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Unread 11-10-2008, 02:00 PM   #1
peeweeXJ
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2002 4.0 Rough/High Idle When Cold

My TJ has about 100k miles on it. And the Idle/startup blows compared to my 200k XJ.

No codes

It usually has the poor idle when it has been sitting for 15 hours+ (the length of time I am at work)

I will start it up and it will stumble/misfire on it's way to it's high idle.
It will idle at 1k rpms, until it warms up. The engine will occasionally try to idle down, but then it starts to stumble over itself, and goes back up to 1k.

If I start driving when it's cold, I will push in the clutch, and the RPM's will hold at what they were, or even go up slightly, then slowly start going back down to 1k.

I did clean the TB/IAC after this all started, but nothing changed.
Plugs are perfect.
Have run a couple tanks through it, with different octanes, from different stations.



I also have a related/unrelated? ticking noise that comes and goes when cold.
The ticking will increase with RPM's, and seems to quiet down (not disappear) when the engine gets to running temperature.
I will cruise down the road at 1500 rpms and the ticking will vary in loudness.
You can hear the ticking at idle in the cab with the radio off. You can hear the ticking at high RPM's with radio on, which is really annoying.
If I start the engine up cold, and the ticking is not there, it will show up if I rev it really high.
It has also been the other way around, where I start it cold, and it's ticking, and I'll rev it up really high, and the ticking will go away.
It has the correct/right amount oil, and I have run Rislone and ATF through it. Clean Mopar filter too.
I have also checked exhaust bolts.

I have taken a automotive stethescope to the engine and could not locate the ticking. Sounds like valvetrain though.

Could the idle problem be caused by a bad TPS or IAC? Maybe CKP?

Thanks for the responses

btw- this is not normal for a Jeep, if that's all you have to say.

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Unread 11-10-2008, 02:18 PM   #2
PJL
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I had a similar problem with my idle. No ticking, though. I replaced the TPS and the IAC and it was fine after that.
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Unread 11-11-2008, 01:45 PM   #3
peeweeXJ
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So you replaced both of them at once? So you really don't know which one fixed it?
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Unread 11-12-2008, 11:34 AM   #4
peeweeXJ
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I will try and get a video soon.
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Unread 11-12-2008, 11:56 AM   #5
Wif
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Quote:
Originally Posted by peeweeXJ View Post
My TJ has about 100k miles on it. And the Idle/startup blows compared to my 200k XJ.

No codes

It usually has the poor idle when it has been sitting for 15 hours+ (the length of time I am at work)
I will start it up and it will stumble/misfire on it's way to it's high idle.
It will idle at 1k rpms, until it warms up. The engine will occasionally try to idle down, but then it starts to stumble over itself, and goes back up to 1k.

If I start driving when it's cold, I will push in the clutch, and the RPM's will hold at what they were, or even go up slightly, then slowly start going back down to 1k.

I did clean the TB/IAC after this all started, but nothing changed.
Plugs are perfect.
Have run a couple tanks through it, with different octanes, from different stations.



I also have a related/unrelated? ticking noise that comes and goes when cold.
The ticking will increase with RPM's, and seems to quiet down (not disappear) when the engine gets to running temperature.
I will cruise down the road at 1500 rpms and the ticking will vary in loudness.
You can hear the ticking at idle in the cab with the radio off. You can hear the ticking at high RPM's with radio on, which is really annoying.
If I start the engine up cold, and the ticking is not there, it will show up if I rev it really high.
It has also been the other way around, where I start it cold, and it's ticking, and I'll rev it up really high, and the ticking will go away.
It has the correct/right amount oil, and I have run Rislone and ATF through it. Clean Mopar filter too.
I have also checked exhaust bolts.

I have taken a automotive stethescope to the engine and could not locate the ticking. Sounds like valvetrain though.

Could the idle problem be caused by a bad TPS or IAC? Maybe CKP?

....

btw- this is not normal for a Jeep, if that's all you have to say.
What the hell do you do for a living to be working 15+ hours

First thing ..

The crap idle and revs holding up does sound like IAC.

Secondly ..

The ticking does sound like tappet noise .. and this one is normal for a Jeep
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Unread 11-12-2008, 12:09 PM   #6
peeweeXJ
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Quote:
Originally Posted by Wif View Post
What the hell do you do for a living to be working 15+ hours

First thing ..

The crap idle and revs holding up does sound like IAC.

Secondly ..

The ticking does sound like tappet noise .. and this one is normal for a Jeep
I work at a mine, and I have a 13hr. shift + 3 hrs. on a coach bus to get there.

A tappet noise is consistent, it is not like a wristpin where it quiets down as it heats up.
It might be normal noise if people didn't look at me when I started it up.

Thanks
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Unread 11-12-2008, 12:24 PM   #7
Wif
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Quote:
Originally Posted by peeweeXJ View Post
I work at a mine, and I have a 13hr. shift + 3 hrs. on a coach bus to get there.

A tappet noise is consistent, it is not like a wristpin where it quiets down as it heats up.
It might be normal noise if people didn't look at me when I started it up.

Thanks
Hydraulic tappets do this .. they can tap when cold due to oil starvation or incorrect viscosity oil, or tap when hot due to low oil pressure or incorrect viscosity oil.

Sometime noisy tappets can be caused by a faulty oil filter .. the anti-drainback valve letting all the oil from the oilways drain back into the sump.
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Unread 11-12-2008, 12:44 PM   #8
peeweeXJ
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Quote:
Originally Posted by Wif View Post
Hydraulic tappets do this .. they can tap when cold due to oil starvation or incorrect viscosity oil, or tap when hot due to low oil pressure or incorrect viscosity oil.

Sometime noisy tappets can be caused by a faulty oil filter .. the anti-drainback valve letting all the oil from the oilways drain back into the sump.
That doesn't sound like a normal condition to me? Key words like low, starvation, incorrect, faulty.
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Unread 11-12-2008, 01:09 PM   #9
Wif
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Quote:
Originally Posted by peeweeXJ View Post
That doesn't sound like a normal condition to me? Key words like low, starvation, incorrect, faulty.

Normal doesn't mean correct .. most of the 4.0's do it. I was giving you examples of what can exaggerate the problem.

I'll wait for someone else to jump in here ..
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Unread 11-12-2008, 01:16 PM   #10
grinwa
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Is it possible you have an exhaust leak? Check for one. If it get louder under a load and less when coasting, it could be an exhaust leak. That could cause problems with the O2 sensor, too.
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Unread 11-12-2008, 01:35 PM   #11
peeweeXJ
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I have thought about an exhaust leak, but I checked as good as I could visually, and tried to tighten all the bolts that I could. They were all good n' tight. I'll go check again.

BTW- I ran it with the IAC unplugged and it made no difference. Still idled high, and tried to come down but stumbles.
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Unread 11-12-2008, 02:25 PM   #12
peeweeXJ
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Haha, well I believe to have found my ticking problem. Had my stethescope out and was scoping around the engine. Could not tell where the ticking was coming from. Put my hand on the EVAP purge solenoid, and hole e crap does it ever tick. Could it actually be the really loud thing I hear when I start it up on cold mornings (4-6 LOUD ticks)?

Anyhow- Still not sure on the high idle/slight stumble. Seems like a rough spot, not exactly stumbling.

Thanks
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