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- - High Idle (http://zr1.net/forum/showthread.php?t=27447)

TealZR1

01-26-2017 06:44 PM

High Idle

Fighting a high idle around 1100 when hot. Troubleshooting now replaced PCV Valve rubber and tightened up all hoses.
Saw where an easy troubleshoot would be to change the IAC Valve on top of plenum possible problem. Is this as easy as it looks? Could it be the issue?
Thanks to all in advance.

Roadster

01-26-2017 06:57 PM

Re: High Idle

Quote:

Originally Posted by TealZR1 (Post 256596)

Just had a similar issue with my 94 after the Plenum pull last weekend. Engine would sometimes idle at 1000-1000 rpm's and then sometimes at 800 rpm's. Ended up taking out the IAC and giving it a thorough cleaning. Had a lot of carbon build up on it. Replaced and all is good. Starts and revs up to 1500-1700 rpm's and comes right back down to 700 rpm's for a perfect idle. Also cleaned inside of the opening in the plenum/throttle body area where the IAC is seated. It is as easy as it looks......

mike100

01-26-2017 07:22 PM

Re: High Idle

It is probably one of the large vacuum lines under the plenum...the gas tanke purge system lines- they sometimes pop off if there is a backfire or some similar event.

msuhanek

01-26-2017 07:54 PM

Re: High Idle

Thanks roadster and Mike 100 for the quick reply. Those are my final two options. Will look at the IAC valve this weekend and pull the Plenum down the road if needed

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mike100

01-26-2017 11:25 PM

Re: High Idle

it has been talked about before (do a search), but if you take off the air duct and block the throttle body with a stiff piece of cardboard or a phone book (anybody still have one of those?) the engine should stall. if it still runs, you can clearly locate the vacuum leak noise under the plenum.

BigIke

01-27-2017 08:43 AM

Re: High Idle

My hunting and high idle was caused by the large vacuum line under the upper plenum. I zip tied the hose to the plenum nipple.

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Roadster

01-27-2017 10:52 AM

Re: High Idle

I stand corrected, just took the 94 out for a ride, and close to the same thing on the idle. Sometimes coming to a stop idling at 1000-1100 r's. Other times around 800-900r's. So it looks like cleaning the IAC really did not have any effect on the idle, at least for me.....

secondchance

01-27-2017 11:56 AM

Re: High Idle

Quote:

Originally Posted by Roadster (Post 256606)

I stand corrected, just took the 94 out for a ride, and close to the same thing on the idle. Sometimes coming to a stop idling at 1000-1100 r's. Other times around 8-900r's. So it looks like cleaning the IAC really did not have any effect on the idle, at least for me.....

Start by checking throttle body for possible binding. Also, check TPS voltage with throttle body closed.

Roadster

01-27-2017 01:00 PM

Re: High Idle

Quote:

Originally Posted by secondchance (Post 256609)

Start by checking throttle body for possible binding. Also, check TPS voltage with throttle body closed.

Copy that....will do.....

lfalzarano

01-28-2017 01:07 PM

Re: High Idle

Or you can send it to Marc! He fixed mine.

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