Rough intermittent idle and stall

I have gone through the threads here and am still scratching my head. I have a 1995 jeep cherokee xj with the IL 6 motor. Its runs great while driving down the road, but the problem is that while at idle it has an intermittent, slight, jittery idle. does not make a diff weather engine is warm or cold. It has also stalled on me twice in the last 235mi and thought that i had narrowed it down to the coil. replaced the coil and it has not stalled again but still having rough idle. one thing that i have noticed is that the aux fan kicks on randomly when it is still cold and running around 110 deg. not sure if this is normal, but now that i have the problem, I notice odd. The following is a list of the thing that I have already compleated.

1. New plugs within the last 1000 mi. (champion)
2. Brand new plug wires.
3. New IAC sensor and cleaned out the housing.
4. Sea Foam treatment in Fuel tank
5. Checked all vac lines.
6. New coil.
7. New ground and cleaned ground contact point.
8. New air filter.
9. Checked all fuses.
10. Checked fuel presure
11. New O2 Sensor 3500mi ago
12. Checked for vaccum leaks with a can of carb cleaner.

Any help with this issue would be great. thanks in advance.

excellent second post-- you covered most of the basics that are usually asked first!:thumbup:

I'd check first to make sure you're not running around with the HVAC set to defrost as this will cycle the AC and the cooling fan (can also give you varying idle speed and quality)

did you replace the dist cap and rotor with the plugs or wires?

does it start quickly after turning key, or is there a longer than usual crank time? The CPS can affect idle quality if it's on it's last leg (although usually doesn't last long after symptoms begin) and can increase crank time as well.

High Roller, I had a similar issue w/ my 88. Try your CPS on the bellhousing, over time they will demagnatise and get screwy. I also had this issue again when I installed my CPS and somehow my wire touched the manifold, melted the shielding and was grounding out on the manifold. Unfrotunately I do not think that there is a test for your CPS short of replacing it, with a renix there is a resistance you can take but yours is only one wire. If you look at the firewall near the Map sensor you will see the connector going down to the 11 o'clock position on the bellhousing. Its a PITA to change but I am pretty sure it'll be your issue.

Another question, when your aux fan is cycling (when the motor is still cold) what setting is your HVAC controller on?

The fan will cycle on any setting but OFF, HEAT, and VENT....

Any of the 3 A/C (Max, Norm, & Bi-level) settings will obviously cause the fan to cycle, but it will also cycle with defrost as the A/C is also used for that setting.

If your HVAC controller is set to OFF, Vent, or Heat and the motor is cold and the fan is still cycling, check or replace the coolant temp sensor which is threaded into the thermostat housing. This could also cause a rough idle as well as a general rough running of the motor I'd assume.

Although the crank positioning sensor (CPS) on the bellhousing, as mentioend by Stihl is alot more common to go bad and you'll hear it all of the time here on these forums!

Still having problems

see below

Shorty- I think that you were right about the HVAC and it being on defrost as far as the fan because it has been cold here in the mornings and nights so its been on almost every time i drive on low. I did not replace the dist cap and rotor with the plugs and wires, but i did take a look inside and there where no signs of carbon, oil, or tracking. I take a sec or two to start but i have noticed that in the last couple of the more recent times trying to start i had to release the key because it was almost as if the motor started to bind, but then after turning key immediately after it starts. CPS???

Stihl-i did inspect the wire for the CPS and found no problems or shorting. I have had a very slight oil leak in the rear main seal are. not enough to leave any spots on the driveway, but enough to cover the inspection plate for the flex plate. would a slight amount of oil fault the CPS?

Blaine B- I did replace the coolant temp sensor, but it made no improvements to the idle quality. I guess I am going to replace the CPS tomorrow and see if that fixes the issue. Everyone seems to be leaning towards that. It would explain the random stalls on two occasions i have had happen now. I thought that if the CPS was bad, once it dies on you, you would not be able to restart it.

I have also noticed a nice black lip stick ring around the opening of the tail pipe which is only about 2 weeks old. I'm thinking that this is caused from the SEA FOAM treatment I have been running through the tank this whole last week. Yes???

You did replace the coolant temp sensor in the thermostat housing, right? Not the one at the back of the head? The one on the head is for the gauge.

