fast idle

my 89 wagoneer ltd with a 4.0 L idles at 1100 in gear , out of gear it is at 1200 1250 rpm . does anyone else have this problem ? it has a new tps and has 260,000 kms 130,000 miles for you americans it runs strong but the fuel economy sucks .help

I have a similar problem ...

I would be grateful for any advice also...

Don't know if this could be a factor or not. My idle is pretty low, but haven't had any issues. Was having a problem with high idle etc and the car always wanting to crawl forward. Turns out the linkage where it pivots to pull the throttle cable was really stiff and stuck a bit. Lubed it up and haven't had the problem since. Not sure if this is a factor for you, but worth a look see. Haven't had a problem since.

As for mileage, I'm by no means an expert, but with my 4.0, we replaced all the spark plugs, fluids, ran higher octane gas for one full tank, new oil filter. I got approx 400km+ per tank, and in washington state passed emissions with flying colours. I also wonder if the mileage is related to the high idls as well. Just a thought.

ooh my 88' 4.0 has had the revving motor on and off for 8 months or so due to various things- the first fix I did was unplug (and blame) a brand new tps (that was bought very expensively in northern BC!) and that killed the fast idle (and fuel economy) a month ago I made a new front bumper and I had to move the vacuum canister for the cruise and dash controls and ended up cracking the PLASTIC!#%$ vacuum lines and cruise and vent control switches went bye bye ANYWAY I made my way through the vacuum system and luckily found the vacuum hose going to the MAP? sensor (the hose that goes from the little 3 plug vacuum tree to the green plugged sensor on the firewall) was cracked and when it would shake the right way with the engine idling it would cause a mild sustained 1200rpm rev up (how many is that in the metric system? so anyway get rid of ALL THE PLASTIC VACUUM HOSES or at least keep tabs on them. also I have an intake manifold gasket leak but that is a whole nother deal and has been duly factored into all my other rev up calculations
GOOD LUCK

Thanks man... rocks...

will be sure and replace anything under the hood that looks vac related...I have a pretty abused little xj here...

but there is tons of life in her still

thanks to the good folks here!

I have an 89 Cherokee 4.0l automatic and it has the same problem. When the engine is cold it idles around 800rpm but when it's warmed up it revs around 1450rpm. I put a new TPS and Coolant temp sensor on it with no change. I checked the vacuum lines and the throttle linkage. Could it be the Idle Air Control Motor? Or would it do it all the time?

Thanks

I have had the same problem,but also found out that if I disconnect the plug that goes to the TPS,wait bout 30 secs then plug it back in idle goes back to normal....go figger

So did you ever figure out what the problem was?

If the tps isn't adjusted properly it might do that, also the idle air control valve can be sticking or have a bad connection. When you shut the engine off it adjusts itself for the next start up. Another thing you might want to check is the egr valve which could be partially clogged or stuck open and the computer may be trying to compensate for that. Let me Know if you solve it. Lumpy

it has a new tps , i have to check all the vaccume lines , the linkage was tight before i bought it but i lubed it up good , i have to check out the iac and i was thinking it might be somthing to do with the air conditioning . agrrr this one is going to piss me off i know it ...

Just another thought, you could have bad connections at the those clunky connectors near the throttle body or the one on the firewall if it has that one.
As for the IAC, I take mine out every once in a while and clean it w/ carb cleaner spray. Check out this link it might be helpful. http://autotech.deanza.fhda.edu/drive8.htm

One guy suggested that I fully seat the IAC then unplug it. Then adjust the do not adjust screw for the throttle stop to 600 RPM on a warm motor. Then readjust the TPS to 12-14%, then if needed, readjust everything again and again until it stabilizes. Then reconnect the IAC and see what happens. Gonna try it, when I have a free afternoon and it stops raining. I´m gonna keep track of what I mess with (number of turns and voltage values) so I can get it back to where it is now.
Jneary suggested screwing out the lead cap covered screw in the TB and backing it out until it was flush, then fixing it (glue) with a dab of silicon. The orifice for the idle air adjusting screw, is plugged up, on my TB. Maybe just cleaning it out will help some.
Right now mine occasionally revs to 2000 at start up, on a warm motor, idles between 600 and 850 depending on the motor temp.
It all seems to change some when I disconnect the battery for awhile, but eventually returns after a day or so.

problem fixed, ok here is what i did and i hope it helps some of you out . first off i am lucky enough to have a parts truck on hand so i could swap parts around to see what was what . i swapped the throttle bodies . i took out the iac and cleaned the whole throttle body and the iac. when i put everything back, i put a new o-ring on the iac and tightend it up nicely. my theory was there was some sort of leak in the throttle body . im not sure if it was the old throttle body or the o-ring, but i recomend cleaning everything really good and getting a new o ring on there .it idles perfectly now woo hoo!!!!!... good luck to all hope it works for you