Help ! Super high idle

[BeatMj]

Hello I have a 90 comanche with the 4.0 and my idle is crazy high! I can't seem to find any vaccum leaks though, could this have anything to with the t.p.s or I.a.c. vaulve, any help would be greatly appriciated thanks....

[BeatMj]

I should mention that at first the idle is normal and doesnt seem to jump up untill I put a load on it (like putting it in gear and driving down the road) then it won't come back down. :fs1: Very frustrating....ugh

[MancheKid86]

oxygen sensor :thumbsup:

[BeatMj]

K ill check it out, I'm pretty sure there is a crack in the manifold next to the O2 sensor also

[500 MJ]

Clean your Throttle Body and see what that does for you, won't cost you but a can of carb cleaner and a couple hours of your time. Renix setups like clean TBs. I like to take them right off of the manifold and take them apart, use a brass brush to scrub the aluminum. While you have the throttle body apart, take a look at the idle air control valve and see what shape it is in...

 

Renix systems are actually very easy to cope with as long as you have a way to test the sensors. Here is a link to the FSM, it will tell how to test everything.

 

viewtopic.php?f=9&t=12517

 

As far as the manifold crack goes, that has never been the cause of issues with engines I've worked on. They crack and run weird, look into things and you can still trace the problem to something else, fix it and they run fine with the cracks. The cause of the cracks are most likely your motor mounts. Replace them before you mess with welding or replacing the exhaust manifold.

 

I drove my '88 for about a year on a cracked manifold, ran just fine the whole time even though it was a little bit louder than normal.

[1987Comanche]

Every time my TPS starts going bad my idle jumps way up. I went through 3 JY ones before I bit the bullet and scored a new one off E-bay.

[BeatMj]

Thanks for all the help guys, last night I pulled off the the I.a.c and cleaned it as well as the hole it goes into , seemed to fix my problem so far! Thanks again :)