I just completed my second trip on the my car and the car ran very well except for this idling issue that I have been troubleshooting. I have a idle issue that only happens once and awhile.. Maybe around 30-40% of the time... It only happens at operating temp (180 - 210) and never has happened in my driveway or loading the car. The issue is that the idle bounces very consistent from 800 to 1200 and back to 800, etc.. Sometimes if I rev the motor it will disappear. I can not correlate anything that causes it.. Do I maybe have a bad IAC? I never have the issues while driving even if I run at 1500 RPM it sounds perfect and runs very strong (no popping, etc)..

Thank you!

throttle plates are closing to far and not letting enough air in drill a small hole in the throttle plate

Very interesting... how big? Any particular location? Thank you!

There is a already a hole. Meanbluedragon will know the proper size to drill it out to..PM him.

bottom center about 3/4 inch up 1/4 inch worked for me

The car is still in the toy hauler and don't recall there being a hole... Gotta check..

Interesting..... mine kinda did the same thing last weekend.
I ran up patton a few times then stoped on top and it died. Started it again and died, then started it but feathering the throttle and it stayed running but as soon as i let off the throttle it died. I let it rest 10-15 min and ran perfect the rest of the time. I wonder if i have the same issue as you

the 90 mm throttle bodies do not have that hole it needs to be drilled a stock unit already should have it

mine got stuck at high idle a couple of times gonna have to check with cbm......................................

Interesting... Mine has never died though.. I think it is hole thing that is screwing me up.. Not sure why my does not have one. . Gotta talk to sandzilla.

Had an issue pretty similar. idle up and down intermitten at first then always when it was hot but never when you started it up. Then I started getting high idle on start up with the up and down once it was warm. A buddy took it to turnkey for me and they replaced something on the throttle body that cost $45 and it runs perfect now. I had taken the throttle body apart and cleaned it and this had helped some but then it started again. Call Paul at turnkey, when I talked to him he said they had some similar problems and told me what to clean.

Do not drill a hole in the T/B blade... It sounds like you have a hunting condition with the IAC motor. Also make sure that you T/B is closing all the way when you let off the throttle... I've never had to drill a hole in the blade of a 90mm T/B blade... And make sure your air temp sensor is working properly. If it does not do it when you first start the car, or when the engine is cold, You are probably running on the rich side of your tune...

JMHO,

Zilla

I have a new ls motor with a similar issue (amongst others) just curious who is the builder ?

The engine is from a GTO, not necessarily from a builder.. harness and computer is from CBM.

Interesting comments regarding the air temp sensor. Now I do not have a spot for the air sensor and just tie it off at the back of the wiring harness above the transmission with some zip ties... Any suggestions... it is weird why this issue never happens when the motor is cool..

do you know what they replaced? I think the IAC was the more expensive then the throttle position sensor so it sounds like the IAC..

My buddy has a 450HP frpm CBM that is doing the same thing! Interesting!

Check the fuel pressure regulator, if it is leaking you will get similar conditions. If you have an IAC tool you can shut the pintle and adjust the min idle to somewhere around 450-500 then plug the IAC back in and turn the engine off. When you restart it the computer will set it at the correct idle.

What does IAC stand for?

IAC is Idle Air Controller, but it has several names (ie: ide air motor, idle air bypass, etc.)

well ill tell ya i love my cbm motor i wouldnt trade it for any other motor out there. and i know they are quick to fix issues with there motors they are always concerned about there quality ..........................

mine only did it once or twice but the motor always performs on que

does your car seem to run rich??? blowing smoke??

No, not at all... Always runs good except this idle thang

I have exactly the same condition on my Shortstar... as the engine reaches normal temp the idle speed will start to oscillate. The warmer it gets, the worse it is. I've had the stall/hard restart issue too, a couple times. Other than that the car runs like a scalded ape, couldn't be happier...

Is there a way to test the IAC system or do you just have to replace the sensor?

Like I said above check the fuel pressure regulator, just pull the hose of of it while it is running and see if it leaks. That is what happens when the engine sits for a while.

I'll check that too, thanks