Motor wants to idle at 2000rpm


gubernathss

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So I change my power steering pump I had to takeoff my air cleaner box to do it. Now my engine wants to run at 2000 RPMs when I have the clutch in, an in gear when I engage the clutch it drops down to normal but as soon as I put the clutch in it wants to run up to 2000 again I’ve checked for vacuum leaks there’s no hoses missing or loose
 

Gilaguy23

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I'll take a poke at this one. Thought #1. You accidentally disconected the or TPS plug(s) #2, one of the vac line elbows split and you havent found it yet. #3 The power steering system has a pressure switch in it to accommodate loaded conditions. You knocked the wires off the switch. Would help to know what year and engine as well.
 

Gilaguy23

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That is weird its only when the clutch is in it idles up. Basically the Idle air control motor is what controls the idle speed unless things are so far out of bounds like massive vac leaks or stuck throttle linkage/cable/pedal. The IAC is located on the throttle body as well as the throttle position sensor. If you unplugged any of these when working on it and turned the key on they may need to be reset we'll say. Unhook the battery and let it sit a while which is supposed to completely nix the computers memory. Some say also take the + battery cable when disconnected of course and touch it to a ground somewhere to kill off any parasitic voltage in the system. Post up what you find, were all curious and learn from others delimas ya know.
 

machoheadgames

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Sounds like a bad IAC to me. Sometimes they can be cleaned to restore their functionality, sometimes they can also break though. I accidentally broke my original IAC while I was cleaning it, and then it idled at 3000 and if I left it in gear it wanted to really fight my brakes. New IAC fixed it right up.
 
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gubernathss

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Ok so I’ve once again gone threw the Jeep looking for vacuum leaks, replacing two hoses that didn’t seem bad but I didn’t want to chance it, also replaced the, O2 sensor, the MAP sensor, idle airflow sensor, an the throttle position sensor, with no change, I’ve also disconnected the battery an left it out of the Jeep over night then reconnected it with no change, start it up it idles at 1400 rpm, then start driving an as soon as you push in clutch it will jump to 2000 rpm until you let the clutch out an it goes back down also don’t know if this connected my radio quit working
 
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gubernathss

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That is weird its only when the clutch is in it idles up. Basically the Idle air control motor is what controls the idle speed unless things are so far out of bounds like massive vac leaks or stuck throttle linkage/cable/pedal. The IAC is located on the throttle body as well as the throttle position sensor. If you unplugged any of these when working on it and turned the key on they may need to be reset we'll say. Unhook the battery and let it sit a while which is supposed to completely nix the computers memory. Some say also take the + battery cable when disconnected of course and touch it to a ground somewhere to kill off any parasitic voltage in the system. Post up what you find, were all curious and learn from others delimas ya know.Ok so I’ve once again gone threw the Jeep looking for vacuum leaks, replacing two hoses that didn’t seem bad but I didn’t want to chance it, also replaced the, O2 sensor, the MAP sensor, idle airflow sensor, an the throttle position sensor, with no change, I’ve also disconnected the battery an left it out of the Jeep over night then reconnected it with no change, start it up it idles at 1400 rpm, then start driving an as soon as you push in clutch it will jump to 2000 rpm until you let the clutch out an it goes back down also don’t know if this connected my radio quit working
 

Gilaguy23

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Man I feel for ya. Similar problem with my 91 after being nice and replacing the TPS for no good reason. To date, 3 TPS'es, one of which is a Mopar one. 2 IAC's, pull the TB twice and regasket just to be sure. Inspect and reinspect the IAC port and still it idles at 1100+ moreless unless it sits idling for several minutes at which point it comes back down to 800 maybe. if its rolling and out of gear or in gear with the clutch pushed in it idles around 1400 until dead stopped again. I gave up on trying to figure it out. Uuugg.. thats what I get for fixing what aint broke.
 

machoheadgames

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YJs are a mess as far as idling is concerned. While y’all are staying too high, my 4.0 has always dipped way low over the years at random stops. And by low I mean like 300 rpm, feeling like it’s going to die, shaking the whole Jeep the entire time. I have changed virtually everything including the PCM. No changes whatsoever.

Part of me thinks it’s a physical issue, like the timing chain or something. Hard to say. I recently put a New double roller timing chain so we’ll see if that helps.

This whole post is to say that no one seems to have a similar experience, and for whatever reason, I can not establish what is “normal” as far as idling in a YJ goes. The TJ was MUCH better about this, they all idle at 750 on the dot pretty much no matter what. Very comfortable and solid feeling. I think the more modern tuning of OBDII engine management contributes a lot to that. The very rough edges of OBDI probably aren’t capable of running an engine super smoothly.
 
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gubernathss

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I'll take a poke at this one. Thought #1. You accidentally disconected the or TPS plug(s) #2, one of the vac line elbows split and you havent found it yet. #3 The power steering system has a pressure switch in it to accommodate loaded conditions. You knocked the wires off the switch. Would help to know what year and engine as well.
New to jeeps we’re is the pressure switch located on a 95 Yj 2.5L
 

machoheadgames

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New to jeeps we’re is the pressure switch located on a 95 Yj 2.5L
I don’t have a 2.5 but pretty certain it’s threaded straight into the back of
The pump, or on the line coming out of the pump. If you look for it you should see it. It would be the only wiring going to the pump itself. There will be other wiring going to the O2 sensor nearby but that will mostly obviously dip down below the engine and intake manifold.
 
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gubernathss

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So Napa has one for 40 bucks an as much as I love tinkering with engines, we got a shop in town that just repairs Jeep’s, if it doesn’t fix it I’m dropping it of Tuesday, I’ll let you know what they come up with
 

Gilaguy23

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Do some reading and you'll find a way to test the switch. On my 91 it is on the power steering line itself. Not hard to spot once you look. And its only on the 4 cly jeeps also FYI.
 

cas

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My '88

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Please ignore the rust preventative coating on everything. ;)
 

Gilaguy23

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Thats it. Its purpose on the 4 cyl is to increase the rpm at low speeds or idle to compensate for the load on the engine from the PS system. Given your increase in rpm sorry to say I dont think this is the culprit after some more investigating. Sounds like were not the only ones with odd ball rpm problems either. The cure even after reinstalling the original working parts has me stumped. Only thing Im concerned about is if someday my state demands smog checks, I doubt it would pass idling above whats considered the factory spec.