Rough running/idling Cherokee
06-15-2012, 03:30 PM
#16
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Getting something similar. I do have the P0138 which I believe is the front O2 sensor. I also had a very worn distributor. Up until today the Jeep ran 'OK' sometimes the MIL lit sometimes not, definitely ran better with it off but in general the Jeep was drivable.
Today I changed out the worn dizzy and now I have the MIL on constantly an revving anything over 1200rpm caused a sever misfire with backfiring and worse
I checked the firing order, and have gone through the install of the dizzy from step one, TDC, with oil spigot lined up and dizzy slotted in correctly.
Any advice?
Today I changed out the worn dizzy and now I have the MIL on constantly an revving anything over 1200rpm caused a sever misfire with backfiring and worse
I checked the firing order, and have gone through the install of the dizzy from step one, TDC, with oil spigot lined up and dizzy slotted in correctly.
Any advice?
12-14-2012, 12:31 AM
#17
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Year: 1999
Model: Cherokee
Engine: 4.0 straight six
Ok well its been a little while however the problem still remains!! I have a 99 cherokee classic 4.0 v6 4x4 with automatic trans. I have recently replaced the motor and tranns. with another 99 4.0 and automatic transmission with fewer miles.
BEFORE and AFTER I replaced the motor my jeep would run sporadically from time to time with no warning; one moment i'm cruising down the road and the next my jeep losses power and starts almost jolting. Its almost like there is a loose connection or something, i could almost compare it to a flickering light bulb scenario. Any how I went through this most recent motor with new spark plugs, plug wires, distributor cap & rotor, map sensor, and tps sensor, just must my luck this did not fix the problem and it still runs like ****.
It will also idle down when in park and act as if it might stall but it never does. Most recently i took it to a friend where we tested the compression; #4 was slighty weak but the rest were good, we also got a weak reading on one of the O2 sensors but it seemed to be functioning ok.
Any ideas what might solve this problem??
BEFORE and AFTER I replaced the motor my jeep would run sporadically from time to time with no warning; one moment i'm cruising down the road and the next my jeep losses power and starts almost jolting. Its almost like there is a loose connection or something, i could almost compare it to a flickering light bulb scenario. Any how I went through this most recent motor with new spark plugs, plug wires, distributor cap & rotor, map sensor, and tps sensor, just must my luck this did not fix the problem and it still runs like ****.
It will also idle down when in park and act as if it might stall but it never does. Most recently i took it to a friend where we tested the compression; #4 was slighty weak but the rest were good, we also got a weak reading on one of the O2 sensors but it seemed to be functioning ok.
Any ideas what might solve this problem??
12-14-2012, 06:04 PM
#19
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Check the enginf to chassis ground wire. Its a big flat ribbon wire that goes from the farthest rear bolt on the valve cover to the firewall behind the engine, cant miss it. I had the exact same symptoms your having. Mine was caked with oil and gunk. Take it off, clean all contact points, and the nuts holding it. Then wipe the wire down good. Ill bet this fixes all your problems. If not, another place to go next is your throttle body. Take off the throttle body and check the idle air controller. Be very careful to not bend or break the fragile inner core of it. The and is beveled and fits into the throttle body tightly. If it gets carboned up it will cause the engine to stall at idle. While your at it, remove and clean the map sensor, and clean out the throttle body itself. Good luck, hope this helps. I have a 2000 cherokee with the 4.0 straight 6. 150k+ miles and still purrs like a kitten!
12-15-2012, 04:05 PM
#20
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Year: 1999
Model: Cherokee
Engine: 4.0 straight six
I cleaned the ground that goes from the valve cover to the fire wall ( That would be the ribbon type one), the throttle body is clean, and IAC valve and map sensor are both new all of which are great points and I thought would solve the problem unfortunately it did not fix the problem.
