JCRAMOS

Hi, I have a 03 Tahoe that is giving me problems when I turn on my A/C the engine start to idle up and down this would stop if turn off the A/C, also the A/C some times blows hot air when I have the rough idle issues, I have 95,000 miles on it I have not re-filled new refrigerant. Anyone knows what is going???

in2pro

I'd bet you need to clean the throttle body, its probably got a fair amount of build up and is causing the unstable idle.
Just did this on my sisters 03 suburban and it fixed it right up

JCRAMOS

The unstable idle is only when the A/C is on, and sometimes the a/c blows hot air, the idle issue and A/C hot air issue happens any time of the day, like yesterday afternoon when it was 100 degrees in LA.

in2pro

The low RPM's is causing the AC clutch to dis-engage at idle and if the AC works fine at highway speed or when you are driving them I am almost certain its the crud build up in the throttle body.

Pull the air cleaner off remove the throttle body and if the back side of the throttle plate is black and the inside of the intake is covered in black goo, clean it out and re-assemble and the surging should clear up.

in2pro

Here is the bulletin...

Bulletin No.: 04-06-04-040
Date: June 14, 2004
TECHNICAL
Subject:
Idle Instability, Low or Rough Idle with Electronic Throttle Control (Clean Throttle Body)
Models:
2002-2003 Cadillac Escalade, Escalade EXT
2000-2003 Chevrolet Silverado, Suburban, Tahoe
2002-2003 Chevrolet Avalanche
2000-2003 GMC Sierra, Yukon, Yukon XL
with 4.8L, 5.3L or 6.0L V8 Engine (VINs V, T, Z, N, U - RPOs LR4, LM7, L59, LQ9, LQ4) and Electronic Throttle Control
Condition
Some owners may comment on an idle instability, low idle speed or rough idle.
Cause
Condition may be caused by deposits in the throttle body bore.
Correction
Clean throttle body bore and throttle valve plate of carbon using a shop rag and an appropriate cleaner. Refer to Engine Controls Repair Procedures - Throttle Body Cleaning Procedure. This procedure may be performed at any mileage necessary. Check to determine if the PCM calibration has been previously updated to one that includes the update for throttle body coking. For 2003 model year vehicles, look in the operating system portion of the calibration. For 2000-2002 model year vehicles, look in the engine portion of the calibration. If not, then update the PCM calibration to the latest calibration.

JCRAMOS

Hi, I clean the throttle body this weekend and so far so good I haven't had any issues with the up and down idle, Thanks a lot. I have this other issue with the A/C, I thought the throttle body cleaning would take care of it but it didn't. I have this occasional problem with hot air blowing out the a/c when it should be cold, if I turn off the car and turn it back on the problem goes a way, any ideas? Thank you. 2003 Tahoe, 98,300 miles.

73shark

Might be low on freon and the low pressure switch is turning off the compressor.

JCRAMOS

Do you know approx. how many R134a cans it would take fill it up the A/C? I have never fill it up before, since I bought new. Thanks.

in2pro

Check on the R134a kit that they have a most auto parts stores and I think it gives you a guide line.
I would start with no more then one can and see what the results are, if you still have the issue then a AC professional may need to look at it.

new2me

IF you are low on freon then you have a leak.It maybe very slow but there is a leak.You can even buy kits that have dye and a uv light if you want to do some of the trouble shooting yourself.If you look under your hood there is a sticker that tells you how many pounds the systen takes,Your system doesnt sound empty just low,If you add freon yourself add enough to get the compressor turning then let it idle about 10min or so to let the pressures stablize then add freon to system.