[Intense-Dakota]

**** UPDATED - PLEASE READ FOLLUP POST'S ****


2004 WJ w/ 4.0L and 4x4. I have replaced, plugs, IAC, TPS, Crank Position Sensor, removed and completely cleaned throttle body (with sensors out). I have done an oil change, checked motor mounts and trans mount (they seem to be ok).

It runs rough (not to the violently shaking, but rough enough to get a message while sitting still) in Park, Neutral and all drive gears while sitting still (except for the first few second when I start up cold when the idle is still around 800-900 and then it drops to normal (around 550 rpm's). I just recently had it almost stall a few times when stopping at a light (RPM's did not seem to drop when it started to stumble). It will idle rough almost like rotational type of shimmy (hard to explain, but it will run rought for a second, then smooth for a second, then rough for a second and so on). It does not seem to be effected when the rpm's are any higher then idle. The tac always stays steady and does not fluctuate with the idle at all. Reseting the computer after changing IAC fixed the stalling for about 3 days. I reset the computer today when changing the CKP Sensor, and its not stalling, but the idle still seems to rough. The only things I have not checked or changed yet are the following:

Upstream O2 sensors
Downstream O2 sensors
Map sensor
Coolant temp sensor
IAT sensor
Fuel Filter/Regulator
Injectors
Coil Pack
Computer

I would rather not keep replacing parts with no change (except resetting the computer. I do have a warranty on it, but I have a $100 deductible so I am currently just replacing all the parts that would run less then $100. I have already had it in the shop 2 times, and they say (the famous I realy should'nt be a mechanic saying of) "We ran the diagnostics through the computer and it said everything was fine", so I really don't want to take it back again. I do have a vacum gauge, but not sure if that would help diagnose it or not (I use it to tune my dart, never on a fuel injected vehicle).

BTW- There is no check engine light, and I have pulled the codes 3 times with nothing showing (using the key trick 2 times, and AutoZone pulled once).

If anyone has any insight into this at all, even if one of the "havent changed parts" fixed your idle issue , please, please, please, please let me know.

[MEinSoCal]

i would look into replacing the fuel filter first, especially if you're the type that likes to let the gas tank run almost empty before refilling. next i'd consider taking the injectors out and having them balanced and flowed, if the fuel filter didn't do the trick

[Intense-Dakota]

do you have a quesstimate on how much the injectors would be to get them cleaned?

[newfieZJ]

how`s the exhaust sound , I mean is IT smooth or rough sounding ? I ask because , not knowing the mileage , and considering you`ve replaced lots , could it be as simple as a motor mount ? ?


EDIT , sorry , missed it being mentioned

[MEinSoCal]

Originally Posted by Intense-Dakota

do you have a quesstimate on how much the injectors would be to get them cleaned?

when i called around before it was like $20-25 per injector. not only do they clean but they also check the spray pattern on the injector and to be sure it flows what its rated at.

[Intense-Dakota]

I can hear the tone of the exhaust change slighly when it gets rough and if I hold my hand near the exhaust tip, I can feel a lighter pulse also. I have thought about the mounts, but they look ok (no rips or dry rotted rubber). My Jeep has about 47k miles on it. I have never had injectors tested before, what type of places do that? The stealer-ship?

[UTChavok]

I use Lucas fuel stabilizer regularly and run very smooth. Im not saying an additive with solve your problem but for $5-10 its worth a shot to go to autozone and pick this up and try it.

[XJeremy]

I would connect a scan tool and have a look at your long term fuel trim and
see if that is overly lean or rich, it really shouldn't be too much more than plus or minus 5%, maybe that would help you decide where to go next.

the pulsing in the exhaust suggests a misfire, IIRC wj's have individual coils..I don't know if its common but maybe you have one going out?

[Intense-Dakota]

New problem!!! Today when I went to start the jeep on lunch, it clicked (like the battery was dead) one time, the Trip and overhead milage reset to 0, but the radio stations are still there, and then started. Then once running, the dash voltmeter was doing some super strange things as seen in the linked video. I tried giving it gas to bring the idle up, but the idle speed made absolutely no difference in the voltage readings.

www.mopar4life.com/pics/MOV00012.mpg

Please help if you can.
Thanks,

BTW, its still running rough after changing the plugs, but no more stalls so far.

[mendelmax]

I see no mention about Mopar CCC. Have you tried it? My friend did it on his 93 4.0 few days ago and what a difference! And of course no trouble codes were present. It just worked like sh*t

[Intense-Dakota]

First off "Mopar CCC"??


Ok, more testing -

Battery w/ jeep off - 12.2-12.8v
Battery During Start - Lowest 5.4v Highest 11.6v
Running with accessories off 13.94v
Running with lights, AC at full and Radio 11.98-12.82v

However, even those these (except for starting) ar all pretty consistant, the volmeter on the dash is still moving quite a bit (not as much or as fast as in the video) but the volt meter hooked to the battery is not moving at all.

[mendelmax]

First off "Mopar CCC"??

It cleans combustion chamber from carbon deposits, so I guess it may help some. The part number is 04318001AB. It's like $10 or something, so I guess it's worth to try it. Won't charm.

The voltage numbers under load are quite low though. But I don't think they are bad enough to cause this sort of problem.

[kentman]

Alternator and/or battery? Any aftermarket wiring (e.g., amps, etc.)?

Also, for $35 you can install a new injector. I would much rather go with new rather than cleaned old injector for a similar price. If injectors were your problem, you would probably get a misfire code.

[Intense-Dakota]

Yesterday, picked up a new battery and installed it.
Today, the voltage is still acting crazy (see video link above if you havent)
So, I went to autozone and had them test the alernator while it was in the Jeep. Below are the readings at 2000 rpms.

peak voltage: 13.46
peak amps: 88.6
(They said that was good - that was with no lights on, just the radio on but turned down and the AC on low)

I have checked all battery cables and all the grounds I can find. I have also determined that the voltage seems to go up a bit once stopped, but after sitting for about 30-45 seconds, it starts to come down again and starts moving around again. It also seems that the Jeeps idle seems to be rougher when the idle drops a bits or starts moving around.

[vosevichs]

Getting back to your rough idle. Did you put platinum plugs in? If so remove them and go back to a regular plug.