My car idles rough at red lights and even worse when the air conditioner is on. on 2004 Chrysler PT Cruiser

The oil has been changed every 3000 miles or so and we even replaced the spark plugs!I was told the've never seen plugs so worn concidering their was only around 65,ooo miles on the car. Goes through alot of oil. Engine came on for the first time recently while pulling a hill, and then went off. Popped on again briefly a day or two ago. We've used STP, WHICH DOESN'T SEEM TO HELP.

by in Roseville, CA on October 10, 2013
1 answer
ANSWER by on October 11, 2013
There are multiple things that may contribute to it idling rough. When you turn your air conditioning on it ads more load to the engine, and also the a/c compressor pulley is engaged. You may have a vibration from weak motor mounts, or the engine may actually be running rough if the air or fuel mixture is incorrect. I would recommend a diagnostic inspection, so you don't have to keep guessing at repairs.