hobhayward

I know there are a whole boatload of these intermittent power loss threads but it seems like there can be a number of causes.

I've had the cherokee for a couple months now (1999 xj, 130k, auto tranny), round 2k miles. It sat for about a month before I bought it and 15 miles into owning it I got two codes p0340 and p0138 - camshaft position sensor and rear o2 sensor. Replaced the o2 sensor, cleared the codes got it inspected all seemed well. Camshaft position sensor code has not come back (checked today even just to be sure even though the cel is off).

The problem: Occasionally after having run for a while and then sitting off for about 10 minutes, I'll start it up and pull away, above around 2k rpm it starts to struggle and rpm will drop, giving it gas seems to make it run more roughly, and with nearly full throttle it will suddenly jump up to full power, then stutter again once or twice and seem to be fine after that for the rest of the drive. If don't floor it and I take my foot off the gas and give it gas gently a few times it will seem to resume normal function. It also seems to randomly lose a tiny bit of power on the highway every now and again.

The two most popular fixes I've seen are front o2 and crankshaft position sensor. I'm going to replace the front o2 tomorrow as I believe it is probably the original and it can't hurt to have a new one. Now going back to the CAMshaft position sensor, does it seem plausible that that could be source of the problem? I've read that they do not fail very often, but it is strange that I had the code for it. The CRANKshaft position sensor is known to be more likely to go. The last thing I would investigate would be the TPS, as those also tend to fail. Is there anything I'm missing that could save a lot of headache and money on sensors?

One last thing.. The engine seems to make plenty of ticking noise (like valves or lifters) I assumed it was normal but figured I would mention it anyways.

Thanks for any and all ideas!

freegdr

Check wiring also for contact to metal surfaces while down there .

hobhayward

Could a bad CAMshaft position sensor be the cause of these symptoms?

hobhayward

Last night the problem developed further.

Power steering feels weak, and it seems like you need to give it more pedal to get the same power as before, but otherwise it seems to be running just fine. Idles around 800 rpm, idle fluctuates a little and seems a hair rough, but not to bad.

Picking up a tb gasket after work today going to clean all of that. Tested the TPS at lunch and I didn't observe anything out of the ordinary (voltage range was .8-3.8v,though the spec says it should be .5-4.0?)

Still no engine codes, o2 sensor is is in the mail (rockauto is half of napa's price, even after shipping).

Does this trigger any other ideas? I'm more confused now than before..

wildbill1

My '99 will do something similar. If I park it and restart it after it sits for a little while, it will stumble a few times before taking off and running fine again. I think it's an injector heat soaking. It never has gotten any worse, so I haven't done anythng about it.

hobhayward

Sounds reasonable, I figured it was something heat related and it happened so infrequently at first that I didn't bother worrying about it. As to injector heat soak though, I had only heard about the 00-01 engines having issues.

It has gotten much hotter here recently (MA), been upper 80's lower 90's all week, and I was thinking that the problem worsening was due to that, but now its not just stumbling a little bit..

Any other theories on why the heat would make a difference?

CCKen

TPS spec at idle is: voltge should be greater than .26 volts but less than .95 volts, and at wide open throttle it must be less than 4.40 volts.

Generally the upstream O2S will cause stumble under initial acceleration. A good cleaning of the TB, including the IAC pintle and its orifice is in order as well.

I suggest if you are considering a new TPS, get an OEM TPS from the dealer. The aftermarket TPS's generally do not meet voltage spec, or simply do not last long.

Hope you got an NTK O2S from Rockauto.

hobhayward

Thoroughly cleaned the TB including the IAC and its orifice. Seems like its running a tad smoother but it still idles the same as before.

The o2 sensor is indeed NTK and coming from rockauto, wish I had ordered my bank 2 sensor from them when I replaced it, Napa charges twice as much for the same part, and that was the only reason I didn't replace bank 1 at the same time.

I think I'll hold off on the TPS for now, I monitored it via obd2 and it behaved normally while I was driving. Crankshaft position sensor seems worth replacing just because they seem to be such a common issue, I think that's my next move unless someone has another suggestion.

What's confusing me the most now is the power steering, could engine issues result in power steering becoming stiffer? Could be a coincidence of course lol, it is a jeep after all.