gkeller81

Hi all, I have a 94 ZJ with the 4.0L engine and 87k miles and was hoping for some help with a problem or two. I have done so much research over the past few weeks I think I have convinced myself the problem could be caused by just about anything to do with the engine.

When the engine is cold it acts like it doesn't want to start, however it has never actually not started, just takes a few extra turns when cold. Also when it first starts when cold it acts like it wants to stall until I get it in reverse and give it some gas. If it has been driven within the last hour or so it will start right up and not want to stall.

The second issue seems opposite from the first. The warmer the engine gets the rougher it runs at idle, like when at a red light. When driving it seems fine. About a week ago it idled rough when stopped to the point it seemed like it may stall out and the CEL would come on after 15 mins or so. Pulled codes and got 51, which was fuel too lean, so I took it in and they replaced the plugs, dist. cap, and cleaned the throttle body. I cleaned the IAC myself. The idle seemed a bit better for a few days, but today after running some errands the Jeep stalled after cranking it up. I cranked it again and gave it some gas and it seemed to run fine once I got it on the road driving.

It also has a slight overheating issue when its hot out and I'm doing alot of stop and go driving (I'm in FL and it's been rainy alot lately and on those days its fine). Once in awhile when the temp guage gets to 210 (dead middle, where it's stayed pretty much all 3 years I've had it) it will suddenly drop 20-30 degrees, which I don't recall seeing happen before the overheating started. The shop found nothing wrong in regards to that issue, so I was going to replace the thermo in the next day or two to see what happens with that. The fan seems to work fine and was actually replaced about 2 weeks ago.

Lastly it has a small oil leak to where if I drive long enough for the car to get hot when I park I will have a 3-4" dried spot of oil the next morning. It doesn't leak at all if it isn't hot and when it does it drips down on the plate between the engine and tranny like it's the Rear Main Seal, but that problem I'm not as concerned about since I think its unrelated to the rough idle issue and should be straightforward to fix.

I'm not terribly mechanically inclined, but was thinking about replacing the fuel filter for the idle issue. Any other ideas for my problems for things I may be able to handle myself? I'm not too keen on paying a mechanic to throw parts at the problem for a car that's 17 years old. Thanks in advance for any help!

Zj heep

Try replacing fuel filter and fuel pressure regulator. Hope that helps.