99 Trooper won't idle

Joined: Nov 28, 2006 Posts: 2

I have a 99 trooper with an idle problem. Codes were being thrown for the rear O2 sensors and then for the MAF sensor. It would die at stop lights and sometimes even on the highway when I took my foot off the gas. Initially it was occasional and then got progressively worse. It has 100k so I went ahead and replaced O2 sensors. No help. I replaced the MAF, which SEEMED to help but the problem returned. I found that resetting the computer (which I did during the MAF replacement by disconnecting the battery for a while) fixed the problem for a day or two and then at some point I would try to start it and it would be unable to idle. Sooo I am thinking that the sensors themselves are fine, but reporting a problem in the mixture and trying with all their might to correct the problem but failing. I am thinking there is an air leak in the intake somewhere, most likely at the intake manifold gaskets, which are notorious for cracking on Rodeos, and I assume Troopers as well. (I have a 98 Rodeo that had this problem but the symptoms were never so bad that it wouldn't idle. Replacing the gaskets was a major @#$@!$ pain.)

Has anyone experienced (and conquered?) similar demons?
Anyone think I'm off base with the intake leak?

External Since: Oct 06, 2006 Posts: 8

> I have a 99 trooper with an idle problem. Codes were being thrown for
> the rear O2 sensors and then for the MAF sensor. It would die at stop
> lights and sometimes even on the highway when I took my foot off the
> gas. Initially it was occasional and then got progressively worse.
> It has 100k so I went ahead and replaced O2 sensors. No help. I
> replaced the MAF, which SEEMED to help but the problem returned. I
> found that resetting the computer (which I did during the MAF
> replacement by disconnecting the battery for a while) fixed the
> problem for a day or two and then at some point I would try to start
> it and it would be unable to idle. Sooo I am thinking that the
> sensors themselves are fine, but reporting a problem in the mixture
> and trying with all their might to correct the problem but failing. I
> am thinking there is an air leak in the intake somewhere, most likely
> at the intake manifold gaskets, which are notorious for cracking on
> Rodeos, and I assume Troopers as well. (I have a 98 Rodeo that had
> this problem but the symptoms were never so bad that it wouldn’t idle.
> Replacing the gaskets was a major @#$@!$ pain.)
>
> Has anyone experienced (and conquered?) similar demons?
> Anyone think I’m off base with the intake leak?

Intake manifold leak is likely - I've experienced it, and symptoms are
somewhat similar. It's simple to check by spraying some 'start gas' (or
any other combustible gas) on intake manifold gasket while engine is
idling - change in RPM will indicate a leak.

Another thing to check is idle air motor - these things get gunked up.
Relatively simple to take off & clean, maybe a 30min job in total.

Peter