cold engine misfire- 4.0
09-11-2009, 08:11 AM
#35
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Year: 1996
Model: Cherokee
Engine: 4.0
been reading...did a TPS test
its supposed to be .26v at idle, and 4.49v at WOT according to what ive found...
i tested mine and at idle is about .9v and at WOT its about 3.5v but it swings correctly in between the values...would this be what is causing my problems?
its supposed to be .26v at idle, and 4.49v at WOT according to what ive found...
i tested mine and at idle is about .9v and at WOT its about 3.5v but it swings correctly in between the values...would this be what is causing my problems?
09-11-2009, 09:28 AM
#36
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Year: 1996
Model: Cherokee
Engine: 4.0
more info I posted on another forum looking for help...gives you some background
Started out of the blue...
started as a CPS-fixed it, 3 days later it happened again (wire touched header, melted thru and shorted but I didnt see this) Wouldn't start so I paid a guy to scan and fix it. Almost $300 later for a new CPS and the cam sensor int he dist. I had it running again.
Another week goes by, it starts cutting out, slowly gets worse until it won't run at all. It starts and immediately stalls unless you give it gas. Eventually determined the dist. gear was worn, teeth were worn down to almost nothing, throwing the timing out-no idle but will run "ok" in the upper rpms. New distributor and its runs like a champ. In the process of finding the issue I put on a new TPS, CPS again, cap, rotor.
I get 1,000 miles on it and its cutting out again, wont idle...check the dist and its worn again. OK, so now I know the cam gear is causing it, need a new cam or new motor. Got a motor cheaper than I could replace the cam, so I swap motors. now I have this misfire condition, not sure what is causing it, thinking a lack of fuel/lean condition casuing the backfire thru the intake. It sometimes happens cold, sometimes hot. I cant pattern it to just one set of conditions. Its random.
Last night I did a TPS test, volts were .9 at idle, 3.5 at WOT...dunno if thats too far out of spec or not...it was a autozone TPS not mopar. The reason I suspect this is I had cleaned the intake manifold with Brake cleaner to remove some oil/carbon build-up in the runners and it was running back thru the TB, which i then sprayed the TB to clean it out. Maybe I got it wet and ruined it. Thinking I may swap this again to see if it clears up.
Also I had suspected O2 sensor...but the problem happens whether the O2 sensor is plugged in or not.
Total list of new parts-
CPS
camshaft sensor in dist
TPS
cap
rotor
plugs
ECU from another 96 XJ
Started out of the blue...
started as a CPS-fixed it, 3 days later it happened again (wire touched header, melted thru and shorted but I didnt see this) Wouldn't start so I paid a guy to scan and fix it. Almost $300 later for a new CPS and the cam sensor int he dist. I had it running again.
Another week goes by, it starts cutting out, slowly gets worse until it won't run at all. It starts and immediately stalls unless you give it gas. Eventually determined the dist. gear was worn, teeth were worn down to almost nothing, throwing the timing out-no idle but will run "ok" in the upper rpms. New distributor and its runs like a champ. In the process of finding the issue I put on a new TPS, CPS again, cap, rotor.
I get 1,000 miles on it and its cutting out again, wont idle...check the dist and its worn again. OK, so now I know the cam gear is causing it, need a new cam or new motor. Got a motor cheaper than I could replace the cam, so I swap motors. now I have this misfire condition, not sure what is causing it, thinking a lack of fuel/lean condition casuing the backfire thru the intake. It sometimes happens cold, sometimes hot. I cant pattern it to just one set of conditions. Its random.
Last night I did a TPS test, volts were .9 at idle, 3.5 at WOT...dunno if thats too far out of spec or not...it was a autozone TPS not mopar. The reason I suspect this is I had cleaned the intake manifold with Brake cleaner to remove some oil/carbon build-up in the runners and it was running back thru the TB, which i then sprayed the TB to clean it out. Maybe I got it wet and ruined it. Thinking I may swap this again to see if it clears up.
Also I had suspected O2 sensor...but the problem happens whether the O2 sensor is plugged in or not.
