Hey guys i got a problem with my 93 xj with 4.0l
today i decided to take off my throtle body toaday and clean it. it had some oil in it and oil also on the IAC valve. So i cleaned them up with carb cleaner and spayed alot into the IAC.
put it all back together, and it idles at 2k rpm.

drove it around a bit and nothing changed.

figured i had killed the IAC by sraying it so i bought a new one and put it in. I also put a new gasket on the TB since the old one rippped.

Now it idles at 3K RPMS!!!!

took it apart again, and gently pulled out the shaft on the New IAC.

tried again. now its back to 2k rpms.

drove it around with no change.

i went and bought a brand new TPS and put it on. unplugged the batt, put it back and no change. still runs at 2k rpm.

i cheaked for vac and intake leaks by spraying carb cleaner everywere. none were found and its still at 2k rpm.

PLEASE HELP ME!!!! i dont know what else to do guys.
thanks

 

stupid question but.. Did you make sure the throttle plate is closed all the way?

 

I don't have any answers but I am interested to see what people think because I too have checked everything you listed and have the same problem. once it warms up a little bit it goes up to 2k rpm.

the strange thing for me is that if I am off road riding some trails or something similar It will typically idle at 1k rpm or a little higher.

 

when you get a new IAC it has the "set period" it will idle high for about 5 minutes before it sets itself (or rather the computer) and idles where it should. you may need a new one..... see if you can exchange it for a new one, put it in(making sure the o-ring is on it) an then start it let it idle and set itself to normal

 

well it is closed for the most part. it is just baaaaarly open. just a sliver. the adjustment screw is set to keep it like that. that is how it was set before i cleaned the TB and it ran fine then. also the scew is rusty and looks like it has been set like this for awhile. so that leads me to belive that this is how it should be set.

 

thats what il probly do. il exchange it and say that it was defective (it may or may not be, but i want another fresh start).
so should i just let it idle at 2k for 5 mins right now?

 

well i ruled out the IAC. i covered the little inlet in the TB that goes to the IAC and the idle didnt change. i once again cheacked for vac leaks and found non.
this is getting scary.

 

Check your cables and for any vac leaks. If you have a propane torch, don't light it just turn the gas on and run it around the area and it will idle higher if there is a leak anywhere.

 

alright so this is going to sound weird however coming home today i take my foot off of the gas to engine brake and slow down a little bit and i speed up! i am like what the heck! put it in neutral and brake to slow down and my engine still stayed at 2500rpms... did this anytime i was in neutral.... and now it is still high idling i am going to disconnect the battery take my TB apart and clean. Either way now i am in your same boat. so i will keep you posted with mine (not to thread jack, just 2 heads[or engines] is better than one right?) I am now tuned to this thread as well

 

no problem at all. hopefully we can learn from eachother. Right now i have no idea what else to try. i just stand in the garage looking at it and feel like throwing up.

 

are you sure your throttle plate is closing all the way? it very much sounds to me like your throttle plate is sticking.
or, this is just a waaay distant possibility, but your manifold gasket might have started leaking. when you had the tb off, did you happen to brace yourself on the intake manifold to move around under the hood?

 

did you make sure that you put your o ring back on??? if it to one side of the divider to much its sucking to much air= higher idle.. or did you break the screws so its sucking air from around the parimeter of it?

 

so just went and started my jeep, high idle for about a minute or 2 then settled back down to normal. I pulled the intake hose and looked at it and the butterfly was perfectly closed with no wiggle room. it always seems to die down for me. just takes along time to come off of its high idle trip

 

but i disconnected the battery terminals, and am going to let it sit over night. ill report tomorrow

 

I've been trying to track down a 1200 rpm idle for a while now and read tons of threads on the subject. Done the throttle body cleaning, IAC cleaning, check TPS, IAT, CTS, MAP and leak check with propane with no results. The only odd data point for me was that during the winter cold ambient temperature (eg 20 deg F or less) it idled closer to normal maybe 800 rpms. I hate the "throw parts at it" approach and can't help but think that there is a specific answer so please keep us posted.
Thanks
Bruce