Try Cleaning Your Throttle Body .happend To Me Not With Exhaust But When I Remove Program From Truck I Thought I Mess It Up. But With 5 Bucks And 10 Minutes Problem Gone. Idle Was Low Ac Would Not Blow Cold .when Driving Everything Ok It Even Stall On Me . Just Acted Up When Something Else Was Done Good Luck.

 

it's really not a noise, it's just a vibration. It's not a harmonic, as I know the difference.
It's definately a low idle I think. Not 100% sure but pretty sure. I idle right at 600 rpm's currently. I thought it was suppose to be 650, but not sure.
I get perfect A/C temps at idle as well.
I'll try a throttle body cleaning first, but it should be clean.
It idles faintly rough without A/C, but the roughness increases with the addition of A/C.
I'll check all pulleys as well.
Basically, I would like to know what the correct idle should be on a SS LQ9 motor?


Jim

 

Less backpressure, idle could have dropped some.... PCM still hasnt cracked the TB to compensate..... You didnt touch the motor when you put the exhaust on, so kinda wierd if you ask me. Plus this is the first Ive ever read about a problem like this.

 

backpressure was what I was thinking too.

 

Did you ever figure out what the problem was? I have this same exact symptom...

 

Yes, had idle raised to 700 rpm's.

Jim

 

It may have just been raised to 650. Just have a tunner raise it until the vibration goes away with and without the A/C on.

Jim