car starts to shudder while stopped at light with the AC on on 2003 Chrysler PT Cruiser

AC works great. Car drives fine. But when stopped at a light for any length of time with the AC on my car starts to shudder and I just immediately turn off the AC which is still working and the car idles fine. Once the light turns green and car starts moving I can turn the AC back on and car and AC work just fine. I worry that this is not good for the engine to keep doing this but can't afford a large repair bill. Any ideas what is causing this? thanks,

by in Houston, TX on July 28, 2010
2 answers 1 comment
ANSWER by on August 17, 2010
I don't know how many miles you have on your vehicle, but you may conside performing a tune up with spark plugs and ignition wires. Also, clean your throttle body bore as this will affect your idle speed especially with the load of the A/C on it. The idle speed motor cannot compensate and correct the idle speed if the throttle body bore is dirty (carbon buidup or coking). You can clean the throttle body yourself if you are mechanically inclined. Remove the intake hose to the throttle body. ENGINE OFF, open throttle blade, shine flashlight in bore, if black with residue, spray some carb/throttle body cleaner on a rag and with your finger, scrub the opening of the bore including the throttle plate. Do not let the throttle plate close on your will hurt! The last thing to have checked is your A/C Charge and compressor drag. You should be able to turn the compressor over with relative ease.
COMMENT by on August 17, 2010
Thanks for the reply. My car has 107,000 miles and has only had one tuneup at 70,000 miles. I don't have a clue what a throttle body is but I certainly can ask the mechanic to clean it as well as changing out the plugs and wires. This has been such a strange symptom but have just been glad that so far it is getting me through the summer here in Houston. I've taken it to two different shops about this problem and they both said the ac was working ok. They just couldn't figure out what was causing the trouble. Thanks again.
ANSWER by on December 31, 2010
That , I am told, is the norm for the PT. We had our air repaired and that is what it does. I checked on line and found this to be true. Just the nature of the beast.

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