anyone near Boulder-FoCo have a Compression/leakdown tester?

[BlacknBlue_XJ]

Got an injector and misfire code on cylinder 5 the other day. It was hot as hell outside and I stopped to pick up food, so I thought it might be heatsoak. I've had heatsoak before and it occurred immediately upon starting, but I was always able to push through it in 30 seconds or so. This time, it started at a traffic light leaving the parking lot after a smooth start. I was also under the impression that it's generally #3 that gets cooked.

Several minutes down the road it was still struggling and the CEL was blinking (active misfire, I think), and I pulled off into a parking lot. It struggled to idle and would stall if I revved it and let it drop. There was a strong smell of gas, but no visible leaks in the engine compartment or underneath. I let it cool for about 15 minutes and cleared the codes. It threw the codes again after a few minutes, but I was able to get back to work without any more stalls. Driving home at a relatively constant 50mph on farm roads, CEL/bad idle/misfire happened again at a stoplight, but ran perfect the next 15 minutes home (blinking stopped at some point). Cleared the codes and restarted at home and it idled fine for a few minutes with no codes.

Anyway, I'm going to test coil packs, plugs, and the injector, but I've read that bad compression can cause this as well. With a rattle coming from the motor that could be bearings or could be a flexplate, this might be worth checking.

I'm also open to ideas and suggestions. Anything else I should do or check?

It's a 2001, 225k, pretty much stock.

 

[BlacknBlue_XJ]

Dang, quiet in here...

 

[trippled]

A compression issue would usually not randomly clear up.

Honestly id just go buy a cheap one somewhere. There not bad to buy and then you have one for later.

 

[old_man]

You can borrow one from Autozone with a deposit. I have one but IIRC it doesn't like to fit down in the spark plug hole on a Renix head.

 

[md21722]

I'm pretty sure you can rent them for free at O'Reilly's or places like that.

There is a TSB for the random multiple cylinder misfire:

http://www.wjjeeps.com/tsb/tsb_wj_0900303.pdf

On my 2001 it could drive fine for hours, then getting stuck in traffic it would start acting up.

If that's in fact your problem, then you can try the decarbonizing process, and if that doesn't work, the head must come off. If the head has to come off, suggest replacing with a TUPY or CCH or whatever, since the 0331 are prone to crack as well.

 

[BlacknBlue_XJ]

Tom, thanks for the offer. I remember trying once last year and the store clerk had no idea what either was. It's a crap shoot with the person you get at the counter, so I'll call around to a few in Longmont to see if they have one. Did you get my PM about the u joint?

MD, I have come across that TSB. Did you always get random multiple cylinder misfire codes? I only get injector and misfire for 5. I'll try decarbonizing anyway. Couldn't hurt.

If I have to rebuild the head it'll probably be part of a whole build. I'm keeping an eye out for a builder motor to do on the side. Keeping my fingers crossed for a bad injector or coil pack.

 

[thejeepgod]

I have a builder motor (knocking) from a 00 if you have any interest in it. PM me.

 

[md21722]

MD, I have come across that TSB. Did you always get random multiple cylinder misfire codes? I only get injector and misfire for 5. I'll try decarbonizing anyway. Couldn't hurt.

The problem was highly intermittent for about 60,000 miles before it got worse. During this time I was living in Tennessee and going to up to an office in New Jersey monthly. The Jeep would drive fine until I was sitting in traffic in Maryland on I-95 then the CEL would start blinking. Once moving again it was like nothing was wrong. It did this for many trips. However, on the last trip, the next morning as I headed into the office it was stumbling so I took it to a local guy we knew for years. He found the issue within an hour and said low compression 50, 120, 105, 115, 100, 85 needs engine (looked up the old repair bill). I told him it doesn't use any oil the problem is in the head. He pulled the head, the valves were the problem. Multiple cylinders were throwing misfire codes and I had the multiple cylinder misfire code. I suspect this problem took out the mini-cat prematurely. I had a CEL for that came on at 100,000. The CEL burnt out at 260,000. It still passed Denver emissions when they put it on the treadmill. I finally changed the mini-cats last year at around 340,000 when I replaced the rear main seal. Since doing that, the dreaded summer time heat soak issue has all but gone away.

 

[BlacknBlue_XJ]

Thanks for the info, MD. Sounds pretty similar.

Jeepgod, thanks for the offer but I don't have the space or an engine hoist at the moment. Looking like this may be a project that starts next summer or winter. I'll post up in here when I'm ready to get going on it.