Rough Idle

suicideking

suicideking

TJ Addict
Supporting Member
Joined
Mar 7, 2019
Messages
2,240
Location
Riverside, CA
2004 TJ, 4.0, auto trans.

I get a rough/shaky idle. Its not bad when in park or neutral but when I'm at a stop in gear, like a stop sign or red light, it vibrates pretty good.

While this is happening, I can pop the gas pedal just a bit and the vibration will stop. So I've gotten pretty good at leaving a little room in front of me at a stop light so I can tap the gas pedal.

Only repairs I've had done: Recently the check engine light came on and it ended up being the cats. Had the cats replaced. It runs perfectly fine while driving. Just the problem with idle when stopped.
 
First, cheapest, and easiest step is to grab some throttle body cleaner and clean your IAC and throttle body. See procedure in the how to threads. Check back in if that doesn't work.

Curious, did this rough idle just start after you had the cats replaced?
 
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Mac57 said:
First, cheapest, and easiest step is to grab some throttle body cleaner and clean your IAC and throttle body. See procedure in the how to threads. Check back in if that doesn't work.

Curious, did this rough idle just start after you had the cats replaced?
Click to expand...

It did start after the cats were done.
 
suicideking said:
It did start after the cats were done.
Click to expand...

You had a CEL which led to cats being the issue, they were replaced. I'm thinking the computer was altering the air /fuel mixture with the bad cats. Now that you have new cats the computer has to relearn. To speed that up disconnect the negative battery cable for an hour which should reset things back to base. Double check to ensure any codes have been erased as well.

And clean the IAC and throttle body as well, can't hurt.
 
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