here's my problem:

I am bringing an old '89 Cherokee Pioneer 4.0L Automatic back to life
while I rebuild my '87 Laredo 4.0L engine (got about 250,000 mile on
it before it died). The '89 Pioneer was very clean inside and body
straight, but the engine compartment was a horrible dirty mess.

The problem is that, when I cold start, it runs fine (about 1200 rpm),
then after about 46-60 seconds, rpm's drop badly to near stall (200
rmp's or so) and runs rough. After it warms up, runs fine, smooth
acceleration and has plenty of power AND just passed California Smog
Test.

Also, after a good run when warm, if I stop and shut down engine for
10-15 minutes or so and restart, it runs super rough (like on half the
cylinders) until warm and reving the engine again.

Here's what I've done:

Thoroughly cleaned all connectors (TPS, IAC, CPS, O2 Sensor, Relays)
and anything I could see and get my hands on.

Thoroughly cleaned Throttle Body, IAC and IAC Port, Idle Air Port, and
re-installed TBS with new gasket.

Tightened exhaust/manifold bolts. They were a bit loose.

Replaced MAP sensor with new part.

Have tried two different used but cleaned IAC's. Same result.

Compression is 140-150 cold on all cylinders.

Set TPS to spec.

New Distributor Cap, Wires, Plugs.

Brakes and Booster seem OK (though the fluid was, still is, mocka
brown. Full flush is next on the list of to do's). Though when in
neutral, pumping the breaks causes about a 300 rpm increase. Is that
normal? hmmm...

O2 sensor test reads 6 ohm. Dead center on spec.

EGR valve appears to be working OK. By the way, the 89 has a smaller
EGR than my 87 and it has a Regulator upstream of the EGR. Is this
the correct configuration? My Vacuum diagragm (chiltons) does not
show the Regulator but the Jeep Dealer says its fine. hmmm...

Any ideas what could be causing this problem? I sure could used your
help with this one.

One other aggrevation, the Fuel Gage at 1/8th tank still has about 6
gallons in it. Any way to adjust the gage in the dash?

Thanks in advance...

Mark

PS: First time on the list.. Thanks guys (and gals), it's a great
help!!!

Dave

Did you check the Coolant Temperature Sensor?
Are you sure your heated 02 sensor is getting it's 12volts and ground? This
is what it sounds like to me, or maybe it is not working.
I think the dealer is still doing recalls on these 02s.
I found out about that after finding a stash of them for mine or for sale.
:-(

I think that valve for the EGR is called a transducer. I had to clean the
carbon out of mine to get it to vent properly. It would cause the EGR Valve
to stay open and the engine would try to stall.
--
later,
dave
88 XJ 4.0 auto
82 Wag Ltd. 360 auto (to be retired!) anyone interested, whole or parts?
88 FSJ-GW 360 auto (GRAND 88)
Chicago