Could someone tell me about the ground to the PCM? I dont know what that is and didnt realize there was a ground there..this was a post that i received: "Did you clean all the grounds to the PCM? I think you will need to remove the air cleaner housing to get good access."
Also I checked the fuel pressure and it was good; even when my jeep started to run like crap the fuel pressure was fine.
Here are my thoughts; could anyone tell me if this would cause my jeep to run erratically like i have explained above?
1.) Faulty Computer
2.) Faulty O2 sensor (wouldn't it run like crap all the time if this was the case?)
3.) Bad Ground (even though I have checked all the grounds that I know of)
I just don't understand how my Cherokee runs so dam good and then all of a sudden it will run like absolute **** for no more than 1 minute and go right back to running great WTF!!!!!!???
Also on top of this I was told the other day that my four ways come on when turning left only. I have a weird suspicion that it only will do it when I apply my breaks and turn left because I have checked my left blinkers when in park and they work fine.
Could someone tell me about the ground to the PCM? I dont know what that is and didnt realize there was a ground there..this was a post that i received: "Did you clean all the grounds to the PCM? I think you will need to remove the air cleaner housing to get good access."
Also I checked the fuel pressure and it was good; even when my jeep started to run like crap the fuel pressure was fine.
Here are my thoughts; could anyone tell me if this would cause my jeep to run erratically like i have explained above?
1.) Faulty Computer
2.) Faulty O2 sensor (wouldn't it run like crap all the time if this was the case?)
3.) Bad Ground (even though I have checked all the grounds that I know of)
I just don't understand how my Cherokee runs so dam good and then all of a sudden it will run like absolute **** for no more than 1 minute and go right back to running great WTF!!!!!!???
Also on top of this I was told the other day that my four ways come on when turning left only. I have a weird suspicion that it only will do it when I apply my breaks and turn left because I have checked my left blinkers when in park and they work fine.
12-16-2012, 03:37 AM
#21
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1.) Faulty Computer
Unlikely as your Jeep runs OK most of the time.
2.) Faulty O2 sensor (wouldn't it run like crap all the time if this was the case?)
A faulty upstream O2 will give you a rich or lean mixture. Its unlikely to be bad only some of the time.
3.) Bad Ground (even though I have checked all the grounds that I know of)
Pretty sure you have an electric problem. Do you live in a country area? Rodents do like wiring. You might need to check the whole loom for damage. Given your other electrical issues it would seem that this could be where the root cause will be. If your problem happen more in damp or rainy conditions its almost certainly damaged wiring.
The PCM supplies ground for the injectors and ignition.
Unlikely as your Jeep runs OK most of the time.
2.) Faulty O2 sensor (wouldn't it run like crap all the time if this was the case?)
A faulty upstream O2 will give you a rich or lean mixture. Its unlikely to be bad only some of the time.
3.) Bad Ground (even though I have checked all the grounds that I know of)
Pretty sure you have an electric problem. Do you live in a country area? Rodents do like wiring. You might need to check the whole loom for damage. Given your other electrical issues it would seem that this could be where the root cause will be. If your problem happen more in damp or rainy conditions its almost certainly damaged wiring.
The PCM supplies ground for the injectors and ignition.
12-16-2012, 10:38 AM
#22
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Year: 1999
Model: Cherokee
Engine: 4.0
Ok well its been a little while however the problem still remains!! I have a 99 cherokee classic 4.0 v6 4x4 with automatic trans. I have recently replaced the motor and tranns. with another 99 4.0 and automatic transmission with fewer miles.
BEFORE and AFTER I replaced the motor my jeep would run sporadically from time to time with no warning; one moment i'm cruising down the road and the next my jeep losses power and starts almost jolting. Its almost like there is a loose connection or something, i could almost compare it to a flickering light bulb scenario. Any how I went through this most recent motor with new spark plugs, plug wires, distributor cap & rotor, map sensor, and tps sensor, just must my luck this did not fix the problem and it still runs like ****.