Total list of new parts-
CPS
camshaft sensor in dist
TPS
cap
rotor
plugs
ECU from another 96 XJ
09-11-2009, 01:04 PM
#37
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Year: 1996
Model: Cherokee
Engine: 4.0
how much does TPS have to do with transmission? i developed a new symptom...when its acting up, i was trying limp it home on some backroads, it would hardly do 15mph. as i would try to take off, light throttle it would carry on and stumble and slowly move along, if i tried to give it alot of throttle pedal it would start to rev and felt like it was in nuetral until i let off then it would go back into gear.
09-12-2009, 10:35 PM
#38
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well swapped TPS and a put a new IAC in it...no dice
leaves me with a MAP sensor but at $100 ill be JY hunting for one.
gonna do a new coil and wires next then find the MAP...
if that dont fix it, it gets the torch to be cut up and parted out
leaves me with a MAP sensor but at $100 ill be JY hunting for one.
gonna do a new coil and wires next then find the MAP...
if that dont fix it, it gets the torch to be cut up and parted out
09-14-2009, 07:48 AM
#41
Timing.
Since the distributor cannot be advanced or retarded manually, the only other possible causes (assuming proper indexing) are as follows.
Improper valve train timing (including bad/stripped distributor gear or cam gear)
Bad Cam or Crank Sensor
Bad PCM
Since the distributor cannot be advanced or retarded manually, the only other possible causes (assuming proper indexing) are as follows.
Improper valve train timing (including bad/stripped distributor gear or cam gear)
Bad Cam or Crank Sensor
Bad PCM
09-14-2009, 09:32 AM
#42
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Year: 1996
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I pulled and re-indexed the dist yesterday just to make sure (also dist gear is good as i dealt with that before, reason for changing the motor)- no change
ECM has been changed with another one from a 96- no change
problem seems to be getting worse- does it when cold or warm, no way to really limit it to one condition.
the problem can be deceiving, each time i try to eliminate another item or try something, the engine may start and run beautifully as i go cruising around 5-8 miles making sure i both cruise at steady throttle and hammer down a bit to take it through all rpm range. at times i can make it through the entire drive and just before i make it back home, there is a long red light, it will start to stumble as im sitting there idling, and from that point its 10mph limping back to the house. after a few minutes of terrible running in the driveway it will clear up again for awhile. maybe a bit of heatsoak while sitting still with little air movement. this isnt ALL the time tho, sometimes it will act up immediately on a cold motor also.
i also put a used O2 sensor in (not a new one, dont want to waste more $$) with no change.
i did the ohms test on my crank sensor, and it passed, but maybe i need to do the ohms test again after everything is good and hot and immediately after i get the problem to start again.
BTW FrankZ i appreciate all your help with this, sooner or later I have to find out what it is.
ECM has been changed with another one from a 96- no change
problem seems to be getting worse- does it when cold or warm, no way to really limit it to one condition.
the problem can be deceiving, each time i try to eliminate another item or try something, the engine may start and run beautifully as i go cruising around 5-8 miles making sure i both cruise at steady throttle and hammer down a bit to take it through all rpm range. at times i can make it through the entire drive and just before i make it back home, there is a long red light, it will start to stumble as im sitting there idling, and from that point its 10mph limping back to the house. after a few minutes of terrible running in the driveway it will clear up again for awhile. maybe a bit of heatsoak while sitting still with little air movement. this isnt ALL the time tho, sometimes it will act up immediately on a cold motor also.
i also put a used O2 sensor in (not a new one, dont want to waste more $$) with no change.
i did the ohms test on my crank sensor, and it passed, but maybe i need to do the ohms test again after everything is good and hot and immediately after i get the problem to start again.
BTW FrankZ i appreciate all your help with this, sooner or later I have to find out what it is.
09-14-2009, 11:09 AM
#44
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as soon as i get a chance to get the adapter i will do a compression test, and i am also going to do another fuel pressure test just to be 100% sure its not the pump.
its frustrating that one minute its making plenty of power and will 1 wheel peel my 32's on blacktop, the next its running rough and wont do but 15mph.
its frustrating that one minute its making plenty of power and will 1 wheel peel my 32's on blacktop, the next its running rough and wont do but 15mph.