What about the cam sensor under the distributor cap? More than likely to be the crank positioning sensor on the bellhousing....however I had a no start situation back in 2006 and after replacing the crank positioning sensor on the bellhousing, it still would not start. Replaced the cam position sensor under the distributor cap (or sometimes they call it a STATOR) and it has been fine ever since. Alot of stores do not even list a cam sensor for the XJ, FYI.

I did replace the the sensor in the thermostat housing. Is the cam sensor located under the distributor on the engine block or under the distributor cap? I thought that was a pick up coil under the cap which i actually have not thought about looking at. Didn't think of that being a possibility. How much does a cam position sensor run? Is there a cam position sensor on a 1995 IL-6? I thought it was only on the V-6 motor?

Yes pickup coil, that is what I meant to say, under the distributor cap. However on the auto store computers they sometimes list it as stator/cam sensor/pickup coil, at least from my searching an experience.

When I bought mine it was about $40 to $50.

mine had a high idle only when it got warm. took it into a jeep shop and diagnosed a bad intake manifold gasket. idle was rough and could'nt idle worth $hit.

Hallo. I wonder ,was the Sea Foam treatment a good idea?
You renewed also the O2 sensor. Is it not damaged or is it the right one? :wave1:

so its pre OBDII. possibly fouled injectors or plugs with the sea foam...

Blaine- I will check out the pick up coil next after I replace the CPS.

Smittty- It runs and drives great and idles at about 700RPMs. the only thing weird is that it has stalled a couple times and has a weird shake/intermittent jitter at Idle. I also already checked the intake with some break cleaner and found nothing and I pulled all the plugs last night and replaced with new ones even thought the old ones looked fine. It is the OBDII and I thought that SEA FOAM was and injector cleaner anyway, not a fouler. I understand that it could break loose contamanants in the fuel take but the fuel filter should take care of that right which I did replace. I dose seem to have a tiny bit more throttle response since the cleaning, but still have the slight jitter in idle. I changed the fuel filter Yesterday after putting in new gas.

Wim Hoppenbrouwers- All of the problems existed prior to the sea foam treatment. Like i was telling Smittty, the plugs are brand new. installed last night with the gap dead on. as far as the injectors I'll keep that on the back burner for things to check when I'm done installing the new CPS and checking out the pick up coil.

Thanks for all the input guys. I'll keep you posted once the problem is finally resolved. I'm off to gather new parts.

I also will second Wim Hoppen.....too many letters to remember....

If you ran the Sea Foam treatment after the O2 Sensor replacement, you'll probably want to change it again. They are very sensitive to additives and contamination.

I've not heard of Sea Foam clogging injectors, as it's added into the intake stream and should only flow past the tip of the injector on it's way to the combustion chamber, but you may still have an injector leaking and causing your problem. Try a fuel pressure leakdown test after the CPS if the problems persist.

So now I have replaced the cap, rotor, and CPS and still no change. I checked the map sensor and seems to be working fine. Also disconnected the oxygen sensor wile at idle and did not make any difference. Does that mean it's bad?

I have also noticed that my catalitic converter is welded on backwards. It has been like that since i bought it and never had any problems. could that have any effect? I still need to change the o2 sensor and camshaft position sensor.

I must know. Did any of the stuff you tried work? I have the exact same problem. For me it started when I broke the passenger side motor mount and damaged the cap. I've replaced that and cleaned both the throttle body and IAC, checked the wiring, plug gap and plug wires. It's still doin' it though, and I don't want to get into it for a lot of time and parts.

none of it made a difference. thinking about pulling the injectors to in and have cleand by local shop. let me know if you have any luck. i've been banging my head trying to figure out the problem although it has not stalled since i replaced the coil, so that is one thing taken care of.

The O2 sensor worked for me. I have had a very similar problem before. Twice. The first time was a clogged fuel filter, which doesn't always show low fuel pressure until the demand goes up, ie. driving for a few feet. And the second time it was a bad ground in the wire harness right behind the oil pressure sensor. There are a number of wires grounded there and one was loose and very oily. I just cut the wire and crimped a new connector on and I haven't had that particular problem again (yet).