It will also idle down when in park and act as if it might stall but it never does. Most recently i took it to a friend where we tested the compression; #4 was slighty weak but the rest were good, we also got a weak reading on one of the O2 sensors but it seemed to be functioning ok.
Any ideas what might solve this problem??
BEFORE and AFTER I replaced the motor my jeep would run sporadically from time to time with no warning; one moment i'm cruising down the road and the next my jeep losses power and starts almost jolting. Its almost like there is a loose connection or something, i could almost compare it to a flickering light bulb scenario. Any how I went through this most recent motor with new spark plugs, plug wires, distributor cap & rotor, map sensor, and tps sensor, just must my luck this did not fix the problem and it still runs like ****.
It will also idle down when in park and act as if it might stall but it never does. Most recently i took it to a friend where we tested the compression; #4 was slighty weak but the rest were good, we also got a weak reading on one of the O2 sensors but it seemed to be functioning ok.
Any ideas what might solve this problem??
One or more fuel injectors may be malfunctiong causing a lean mixture, or a rich mixture. Check the fuel injector wiring where it exits the back of box manifold just above the injectors. There have been reports of the wiring exiting the manifold being chaffed and grounding out there. If a PCM injector driver wire grounds out there it will cause the injector to stay open, dumping fuel in the manifold.
How old are your injectors BTW? A clogged injector will cause a lean mixture that the PCM sees through the upstream O2S. if the PCM sees a lean mixture it will try to compensate by increasing all the fuel injectors dwell (causing a rich mixture). It only takes one injector to cause this.
O2S:
You said "we also got a weak reading on one of the O2 sensors but it seemed to be functioning ok." What does this mean? Did your friend use a scanner to observe live O2S data with the engine running? Or did he use a voltmeter to make this determination? One must use a scanner to watch the O2S's in action. This will tell you a great deal about the health of the O2S's and what is happening in the O2S/PCM fuel injection system. This includes the action of the downstream O2s, which monitors the gases exiting the CAT. A blocked CAT will show up if the O2S's are monitored with a scanner.
CCV:
The OBDII 4.0 requires a calibrated vacuum leak. The CCV [valve] fitting at the rear of the rocker cover has a 'calibrated' orifice in it, about 1/8" in diameter. It is plumbed to the intake manifold where it gets its vacuum. If the orifice gets plugged the vacuum to the rocker cover will be reduced and the calibrated leak ceases to exist, causing the engine RPM (at idle) to fall off/be low. This can be proven by removing the CCV rubber hose coupling at the intake manifold and start the engine. The RPM will be excessively high due to the large vacuum leak. Now slowly cover the intake manifold vacuum fitting on the intake with your finger. As you decrease the size of the fitting opening you'll see the RPM come down. If you cover the fitting opening the engine will quit.
You cannot see the metering orifice in the CCV, even with the valve cover removed. The only way to check it is to remove the CCV from the valve cover. If your replacement engine had a CCV installed on its valve cover this may not be an issue, but it's worth keeping in the back of your mind.
PCM Ground:
The PCM is externally grounded. The image below shows the location of the PCM ground point.
Suggestions:
1. Inspect the injector wiring,
2. Access and use a scanner to observe the O2S live data while your engine is running.
01-10-2013, 09:30 AM
#24
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Year: 1999
Model: Cherokee
Engine: 4.0 straight six
I inspected the wiring towards the back of the fuel injectors and it seemed to be ok. the TCM and PCM grounds were connected and appeared to be fine.
My mechanic was the one that brought up the 02 sensor and he used a scanner to check this. All he had told me was that the front 02 sensor seemed to act faulty very briefly but then straightened out. He also checked the compression on each cylinder he noted that cylinder 4 had lower compression than the others (he said it could be a bad valve or simply gunk thats built up on it).
As for the fuel injectors I do not know if they have ever been replaced.
