My XJ Idles high

My XJ idles high, i've replace the idle air control, i've flushed the radiator, i've been tryin all kinds of things, lubed the crap outa the throttle linkage, i dont know how to adjust the small but to make the idle lower, and i know there is something wrong with my vaccum canister can someone help please, this is driving me crazy i've been trying to figure it out for at least a month and im about ready to give up

oh yea 1990 XJ 4.0HO

THanks

AJ

Garst1323 said:

My XJ idles high, i've replace the idle air control, i've flushed the radiator, i've been tryin all kinds of things, lubed the crap outa the throttle linkage, i dont know how to adjust the small but to make the idle lower, and i know there is something wrong with my vaccum canister can someone help please, this is driving me crazy i've been trying to figure it out for at least a month and im about ready to give up

oh yea 1990 XJ 4.0HO

THanks

AJ

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TPS, latch relay causes some high idle issues as well as the ignition switch. With the later ECU thinks the starter is still turning and keeps IAC open. Does it only idle fast when re-started HOT? 90 HO? I guess that's not a Renix but it's similar except for the non-adjustable TPS.

haha Im not that good with the engine stuff yet, i might need you to interpret that a little better, tps means throttle positioning sensor? and is that right next to the IAC?

AJ

Yes, the TPS is next to the IAC. I would strongly reccomend checking your oxygen sensor if you have not done so already. It can cause the idle to stay high as well as other problems. Good Luck!!

How is it a 1990 H.O.? If you've swapped a H.O. into your 90 you might want mention that year. If it is a Renix there is an idle adjustment screw, but you will have to readjust the tps after you adjust the idle. How bad is it? I mean if its bad like 2500 you might have other problems. Take the TB off the vehicle and spray the crap out of it with carb cleaner(make sure its sensor safe)

I didnt know that there was a difference between the engines i thought all 4.0's were high output thats my mistake, the engine in my 90 is the stock engine

The single most common reason for a high idle is a vacuum leak. On your year model, check the hard line running to the vacuum cannister behind the front bumper. They tend to break right next to the battery.

I drive a 1990 4.0 engine. Every high idle episode on mine has been faulty TPS. I'm on my third since new. If you have an automatic transmission, you may also note a weirdness to the tranny shifting (odd timing) when the TPS is going out. Water kills TPS- if you clean your engine, keep all water away from the TPS for the Renix (up to 1990) sensors- not sure if it applies to the HO TPS. I'm with Old Man on this one: look for vacuum leaks, check the TPS, then go on to the other suggestions posted. Also, the TPS up to 1990 is adjustable, and needs to be in-spec to work. The procedure has been posted, try a search for TPS. I found that the dealer, on scope, could get a finer adjustment than I could with a multimeter. With high idle, people jump to the Idle Air Controller, and I believe that isn't usually the problem: check to see if it moves during the start-up sequence before replacing it.