"CADman" <marcad2000@dslextreme.com> wrote in message
news:edacf47c.0401141957.1d3043b4@posting.google.c om...
> Here's my problem:
>
> I am bringing an old '89 Cherokee Pioneer 4.0L Automatic back to life
> while I rebuild my '87 Laredo 4.0L engine (got about 250,000 mile on
> it before it died). The '89 Pioneer was very clean inside and body
> straight, but the engine compartment was a horrible dirty mess.
>
> The problem is that, when I cold start, it runs fine (about 1200 rpm),
> then after about 46-60 seconds, rpm's drop badly to near stall (200
> rmp's or so) and runs rough. After it warms up, runs fine, smooth
> acceleration and has plenty of power AND just passed California Smog
> Test.
>
> Also, after a good run when warm, if I stop and shut down engine for
> 10-15 minutes or so and restart, it runs super rough (like on half the
> cylinders) until warm and reving the engine again.
>
> Here's what I've done:
>
> Thoroughly cleaned all connectors (TPS, IAC, CPS, O2 Sensor, Relays)
> and anything I could see and get my hands on.
>
> Thoroughly cleaned Throttle Body, IAC and IAC Port, Idle Air Port, and
> re-installed TBS with new gasket.
>
> Tightened exhaust/manifold bolts. They were a bit loose.
>
> Replaced MAP sensor with new part.
>
> Have tried two different used but cleaned IAC's. Same result.
>
> Compression is 140-150 cold on all cylinders.
>
> Set TPS to spec.
>
> New Distributor Cap, Wires, Plugs.
>
> Brakes and Booster seem OK (though the fluid was, still is, mocka
> brown. Full flush is next on the list of to do's). Though when in
> neutral, pumping the breaks causes about a 300 rpm increase. Is that
> normal? hmmm...
>
> O2 sensor test reads 6 ohm. Dead center on spec.
>
> EGR valve appears to be working OK. By the way, the 89 has a smaller
> EGR than my 87 and it has a Regulator upstream of the EGR. Is this
> the correct configuration? My Vacuum diagragm (chiltons) does not
> show the Regulator but the Jeep Dealer says its fine. hmmm...
>
> Any ideas what could be causing this problem? I sure could used your
> help with this one.
>
> One other aggrevation, the Fuel Gage at 1/8th tank still has about 6
> gallons in it. Any way to adjust the gage in the dash?
>
> Thanks in advance...
>
> Mark
>
> PS: First time on the list.. Thanks guys (and gals), it's a great
> help!!!

Dave

Did you check the Coolant Temperature Sensor?
Are you sure your heated 02 sensor is getting it's 12volts and ground? This
is what it sounds like to me, or maybe it is not working.
I think the dealer is still doing recalls on these 02s.
I found out about that after finding a stash of them for mine or for sale.
:-(

I think that valve for the EGR is called a transducer. I had to clean the
carbon out of mine to get it to vent properly. It would cause the EGR Valve
to stay open and the engine would try to stall.
--
later,
dave
88 XJ 4.0 auto
82 Wag Ltd. 360 auto (to be retired!) anyone interested, whole or parts?
88 FSJ-GW 360 auto (GRAND 88)
Chicago


"CADman" <marcad2000@dslextreme.com> wrote in message
news:edacf47c.0401141957.1d3043b4@posting.google.c om...
> Here's my problem:
>
> I am bringing an old '89 Cherokee Pioneer 4.0L Automatic back to life
> while I rebuild my '87 Laredo 4.0L engine (got about 250,000 mile on
> it before it died). The '89 Pioneer was very clean inside and body
> straight, but the engine compartment was a horrible dirty mess.
>
> The problem is that, when I cold start, it runs fine (about 1200 rpm),
> then after about 46-60 seconds, rpm's drop badly to near stall (200
> rmp's or so) and runs rough. After it warms up, runs fine, smooth
> acceleration and has plenty of power AND just passed California Smog
> Test.
>
> Also, after a good run when warm, if I stop and shut down engine for
> 10-15 minutes or so and restart, it runs super rough (like on half the
> cylinders) until warm and reving the engine again.
>
> Here's what I've done:
>
> Thoroughly cleaned all connectors (TPS, IAC, CPS, O2 Sensor, Relays)
> and anything I could see and get my hands on.
>
> Thoroughly cleaned Throttle Body, IAC and IAC Port, Idle Air Port, and
> re-installed TBS with new gasket.
>
> Tightened exhaust/manifold bolts. They were a bit loose.
>
> Replaced MAP sensor with new part.
>
> Have tried two different used but cleaned IAC's. Same result.
>
> Compression is 140-150 cold on all cylinders.
>
> Set TPS to spec.
>
> New Distributor Cap, Wires, Plugs.
>
> Brakes and Booster seem OK (though the fluid was, still is, mocka
> brown. Full flush is next on the list of to do's). Though when in
> neutral, pumping the breaks causes about a 300 rpm increase. Is that
> normal? hmmm...
>
> O2 sensor test reads 6 ohm. Dead center on spec.
>
> EGR valve appears to be working OK. By the way, the 89 has a smaller
> EGR than my 87 and it has a Regulator upstream of the EGR. Is this
> the correct configuration? My Vacuum diagragm (chiltons) does not
> show the Regulator but the Jeep Dealer says its fine. hmmm...
>
> Any ideas what could be causing this problem? I sure could used your
> help with this one.
>
> One other aggrevation, the Fuel Gage at 1/8th tank still has about 6
> gallons in it. Any way to adjust the gage in the dash?
>
> Thanks in advance...
>
> Mark
>
> PS: First time on the list.. Thanks guys (and gals), it's a great
> help!!!