My last comment would be that I drove my Cherokee for almost a week straight I would let it warm up in the morning and then head off to work and it ran great for almost a whole week and it only ran ****ty once or twice for a few seconds. I fired the old girl up the other day and it was right back to the same old thing rough idle and running very erratically at constant speeds of 30 or 40 mph. I just dont understand how it can run great for 3-4 days and then go back to running like **** again.
My mechanic was the one that brought up the 02 sensor and he used a scanner to check this. All he had told me was that the front 02 sensor seemed to act faulty very briefly but then straightened out. He also checked the compression on each cylinder he noted that cylinder 4 had lower compression than the others (he said it could be a bad valve or simply gunk thats built up on it).
As for the fuel injectors I do not know if they have ever been replaced.
My last comment would be that I drove my Cherokee for almost a week straight I would let it warm up in the morning and then head off to work and it ran great for almost a whole week and it only ran ****ty once or twice for a few seconds. I fired the old girl up the other day and it was right back to the same old thing rough idle and running very erratically at constant speeds of 30 or 40 mph. I just dont understand how it can run great for 3-4 days and then go back to running like **** again.
10-21-2013, 11:51 AM
#25
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Year: 1996
Model: Cherokee
Engine: 4.0
Check your downstream o2 (located on catalytic converter) sensor the same way you check the first. If it is damaged it will tell the PCM there's too little/much oxygen past the Cat.
If that doesn't help, your Catalytic converter may have restricted air flow. You can get a generic Cat. roughly the same size for half the price of OEM internet prices.
If the muffler or cat are stopped up completely, you'd be doing good to idle poorly. I once saw a guy back into a small hill and crimp his tail-pipe. The car instantly started the "woomp wooom lunge sputter".
Good luck!
If that doesn't help, your Catalytic converter may have restricted air flow. You can get a generic Cat. roughly the same size for half the price of OEM internet prices.
If the muffler or cat are stopped up completely, you'd be doing good to idle poorly. I once saw a guy back into a small hill and crimp his tail-pipe. The car instantly started the "woomp wooom lunge sputter".
Good luck!
12-14-2013, 11:23 AM
#27
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i just have one question for this thread. what did you do to make your jeep run right again? i read the starter thread, it sounds just like what my jeep is doing. i have put in enough $$ to buy a new car, & it is still doing the same thing. im getting super frusterated with this as it has been almost 2 months since it started happening. 
please help me out on figuring this out
please help me out on figuring this out
12-14-2013, 11:36 AM
#28
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Fuel Injectors:
One or more fuel injectors may be malfunctiong causing a lean mixture, or a rich mixture. Check the fuel injector wiring where it exits the back of box manifold just above the injectors. There have been reports of the wiring exiting the manifold being chaffed and grounding out there. If a PCM injector driver wire grounds out there it will cause the injector to stay open, dumping fuel in the manifold.
How old are your injectors BTW? A clogged injector will cause a lean mixture that the PCM sees through the upstream O2S. if the PCM sees a lean mixture it will try to compensate by increasing all the fuel injectors dwell (causing a rich mixture). It only takes one injector to cause this.
O2S:
You said "we also got a weak reading on one of the O2 sensors but it seemed to be functioning ok." What does this mean? Did your friend use a scanner to observe live O2S data with the engine running? Or did he use a voltmeter to make this determination? One must use a scanner to watch the O2S's in action. This will tell you a great deal about the health of the O2S's and what is happening in the O2S/PCM fuel injection system. This includes the action of the downstream O2s, which monitors the gases exiting the CAT. A blocked CAT will show up if the O2S's are monitored with a scanner.
