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RaZX6R 07-11-2011 03:20 PM

High Idle Issue
Hello all,
I'm new to these forums... my name's Al and just got a 2004 GC Limited...ok well 6 months ago... and couldnt be happier...until 2 days ago when I was driving on the interstate and floored it to get past someone and ever since then its been idleing at 1800 RPM constant in park and neutral.. changed out IAC and cleaned TB....searched for vacuum leaks in the lines and couldnt find anything.. there is a whistling coming from behind the TB and goes away when in gear or the AC is on... checked the throttle cable but thats fine... was told to drive it after changing the IAC so it can relearn idle settings... still idles high... there are no codes being kicked out at all.....when I drove it today the tranny was acting really weird (was not shifting right it seemed). I'm tearin my hair out tryin to figure this out so any info or experiences with somethin like this that you all can help me out with would be great... Thanks:)

01grand 07-11-2011 03:36 PM

Re: High Idle Issue
I would check the throttle position sensor. Could be that it is telling the computer to increase the idle to keep the engine running at idle but im not sure on that one. However, I did have a problem with a sometimes erratic idle, and at the end harsh erratic shifting, and then it threw a code for a bad throttle position sensor. I swapped it out and havent had an issue since.

RaZX6R 07-11-2011 03:39 PM

Re: High Idle Issue
a few people told me to replace the TPS too.... but wouldnt it throw out a code if it were bad?? or is it just that the computer isn't reading it as bad?

RaZX6R 07-11-2011 03:43 PM

Re: High Idle Issue
oh, and it seems ok on a cold start-up then the rpm's go up as the engine warms up

01grand 07-11-2011 04:20 PM

Re: High Idle Issue
It should throw a code but mine acted erratically for a while before the CEL came on. The part only cost me about $35-40 so its fairly inexpensive and very easy to replace. Thats about the extent of my experience, hopefully somebody else will have other ideas.

Frango100 07-11-2011 05:07 PM

Re: High Idle Issue
If you have a scanner you could check the TPS output. Mine in idle normally is at 12%.
When you did clean the TB, did you see that the throttle plate was completely closed? If not, it could be that something is preventing the throttle/cable to return to the full closed position. There could also be a vacuum leak, as you mentioned some noise behind the TB. The PCV line ends somewhere in the inlet duct downstream of the TB, so check this out for loose line or something. Could explain the noise you are hearing. If this is ok, i also would think about the TPS itself.

RaZX6R 07-13-2011 09:56 AM

Re: High Idle Issue
checked the PCV line....and it's totally disconnected at the other end...(behind TB) would this cause the high Idle??? Just makin sure so I dont have to a parts run....Thanks!!

01grand 07-13-2011 11:48 AM

Re: High Idle Issue
It could, fix that first and see if your idle returns to normal.

2005JGC 07-13-2011 12:17 PM

Re: High Idle Issue
if its disconnected from the intake manifold then YES, you have a large vacuum leak that will cause a high idle!

RaZX6R 07-13-2011 02:37 PM

Re: High Idle Issue
That was the problem!!!! Thanks guys for all the help...I woulda never checked that line.... and it was quite the PITA to get at but its all good now.....Thank You All again!!!

01grand 07-13-2011 02:45 PM

Re: High Idle Issue

Originally Posted by RaZX6R (Post 446888)
That was the problem!!!! Thanks guys for all the help...I woulda never checked that line.... and it was quite the PITA to get at but its all good now.....Thank You All again!!!

:thumbsup:You're welcome, glad you got it working! was the tubing damaged or did it just slip off? If it didnt fit on very tight you might want to replace it or use a wire tie or something to keep it from falling off again.

RaZX6R 07-13-2011 02:47 PM

Re: High Idle Issue
replaced was the wrong sized hose on the intake side (too big) and it popped I changed it out with the correct size and a new clamp :)

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