Dave

Did you check the Coolant Temperature Sensor?
Are you sure your heated 02 sensor is getting it's 12volts and ground? This
is what it sounds like to me, or maybe it is not working.
I think the dealer is still doing recalls on these 02s.
I found out about that after finding a stash of them for mine or for sale.
:-(

I think that valve for the EGR is called a transducer. I had to clean the
carbon out of mine to get it to vent properly. It would cause the EGR Valve
to stay open and the engine would try to stall.
--
later,
dave
88 XJ 4.0 auto
82 Wag Ltd. 360 auto (to be retired!) anyone interested, whole or parts?
88 FSJ-GW 360 auto (GRAND 88)
Chicago


"CADman" <marcad2000@dslextreme.com> wrote in message
news:edacf47c.0401141957.1d3043b4@posting.google.c om...
> Here's my problem:
>
> I am bringing an old '89 Cherokee Pioneer 4.0L Automatic back to life
> while I rebuild my '87 Laredo 4.0L engine (got about 250,000 mile on
> it before it died). The '89 Pioneer was very clean inside and body
> straight, but the engine compartment was a horrible dirty mess.
>
> The problem is that, when I cold start, it runs fine (about 1200 rpm),
> then after about 46-60 seconds, rpm's drop badly to near stall (200
> rmp's or so) and runs rough. After it warms up, runs fine, smooth
> acceleration and has plenty of power AND just passed California Smog
> Test.
>
> Also, after a good run when warm, if I stop and shut down engine for
> 10-15 minutes or so and restart, it runs super rough (like on half the
> cylinders) until warm and reving the engine again.
>
> Here's what I've done:
>
> Thoroughly cleaned all connectors (TPS, IAC, CPS, O2 Sensor, Relays)
> and anything I could see and get my hands on.
>
> Thoroughly cleaned Throttle Body, IAC and IAC Port, Idle Air Port, and
> re-installed TBS with new gasket.
>
> Tightened exhaust/manifold bolts. They were a bit loose.
>
> Replaced MAP sensor with new part.
>
> Have tried two different used but cleaned IAC's. Same result.
>
> Compression is 140-150 cold on all cylinders.
>
> Set TPS to spec.
>
> New Distributor Cap, Wires, Plugs.
>
> Brakes and Booster seem OK (though the fluid was, still is, mocka
> brown. Full flush is next on the list of to do's). Though when in
> neutral, pumping the breaks causes about a 300 rpm increase. Is that
> normal? hmmm...
>
> O2 sensor test reads 6 ohm. Dead center on spec.
>
> EGR valve appears to be working OK. By the way, the 89 has a smaller
> EGR than my 87 and it has a Regulator upstream of the EGR. Is this
> the correct configuration? My Vacuum diagragm (chiltons) does not
> show the Regulator but the Jeep Dealer says its fine. hmmm...
>
> Any ideas what could be causing this problem? I sure could used your
> help with this one.
>
> One other aggrevation, the Fuel Gage at 1/8th tank still has about 6
> gallons in it. Any way to adjust the gage in the dash?
>
> Thanks in advance...
>
> Mark
>
> PS: First time on the list.. Thanks guys (and gals), it's a great
> help!!!

Jeepster

If the EGR is plugged then no exhaust is sent to the carb.... this of
course is not as per design but wouldn't cause his problem of stalling
on a cold start.... are you saying the EGR was plugged but still had a
clear flow path from exhaust to carb?

Again correct me guys if wrong here.... trying to learn.

