Topic: New Problem with my jeep- slightly High idle issue

[countryboy15]

I have 91 YJ. It has the 4.0 throttle body and spacer. It also has a custom air intake. Well today(2/17/10) I start my jeep and immediately the idle goes to about 1500 Rpm. Then The idle dropped down gradually (over the time span of seconds) to 1000 rpms, and it will not go any lower nor higher in the rpm range while idling. I know one of the previous owners buried my jeep in mud by the dirt falling from under my dash, so I am letting you all know it has not been very well kept in its lifetime and giving yall a broader view as what just might be the problem. I would rather get this fixed pretty quick so it does eat away at my clutch as bad and my make me pay even more on my jeep. My lil' repair manual doesnt say anything say anything about idle issues and I am hoping the people(yall) can help me so I can save a lil' money to put somemore stuff on my jeep. So if you have any suggestions that might fix this, let me hear them. Thanks in advance for any help.

[sharpxmen]

I have 91 YJ. It has the 4.0 throttle body and spacer. It also has a custom air intake. Well today(2/17/10) I start my jeep and immediately the idle goes to about 1500 Rpm. Then The idle dropped down gradually (over the time span of seconds) to 1000 rpms, and it will not go any lower nor higher in the rpm range while idling. I know one of the previous owners buried my jeep in mud by the dirt falling from under my dash, so I am letting you all know it has not been very well kept in its lifetime and giving yall a broader view as what just might be the problem. I would rather get this fixed pretty quick so it does eat away at my clutch as bad and my make me pay even more on my jeep. My lil' repair manual doesnt say anything say anything about idle issues and I am hoping the people(yall) can help me so I can save a lil' money to put somemore stuff on my jeep. So if you have any suggestions that might fix this, let me hear them. Thanks in advance for any help.

do you have the 2.5L idle air control valve and housing installed on your 4.0t/b? what about the tps, is it off your 2.5L?

[TrailsLessTaken]

The idle adjustment screw on the TB may have been adjusted.  The cherokee I took mine off of was a pos and i think the previous owner had adjusted the screw to keep the rpm's up so it wouldnt die.  Mine had idled about 1200 and i lowered the set screw a couple turns and it sits about 900-1000 now I need to take it back off and mess with it some more

[countryboy15]

do you have the 2.5L idle air control valve and housing installed on your 4.0t/b? what about the tps, is it off your 2.5L?

The only thing that is different is the tps because I couldn't get it off due to the fact I didn't want to break the small torx bolts. It didn't do this after I installed the throttle body with the 4.0 tps. Would this be it?

The idle adjustment screw on the TB may have been adjusted.  The cherokee I took mine off of was a pos and i think the previous owner had adjusted the screw to keep the rpm's up so it wouldnt die.  Mine had idled about 1200 and i lowered the set screw a couple turns and it sits about 900-1000 now I need to take it back off and mess with it some more

Where is this located? I am interested because I might look into this as a cheap fix for now. I doubt it has ever been adjusted because the 4.0 L throttle body came off of my wrecked jeep with a 4.0 in it and it didn't have the problem of staying at 1000 rpm right after insalled the throttle body. But it is possible that I do have someone(who knows about motors) messing with my jeep since one of my wheels almost fell off the other day.

[sharpxmen]

The only thing that is different is the tps because I couldn't get it off due to the fact I didn't want to break the small torx bolts. It didn't do this after I installed the throttle body with the 4.0 tps. Would this be it?

Where is this located? I am interested because I might look into this as a cheap fix for now. I doubt it has ever been adjusted because the 4.0 L throttle body came off of my wrecked jeep with a 4.0 in it and it didn't have the problem of staying at 1000 rpm right after insalled the throttle body. But it is possible that I do have someone(who knows about motors) messing with my jeep since one of my wheels almost fell off the other day.

it is on the lever side of the butterfly shaft. it is an small allen screw, you might be able to access it if you have a spacer, but usually you need to take the t/b off to have access to it (from underneath where the gsasket goes on the t/b. you can adjust it but at some point you will end up with the butterfly resting on the inside fo the throttle body and if you leave it like that you will end up creating an edge in which your butterfly can get stuck - so best is to have it a little bit lifted off with that set screw so it doesn't touches the inside of the t/b.

[dwtaylorpdx]

The screw is an over travel stop not an adjustment for idle, you will eventually run out of travel.

the IAC valve on my YJ needs a good shot of carb cleaner about every other oil change...

Dave