CCV:
The OBDII 4.0 requires a calibrated vacuum leak. The CCV [valve] fitting at the rear of the rocker cover has a 'calibrated' orifice in it, about 1/8" in diameter. It is plumbed to the intake manifold where it gets its vacuum. If the orifice gets plugged the vacuum to the rocker cover will be reduced and the calibrated leak ceases to exist, causing the engine RPM (at idle) to fall off/be low. This can be proven by removing the CCV rubber hose coupling at the intake manifold and start the engine. The RPM will be excessively high due to the large vacuum leak. Now slowly cover the intake manifold vacuum fitting on the intake with your finger. As you decrease the size of the fitting opening you'll see the RPM come down. If you cover the fitting opening the engine will quit.
You cannot see the metering orifice in the CCV, even with the valve cover removed. The only way to check it is to remove the CCV from the valve cover. If your replacement engine had a CCV installed on its valve cover this may not be an issue, but it's worth keeping in the back of your mind.
PCM Ground:
The PCM is externally grounded. The image below shows the location of the PCM ground point.
Suggestions:
1. Inspect the injector wiring,
2. Access and use a scanner to observe the O2S live data while your engine is running.
One or more fuel injectors may be malfunctiong causing a lean mixture, or a rich mixture. Check the fuel injector wiring where it exits the back of box manifold just above the injectors. There have been reports of the wiring exiting the manifold being chaffed and grounding out there. If a PCM injector driver wire grounds out there it will cause the injector to stay open, dumping fuel in the manifold.
How old are your injectors BTW? A clogged injector will cause a lean mixture that the PCM sees through the upstream O2S. if the PCM sees a lean mixture it will try to compensate by increasing all the fuel injectors dwell (causing a rich mixture). It only takes one injector to cause this.
O2S:
You said "we also got a weak reading on one of the O2 sensors but it seemed to be functioning ok." What does this mean? Did your friend use a scanner to observe live O2S data with the engine running? Or did he use a voltmeter to make this determination? One must use a scanner to watch the O2S's in action. This will tell you a great deal about the health of the O2S's and what is happening in the O2S/PCM fuel injection system. This includes the action of the downstream O2s, which monitors the gases exiting the CAT. A blocked CAT will show up if the O2S's are monitored with a scanner.
CCV:
The OBDII 4.0 requires a calibrated vacuum leak. The CCV [valve] fitting at the rear of the rocker cover has a 'calibrated' orifice in it, about 1/8" in diameter. It is plumbed to the intake manifold where it gets its vacuum. If the orifice gets plugged the vacuum to the rocker cover will be reduced and the calibrated leak ceases to exist, causing the engine RPM (at idle) to fall off/be low. This can be proven by removing the CCV rubber hose coupling at the intake manifold and start the engine. The RPM will be excessively high due to the large vacuum leak. Now slowly cover the intake manifold vacuum fitting on the intake with your finger. As you decrease the size of the fitting opening you'll see the RPM come down. If you cover the fitting opening the engine will quit.
You cannot see the metering orifice in the CCV, even with the valve cover removed. The only way to check it is to remove the CCV from the valve cover. If your replacement engine had a CCV installed on its valve cover this may not be an issue, but it's worth keeping in the back of your mind.
PCM Ground:
The PCM is externally grounded. The image below shows the location of the PCM ground point.
Suggestions:
1. Inspect the injector wiring,
2. Access and use a scanner to observe the O2S live data while your engine is running.
12-15-2013, 06:42 PM
#30
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spark plug coil pack ok?
It may be a bad spark plug coil pack. Or, did you make sure all the little springs were secured onto the plugs? Make sure none fell out or werent snapped on when putting the pack back on? Check the wiring for the pack? I changed my plugs once and when test driving, ran great then all of a sudden started to run like hell lose power, jump and skip. Went home and checked, sure enough one of the springs fell out when I put the coil pack on. Snaped it onto the plug problem solved. Getting the coil pack back on just right is a bit of a challenge. Also, is the plug for the Idle Air Control ok? And even though it is a new IAC, is it working properly? Did you try turning the idle up just a hair? After the last time mine acted up, I simply turned the idle up a little problem solved. Hope you get it figured out bud!