After I cleaned my plugged EGR I could stall my YJ by forcing the EGR
open by pressing on the diaphram and opening the valve, prior to
cleaning it of course had no effect on the engine.

On Thu, 15 Jan 2004 05:30:20 GMT, "Dave"
<NO_vwdoc1_SPAM_@hotmail.com_PLEASE> wrote:

>Did you check the Coolant Temperature Sensor?
>Are you sure your heated 02 sensor is getting it's 12volts and ground? This
>is what it sounds like to me, or maybe it is not working.
>I think the dealer is still doing recalls on these 02s.
>I found out about that after finding a stash of them for mine or for sale.
>:-(
>
>I think that valve for the EGR is called a transducer. I had to clean the
>carbon out of mine to get it to vent properly. It would cause the EGR Valve
>to stay open and the engine would try to stall.

Jeepster

If the EGR is plugged then no exhaust is sent to the carb.... this of
course is not as per design but wouldn't cause his problem of stalling
on a cold start.... are you saying the EGR was plugged but still had a
clear flow path from exhaust to carb?

Again correct me guys if wrong here.... trying to learn.

After I cleaned my plugged EGR I could stall my YJ by forcing the EGR
open by pressing on the diaphram and opening the valve, prior to
cleaning it of course had no effect on the engine.

On Thu, 15 Jan 2004 05:30:20 GMT, "Dave"
<NO_vwdoc1_SPAM_@hotmail.com_PLEASE> wrote:

>Did you check the Coolant Temperature Sensor?
>Are you sure your heated 02 sensor is getting it's 12volts and ground? This
>is what it sounds like to me, or maybe it is not working.
>I think the dealer is still doing recalls on these 02s.
>I found out about that after finding a stash of them for mine or for sale.
>:-(
>
>I think that valve for the EGR is called a transducer. I had to clean the
>carbon out of mine to get it to vent properly. It would cause the EGR Valve
>to stay open and the engine would try to stall.

Jeepster

If the EGR is plugged then no exhaust is sent to the carb.... this of
course is not as per design but wouldn't cause his problem of stalling
on a cold start.... are you saying the EGR was plugged but still had a
clear flow path from exhaust to carb?

Again correct me guys if wrong here.... trying to learn.

After I cleaned my plugged EGR I could stall my YJ by forcing the EGR
open by pressing on the diaphram and opening the valve, prior to
cleaning it of course had no effect on the engine.

On Thu, 15 Jan 2004 05:30:20 GMT, "Dave"
<NO_vwdoc1_SPAM_@hotmail.com_PLEASE> wrote:

>Did you check the Coolant Temperature Sensor?
>Are you sure your heated 02 sensor is getting it's 12volts and ground? This
>is what it sounds like to me, or maybe it is not working.
>I think the dealer is still doing recalls on these 02s.
>I found out about that after finding a stash of them for mine or for sale.
>:-(
>
>I think that valve for the EGR is called a transducer. I had to clean the
>carbon out of mine to get it to vent properly. It would cause the EGR Valve
>to stay open and the engine would try to stall.

Will Honea

Sounds like the O2 sensor making it run rich but 30-45 seconds is a
bit too soon for that to be the root problem. I think that vacuum
leak in the brake booster may be the real culprit. I don't know if
the computer reads anything from the heater on the O2 sensor, but
that's another possibility. I fought cold idle problems with an 88 MJ
4.0 for months before I finally got everything working right - seemed
like everything I did helped a little but the problem didn't go
completely away until I changed the O2 sensor.

