Idle problem when hot

Dzrtrat1111

Dzrtrat1111

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Out in Ocotillo now and have developed a new issue. Cold start all is well. When the engine is up to temp and I restart it, the rpm shoots up to about 2000 and hangs there for about 10 seconds before coming back down. Also with engine warm, when I come to a stop with engine idling, the rpm sometimes surges a few hundred rpm up and down. Both issues are new this trip and otherwise running great. 
 

Vaccum leak, tps sensor or ??

 
vac leak possibly, check bolts on throttle body also. iac could be taking a crap too.

 
FWIW, my engine cover is held on with little bolts in these 3 stand offs.  the engine cover hit the trunk & broke the rear/forward one of these off of the intake (by the TB, under the oval).  it was glued onto the intake.  The engine cover held it all together, but when the engine got warm it would expand & unseal.  "JB Weld, plastic edition" & it was good to go. 

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IAC. 
My engine did the same thing.

Get a GM IAC. The autozone ones don’t always work right. 

 
If it’s an LS: Ac delco part number 17113598 for the 102 tb. 

 
lincster said:
IAC. 
My engine did the same thing.

Get a GM IAC. The autozone ones don’t always work right. 
Click to expand...
i seriously doubt any damn AZ sensor works right. my buddy has been troubleshooting a no cruise and no OD in his transmission, replaced the brake sensor on pedal under warranty, same result. FINALLY bought an OEM ford sensor, problem fixed, after he tore half the damn truck apart lol

 
Anyone know how to test the IAC with a multimeter? Can’t find anything specific for an LS on the web. 

Additionally, no difference in hot start RPM with IAC unplugged or plugged in  

For reference, engine is an LS3 with CMB DBC TB. Also, I tried hooking up the CBM Mefi pro scanner. No fault codes found and otherwise the program sucks and is very laggy. 

 
Kind of sounds like it's bad. Have you replaced it?  Maybe swap one from another buggy.  

 
I haven’t replaced it yet. Looking for the part number now. I’ll check the part number @BONES gave but I don’t have a 102 TB, my TB is 95 I think so not sure if it is the same. The only numbers on my current IAC is 121. 

 
Don't know if this will help, but I had an issue on a new to me LS car where the cold idle was OK but hot idle was going nuts (like 2400 rpm). I changed the IAC and it didn't make a difference. Then someone who knew what he was doing told me that if the TPS senses over a certain small angle the ECU won't try to adjust the idle with the IAC (it thinks you must have your foot on the gas). At his suggestion I backed off the the throttle stop screw a bit (I think maybe a couple of turns, can't recall exactly) and that fixed it.

 
The IAC or TPS would be my guess. As for your tune, nobody in my group had good luck with them. Of coarse, a few years later, our buddy Lance ( Doonhoon ) got into tuning. He would be the guy I would take it to for tuning!

 
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