Topic: Idle Issue

[Desert Bob]

My 1995 YJ 2.5L has issues at idle. It runs well but it idles rough (kind of pulses) and when started when it is warm it idles high (1500rpms). As soon as I drive off the idle drops down to normal (750-800 rpms). When it is cold it acts like it is going to stall out (but never does). I cleaned the throttle body, IAC and passage and ran some injector cleaner (sea foam) through it but is still acts exaclty the same. Is this the TPS or IAC that controls this circut? The Jeep has 163,000 miles and to my knowledge neither of these have been changed.

[Jeffy]

The IAC is what controls the idle when the engine is cold.  Once it's warmed up it I believe the IAC closes.  (like a choke)  Does the engine idle fine when it's warmed up?  The high idle would lead me to believe there is a vacuum leak someplace.  Although you said it drops back to normal after a while.

I'd consider checking the PCM for stored CEL codes.  Even if they don't cause a CEL there could still be codes.  Here's how to do that: http://4bangerjp.com/forums/index.php?topic=3419.0

[Desert Bob]

The engine idles OK when warm but it kind of pulses.  Not a wide swing in RPM but enough that I can feel it.  It is rough and stumbly () when cold.  I just replaced all of the vacuum lines and have checked for leaks on the manifold by using brake cleaner around all of the seals.  No issues there.  Plugs are a nice tan color. I will see if there are any codes tonight.  Thanks.

[lanulos89]

my heep idles at 1 grand all day long 

[Jeffy]

my heep idles at 1 grand all day long 

Living with a vacuum leak? 

[Desert Bob]

The codes were  12 and 33.  The 12 makes sense as my battery was disconnected over the weekend when I replaced my lifters.  I have no idea what the 33 is since my manual would lead me to believe I don't have the part effected.  Any help?

[lanulos89]

my heep idles at 1 grand all day long 

Living with a vacuum leak? 

you are correct im just too lazy to fix it, it runs so why bother?

[jfrabat]

Mine is ussually at around 900~1,000 RPMs (dash reading).  What is the normal RPM range?

[Desert Bob]

My past jeeps have always idled at around 700-750rpm.

[Desert Bob]

Checked the plugs and everything look as they should.  Light brown on the electrodes.  Any other ideas?

[brokenwrist21]

a rough stumbling idle would lead me to believe, fuel filter is it's never been changed. maybe a possible misfire these have lots of causes, bad wires, in the ignition somewhere etc. but lets keep it simple, fuel filter change it if it hasnt been changed. and i suggest heading over to your closest jiffy lube, and have them do a fuel system cleaning, its a two step process, more than just adding stuff to the tank. and just to make sure your timing is correct stick a timing light on it and check it.

[Desert Bob]

Wouldn't a bad filter cause issues under hard acceleration?  The Jeep runs fine once off idle.  I was planning on doing new plugs, wires and cap/rotor in a couple of weeks so I will replace the fuel filter then.  I just got my Rubicon Express 2.5" lift kit so that will be this week-ends project.

[Desert Bob]

I replaced the Cap, rotor, plugs, wire and fuel filter and it runs better but still idles poorly.  Would an O2 sensor cause this type of behavior.  BTW: Did a compression check and it goes as follows:

1st 157psi
2nd 155 psi
3rd 162 psi
4th 165 psi

Is this good for a motor with 164K miles?

Help!

[Jeffy]

I replaced the Cap, rotor, plugs, wire and fuel filter and it runs better but still idles poorly.  Would an O2 sensor cause this type of behavior.  BTW: Did a compression check and it goes as follows:

1st 157psi
2nd 155 psi
3rd 162 psi
4th 165 psi

Is this good for a motor with 164K miles?

Help!

I think your compression is pretty good for an engine with that many miles.  I forget what the variance between cylinders is...  gotta look that one up.

Go to the FAQ and look up Factory Service Manual and download the 94 or 95 pdf's.

[garydubf]

Have you tried using propane at all of your vacuum connections?  That'll help you determine wether you have a vacuum leak.  If you still have the axle disconnect, don't forget to check there!!