On Thu, 15 Jan 2004 03:57:49 UTC marcad2000@dslextreme.com (CADman)
wrote:

> Here's my problem:
>
> I am bringing an old '89 Cherokee Pioneer 4.0L Automatic back to life
> while I rebuild my '87 Laredo 4.0L engine (got about 250,000 mile on
> it before it died). The '89 Pioneer was very clean inside and body
> straight, but the engine compartment was a horrible dirty mess.
>
> The problem is that, when I cold start, it runs fine (about 1200 rpm),
> then after about 46-60 seconds, rpm's drop badly to near stall (200
> rmp's or so) and runs rough. After it warms up, runs fine, smooth
> acceleration and has plenty of power AND just passed California Smog
> Test.
>
> Also, after a good run when warm, if I stop and shut down engine for
> 10-15 minutes or so and restart, it runs super rough (like on half the
> cylinders) until warm and reving the engine again.
>
> Here's what I've done:
>
> Thoroughly cleaned all connectors (TPS, IAC, CPS, O2 Sensor, Relays)
> and anything I could see and get my hands on.
>
> Thoroughly cleaned Throttle Body, IAC and IAC Port, Idle Air Port, and
> re-installed TBS with new gasket.
>
> Tightened exhaust/manifold bolts. They were a bit loose.
>
> Replaced MAP sensor with new part.
>
> Have tried two different used but cleaned IAC's. Same result.
>
> Compression is 140-150 cold on all cylinders.
>
> Set TPS to spec.
>
> New Distributor Cap, Wires, Plugs.
>
> Brakes and Booster seem OK (though the fluid was, still is, mocka
> brown. Full flush is next on the list of to do's). Though when in
> neutral, pumping the breaks causes about a 300 rpm increase. Is that
> normal? hmmm...
>
> O2 sensor test reads 6 ohm. Dead center on spec.
>
> EGR valve appears to be working OK. By the way, the 89 has a smaller
> EGR than my 87 and it has a Regulator upstream of the EGR. Is this
> the correct configuration? My Vacuum diagragm (chiltons) does not
> show the Regulator but the Jeep Dealer says its fine. hmmm...
>
> Any ideas what could be causing this problem? I sure could used your
> help with this one.
>
> One other aggrevation, the Fuel Gage at 1/8th tank still has about 6
> gallons in it. Any way to adjust the gage in the dash?
>
> Thanks in advance...
>
> Mark
>
> PS: First time on the list.. Thanks guys (and gals), it's a great
> help!!!


--
Will Honea <whonea@codenet.net>

Will Honea

Sounds like the O2 sensor making it run rich but 30-45 seconds is a
bit too soon for that to be the root problem. I think that vacuum
leak in the brake booster may be the real culprit. I don't know if
the computer reads anything from the heater on the O2 sensor, but
that's another possibility. I fought cold idle problems with an 88 MJ
4.0 for months before I finally got everything working right - seemed
like everything I did helped a little but the problem didn't go
completely away until I changed the O2 sensor.

On Thu, 15 Jan 2004 03:57:49 UTC marcad2000@dslextreme.com (CADman)
wrote:

> Here's my problem:
>
> I am bringing an old '89 Cherokee Pioneer 4.0L Automatic back to life
> while I rebuild my '87 Laredo 4.0L engine (got about 250,000 mile on
> it before it died). The '89 Pioneer was very clean inside and body
> straight, but the engine compartment was a horrible dirty mess.
>
> The problem is that, when I cold start, it runs fine (about 1200 rpm),
> then after about 46-60 seconds, rpm's drop badly to near stall (200
> rmp's or so) and runs rough. After it warms up, runs fine, smooth
> acceleration and has plenty of power AND just passed California Smog
> Test.
>
> Also, after a good run when warm, if I stop and shut down engine for
> 10-15 minutes or so and restart, it runs super rough (like on half the
> cylinders) until warm and reving the engine again.
>
> Here's what I've done:
>
> Thoroughly cleaned all connectors (TPS, IAC, CPS, O2 Sensor, Relays)
> and anything I could see and get my hands on.
>
> Thoroughly cleaned Throttle Body, IAC and IAC Port, Idle Air Port, and
> re-installed TBS with new gasket.
>
> Tightened exhaust/manifold bolts. They were a bit loose.
>
> Replaced MAP sensor with new part.
>
> Have tried two different used but cleaned IAC's. Same result.
>
> Compression is 140-150 cold on all cylinders.
>
> Set TPS to spec.
>
> New Distributor Cap, Wires, Plugs.
>
> Brakes and Booster seem OK (though the fluid was, still is, mocka
> brown. Full flush is next on the list of to do's). Though when in
> neutral, pumping the breaks causes about a 300 rpm increase. Is that
> normal? hmmm...
>
> O2 sensor test reads 6 ohm. Dead center on spec.
>
> EGR valve appears to be working OK. By the way, the 89 has a smaller
> EGR than my 87 and it has a Regulator upstream of the EGR. Is this
> the correct configuration? My Vacuum diagragm (chiltons) does not
> show the Regulator but the Jeep Dealer says its fine. hmmm...
>
> Any ideas what could be causing this problem? I sure could used your
> help with this one.
>
> One other aggrevation, the Fuel Gage at 1/8th tank still has about 6
> gallons in it. Any way to adjust the gage in the dash?
>
> Thanks in advance...
>
> Mark
>
> PS: First time on the list.. Thanks guys (and gals), it's a great
> help!!!


