'98 Wrangler rough idle / power loss

[jef1f76]

I have a '98 Wrangler that has had rough idle/power loss issues. I was losing power to the point of having no power during acceleration. After replacing the o2 sensor and TPS sensor it got to where the Jeep ran fine after warming up about halfway. Up until that point it would barely idle enough to stay running but once it hit the halfway to warm point on the temp gauge it instantly would run fine and continue to do so until it cooled off again. Last night I used some throttle body cleaner on the TB and no the Jeep is idling high, close to 2k RPM. On the bright side, it isn't idling low and doesn't almost die at stop signs! Should I just replace the IAC? Sounds like maybe it is having issues and I'm finally narrowing in on it being the problem...

 

[TJ4Jim]

Welcome to the forum. What brand TPS did you install, our Jeeps do not like aftermarket sensors as they typically cause issues. The Idle air control can be cleaned in place with throttle body cleaner. Check out post #4 in the link.

https://wranglertjforum.com/threads/jeep-idling-like-crap.37973/#post-629572

 

[jef1f76]

it was a generic TPS from AutoZone. it definitely helped, just didn't totally fix the issue.

I cleaned the IAC in place as described in that post (actually saw a post from him about the same thing only with a little more detail in another thread). after the cleaning i was able to drive right at start up with the engine still cold which i haven't been able to do for a while now. only issue was the high idle

 

[The shuggs]

I've been having a similar problem. The initial code I got was for my TPS, but that code went away when I replaced it with a Mopar TPS. But the problem persisted, and gave a new code for my CMPS/CKPS. Replacing those didn't make a difference. I'm currently testing my clockspring. A faulty clockspring is known to mess with the TPS. The TPS, CMPS, and CKPS all share the same splice with the clockspring (S133 on our 98s).

Last night I removed the plastic shroud around the steering column, and unplugged the flat white connector from the back of the clockspring (there's a yellow connector next to it, that's for the airbag). This evening she'll be all cooled down, especially with the rain up here. I'll try starting her up to see if it makes a difference.

 

[TJ4Jim]

it was a generic TPS from AutoZone. it definitely helped, just didn't totally fix the issue.

I cleaned the IAC in place as described in that post (actually saw a post from him about the same thing only with a little more detail in another thread). after the cleaning i was able to drive right at start up with the engine still cold which i haven't been able to do for a while now. only issue was the high idle

Ok, the high idle is typically caused by a large vacuum leak so get in there and check the hoses connected to the intake manifold near the TB. Especially the vacuum line to the brake booster. Also, do yourself a favor and get a Mopar TPS..

 

[Jerry Bransford]

What brand of O2 sensor did you install? NTK? NGK? Bosch? Store brand?

 

[jef1f76]

it was a Duralast O2 sensor. the jeep has high miles so was just trying to see if i could get a quick fix to get even more miles out of it without putting much into it

 

[Jerry Bransford]

it was a Duralast O2 sensor. the jeep has high miles so was just trying to see if i could get a quick fix to get even more miles out of it without putting much into it

X1 it has to be an NTK or NGK sensor. X2 never run store brand sensors anywhere, and Duralast is the worst store brand of them all.

 

[jef1f76]

Ok, totally understand that. That being the case, are the symptoms the Jeep is experiencing a result of a cheap sensor or is the high idle something else?

 

[TJ4Jim]

Ok, totally understand that. That being the case, are the symptoms the Jeep is experiencing a result of a cheap sensor or is the high idle something else?

Both, get the sensors swapped out and check for vacuum leaks as I mentioned.

 

[jef1f76]

at the moment the only issue is intermittent rough idle during warm up. once it is warm (or about halfway to warm) it runs great, smoother than it has in years. would a vacuum leak act that way - only cause issues when the engine is cold?

 

[TJ4Jim]

at the moment the only issue is intermittent rough idle during warm up. once it is warm (or about halfway to warm) it runs great, smoother than it has in years. would a vacuum leak act that way - only cause issues when the engine is cold?

Typically no but it could very well be an intake/exhaust manifold leak at the head and that can close up as the engine warms. Just for giggles and shitz see if any of the manifold hardware is loose.

 

[jef1f76]

no obvious vacuum leaks. when i come to a stop and it is idling high i can tap the accelerator and it will drop to normal operating levels (750RPM). is that typically the IAC or TPS sticking? after i cleaned the IAC is when the problem switched to the high idle so logically you would assume IAC, correct?

 

[TJ4Jim]

no obvious vacuum leaks. when i come to a stop and it is idling high i can tap the accelerator and it will drop to normal operating levels (750RPM). is that typically the IAC or TPS sticking? after i cleaned the IAC is when the problem switched to the high idle so logically you would assume IAC, correct?

At this point you may want to consider removing the TB and pulling out the IAC for a manual cleaning, usually a tamper proof torx bit is required and they are available at Harbor Freight. There have also been issues (not common but it happens) with worn butterfly shaft seals leaking additional air causing idle issues. I went into my IAC recess and seat in the TB with a plumbers fitting brush and it came out sparkling.

 

[jef1f76]

I actually did that first before cleaning with throttle body cleaner directly into the TB. it helped some and going directly into the TB helped even more, just gave me the high idle

 

[Jerry Bransford]

At this point you may want to consider removing the TB and pulling out the IAC for a manual cleaning, usually a tamper proof torx bit is required and they are available at Harbor Freight. There have also been issues (not common but it happens) with worn butterfly shaft seals leaking additional air causing idle issues. I went into my IAC recess and seat in the TB with a plumbers fitting brush and it came out sparkling.

The IAC and its orifice in the TB it fits into can be thoroughly cleaned without removing it. All it takes is running the engine at IDLE rpms and spraying throttle body cleaner into the TB while the engine is idling. At idle rpms the IAC will pull the cleaner in through itself and through the orifice too. You just can't raise the rpms up off idle or the IAC will be bypassed and it'd never see any of the cleaner.

 

[TJ4Jim]

The IAC and its orifice in the TB it fits into can be thoroughly cleaned without removing it. All it takes is running the engine at IDLE rpms and spraying throttle body cleaner into the TB while the engine is idling. At idle rpms the IAC will pull the cleaner in through itself and through the orifice too. You just can't raise the rpms up off idle or the IAC will be bypassed and it'd never see any of the cleaner.

I agree 100% at this point he should get the Duralast crap off so there is a proper baseline. My thought was if all else fails pull the thing apart. I remember a few other threads somewhere that the shaft bearing on the butterfly was overly worn and one of the symptoms was tapping the throttle to relieve it temporarily.

 

[jef1f76]

The IAC and its orifice in the TB it fits into can be thoroughly cleaned without removing it. All it takes is running the engine at IDLE rpms and spraying throttle body cleaner into the TB while the engine is idling. At idle rpms the IAC will pull the cleaner in through itself and through the orifice too. You just can't raise the rpms up off idle or the IAC will be bypassed and it'd never see any of the cleaner.

I did that as well

 

[jef1f76]

revisiting this, still haven't been able to clear up the issue. the problem is actually getting worse now. other things have also popped up such as all of the gauges in the cluster stay flat when i start up the Jeep and will kick on after i wait for a bit. that problem is intermittent. could it possibly be ECM related??

 

[jef1f76]

aaaannnnnddddd.....it's dead. drove it last night and when i went to leave to go home and it wouldn't start. turn the key, dash lights up and heard a small hum but wouldn't turn over or start. no click. tried to jump start but no change. just sits there. seems electrical to me which, again, makes me wonder about the ECM/PCM??