1989 Jeep limited high idle speed

[bgreed]

Hi new here but this looks like the place to find answers. My Jeep has crazy high idle speed in park it wants to idle at nearly 2500rpm. I have done a search but not found any articles. Where do I start to look to solve this problem? It has the 4.0L and is fuel injected. Thanks for the help
Gregg

[cantab27]

hi Gregg and welcome to the site....does ya jeep shift OK when driving,, may be tps....

[bgreed]

Shifts just fine. Whats TPS?

[4.3LXJ]

Throttle postion sensor

[bgreed]

Just figured that out:p I changed that today same problem continues. Put a new AIC in just a few months ago will check that and clean it. Anyother thoughts?

[4.3LXJ]

Check for vacuum leaks

[Brasscatz]

Also, check your throttle to see if it sticks. With it running, and under the hood, try to move the throttle down to see if that's your problem

[bgreed]

Checked for vacum leaks didn't find any. When you cold start it is revs up then settles down to where it should idle, then as it warms up the idle speed increases to where sitting at a stop light it's around 1200 rpm if I put it in park it res up to around 2k or higher. Throttle is not stuck I'm out of ideas. Any more thoughts??

[Jeepster19]

Sounds like you have a bad throttle cable.Remove the cable from the throttle body then operate the throttle by hand via the throttle body,revving the engine a time or two,it should return to idle.If not,try cleaning the throttle body to see if it helps,the throttle blade-shaft assembly should move freely without any hang-ups.Now to the cable you have disconnected.Move it back and forth to see if you have any binding,if you do replace the cable.Also go inside and make sure the pedal isn't hanging up on anything,carpet,floormat,etc.Let us know what you find out.:D

[bgreed]

OK checked all that and cleaned the throttle body no change. Anyother ideas?

[4.3LXJ]

My opinion is that you have a vacuum leak on the intake. Check the base of the throttle body. Sounds like that is where it is.

[Baddmove]

I have the same problem with my 87 cherokee.. so far i have replaced IAC,TPS,plugs, cap,rotor, mine still does it, going to put in new injectors this week, if that doesn't solve it i will have to take it to the stealership, i'm out of options here also..no one seems to know what is causing this...here the thread i started, you can see we have the same problem..
http://www.xjtalk.com/showthread.php?t=10999

[Jeepster19]

Stop by your local auto parts store and get a can of carburetor cleaner and spray around the throttle body,intake and all vacum lines.If there's a leak the carburetor spray will find it.:D

[bgreed]

Tried the trick with carb spray showed nothing. I removed the trottle body to clean it and used a gasket sealer to remount it along with the gasket so no leaks there.

Totally stumped

[BlueXJ]

Check the bolts holding the intake/exhaust on. They frequently back out and cause vacuum leaks. If no solution there then try a computer reset. Un hook both battery cables and then touch them together for 10-20 seconds. Then let everything set for 15 minutes then re-hook them up. Everything will be off for 8-15 starts then everything will settle back to normal. It takes a bit but you are re-training the ECU.

[bgreed]

You understand that mine is a 1989 wagoneer limited. Did they have computers then?

[4.3LXJ]

Yes they did

[BlueXJ]

The actual computer module should be behind the cardboard box of your glovebox. Most were mounted there.

[bgreed]

Well I tried the battery disconnect idea and no luck there either. So I am pretty much stumped at this point. No Vacum leaks that I can find even using carb cleaner, bolts on throttle body are tight as I removed it when I cleaned it and used a gasket sealer when I reassembled it. Have replaced the TPS, replaced the IAC, trottle is not sticking. Soooooo I Dunno??:confused:

[oderdene]

if not checked, check fuel pressure regulator. When idling, disconnect vacuum hose, which connects manifold and pressure regulator.

here is good read for Renix 4.0 http://www.lunghd.com/Tech_Articles/Fuel_System/Fuel_Diagnostics.htm

and a PDF www.lunghd.com/Downloads_and_Links/Jeep_Renix_Fuel_Injection_manual.pdf

[BlueXJ]

You never said whether or not you checked the bolts holding the intake to the head. They frequently back out and cause vacuum leaks.

[bgreed]

Your right I didn't mention about checking the throttle body bolts since I mentioned that I had removed the throttle body when I cleaned it. Even after putting it back the engine idle was high.