--
Will Honea <whonea@codenet.net>

Will Honea

Sounds like the O2 sensor making it run rich but 30-45 seconds is a
bit too soon for that to be the root problem. I think that vacuum
leak in the brake booster may be the real culprit. I don't know if
the computer reads anything from the heater on the O2 sensor, but
that's another possibility. I fought cold idle problems with an 88 MJ
4.0 for months before I finally got everything working right - seemed
like everything I did helped a little but the problem didn't go
completely away until I changed the O2 sensor.

On Thu, 15 Jan 2004 03:57:49 UTC marcad2000@dslextreme.com (CADman)
wrote:

> Here's my problem:
>
> I am bringing an old '89 Cherokee Pioneer 4.0L Automatic back to life
> while I rebuild my '87 Laredo 4.0L engine (got about 250,000 mile on
> it before it died). The '89 Pioneer was very clean inside and body
> straight, but the engine compartment was a horrible dirty mess.
>
> The problem is that, when I cold start, it runs fine (about 1200 rpm),
> then after about 46-60 seconds, rpm's drop badly to near stall (200
> rmp's or so) and runs rough. After it warms up, runs fine, smooth
> acceleration and has plenty of power AND just passed California Smog
> Test.
>
> Also, after a good run when warm, if I stop and shut down engine for
> 10-15 minutes or so and restart, it runs super rough (like on half the
> cylinders) until warm and reving the engine again.
>
> Here's what I've done:
>
> Thoroughly cleaned all connectors (TPS, IAC, CPS, O2 Sensor, Relays)
> and anything I could see and get my hands on.
>
> Thoroughly cleaned Throttle Body, IAC and IAC Port, Idle Air Port, and
> re-installed TBS with new gasket.
>
> Tightened exhaust/manifold bolts. They were a bit loose.
>
> Replaced MAP sensor with new part.
>
> Have tried two different used but cleaned IAC's. Same result.
>
> Compression is 140-150 cold on all cylinders.
>
> Set TPS to spec.
>
> New Distributor Cap, Wires, Plugs.
>
> Brakes and Booster seem OK (though the fluid was, still is, mocka
> brown. Full flush is next on the list of to do's). Though when in
> neutral, pumping the breaks causes about a 300 rpm increase. Is that
> normal? hmmm...
>
> O2 sensor test reads 6 ohm. Dead center on spec.
>
> EGR valve appears to be working OK. By the way, the 89 has a smaller
> EGR than my 87 and it has a Regulator upstream of the EGR. Is this
> the correct configuration? My Vacuum diagragm (chiltons) does not
> show the Regulator but the Jeep Dealer says its fine. hmmm...
>
> Any ideas what could be causing this problem? I sure could used your
> help with this one.
>
> One other aggrevation, the Fuel Gage at 1/8th tank still has about 6
> gallons in it. Any way to adjust the gage in the dash?
>
> Thanks in advance...
>
> Mark
>
> PS: First time on the list.. Thanks guys (and gals), it's a great
> help!!!


--
Will Honea <whonea@codenet.net>