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Ted G.
Ted G., ASE Certified Technician
Category: Cadillac
Satisfied Customers: 6089
Experience:  20 years auto repair experience, ASE Master Tech, Mechanical Failure consultant, Expert Witness
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Car is a CAD 2007 SRX 3.6. When I turn ON the air

Customer Question

Car is a CAD 2007 SRX 3.6. When I turn ON the air conditioning while the car is idling, the car starts missing really bad, the car actually lightly shakes. I noticed at night when stopped at an intersection, the lights dim at the time it is missing. Just had a new battery put in and it seemed to help at first. 3 days later it is doing the same thing again. When missing really bad, I turned off the air conditioning, it does the missing just a little bit. Does not do a hardly at all. When driving 10 mph or more it does not do it at all. While idle, I can press the gas pedal slightly while holding the brake and bring the car up to the # ***** RPM and it almost stop the surging shake. Once it drops back to the normal idles at about .5 RPM it does does the missing and slight shake again. I had a check with a code reader, I was told it was the catalytic converter that it needs to be changed. Yes, catalytic converter may need to be changed, but I do not think that is the problem. Do you think possibly it's a loose belt on the alternator? I had all new spark plugs put in and was told that it is not valves. I was told I could go ahead and drive the car, but when I get on the freeway to really get on it to blow out the catalytic converter. Thanks for your feedback!
Submitted: 1 year ago.
Category: Cadillac
Expert:  Ted G. replied 1 year ago.

If the car still has good power on acceleration and can reach over 3500 rpms then it is not likely the catalytic converter. More likely you have varnish and carbon build up on the throttle body that is not allowing the computer to properly control the idle. The throttle body needs to be cleaned carefully and that should free up the plate at low engine speeds and smooth the idle out.