Back during the summer I had a crate engine put it, and since then I have had issues with the idle. It usually is higher at stop around 1000rpm, and if I let my foot off of the brake and gas while driving it will pull itself along doing a good 20mph. Also when I shift into park or neutral, it will rev up to 1500 or even 2000.

I have checked for vacuum leaks and there doesnt seem to be any. I cleaned the TPS and just today ive replaced the IAC. It worked fine for the first two start ups after I swapped it out. After that it went back to the same old high idle. I am thinking of cleaning out the throttle body tomorrow to see if that helps. I also notice that every time i disconnect the battery for some time it seems to go back to a normal idle but eventually go high again. Any ideas what it could be?

 

When you disconnect your battery for a period of time the PCM resets itself and so the jeep learns everything again. Sounds like the PCM isn't liking something. Any trouble codes?

 

only ones have been evap emissons that has been checked out, looks like my leak detection pump is leaking internally.

 

Go to a jy and rip out the tps switch them and see if it makes a difference.

 

you have a vacuum leak, look for a vacuum leak, if you dont see any bad vacuum lines try this: plug the break booster vac line reset the computer with the battery again and drive it around.

 

Checking the TPS was on my list, I have a buddy with another 01, I'll see if he will let me borrow his TPS for a few haha.

 

sounds like vacuum bud. go through all the vacuum lines. plug the brake booster as stated. if the diaphram in it is punctured it will let air by.
hows your brakes feel? pedal hard when you try to stop? or is it easy to press?

 

Know this is an old thread but i have updates. I have yet to check into the TPS thing but I have replaced the brake booster. I did that today. It still is acting up, though not as bad. Sometimes it will idle at 1000, and if put into park or neutral will rev to 1500 tops. I do have a bored tb and am wondering if has anything to do with it. Any help would great I really just want this running right. What kills me is that after I unplug the battery it will run just fine for the first couple of drives.

 

this works with vacuum also does itnot

 

That I do not know, but when I had one of the techs from the local jeep dealership check it out, he didn't say anything about it possibly being responsible for the vaccum issues. I will call him tomorrow and ask about that. Thanks.

 

its part of the charcoal canister system which that has vacuum going to it

 

Well ill check it then, but I dont see how it could affect idle as much as it has. plus the idle issues are everytime. some trips it will run just fine, others it will idle at 1000 and rev higher when put into park.

 

I got this same exact problem man

 

I know this is a dead-thread, but I think some Leak Detection Pump code issues should be addressed since I have watched several videos today on the issue and fixed my own problem (which was self-inflicted from me tinkering with the charcoal canister lines in the past).

The leak detection pump is a pump that cycles open and closed to let air come in to mix with the gasoline vapors before being vacuumed in to the intake manifold.

The (fat) hoses are known for cracking, and the metal fuel vapor line that runs from the tank to the charcoal canister is known for rusting until it leaks vacuum (if you live in the humid rainy environments, or anywhere in the North East US). Those are the most common.

If you take yours out, flex the fat hoses while they're off. If you see cracks-forming from the inside it's time to replace them. I cleared the code after I fixed my issue but now I have an intermittent high idle while in park or neutral I suspect is from the semi-dry rotted fat lines on the leak detection pump itself in the engine bay. I think me flexing them while pondering whether or not to replace them for too long opened up for letting air through.

And BTW, I have a modified IAC while this is occuring. After two IAC failures I took them both apart and JB welded them together inside and out so they'll never choke the engine or idle too high. I actually had the IAC completely removed from the TB with a loud-*** hissing vacuum leak and the engine idled normal as if nothing was wrong at all. The only issue I had was while driving; it ran too rich because the excess air made the O2's input more fuel, so it ran rich enough that while at mid throttle speeds it bogged the engine down.

After that I decided it was OK to just JB weld it in the most wide open position the plunger would move and it isn't been an issue since. I have a wideband O2 sensor so I can see my AFR's to help identify problems. I have 14.7~ very regularly with my cheap IAC mod.

I said all that to say just because the idle is high doesn't mean it's necessary an IAC problem.

 

I agree and would say vacuum leak!