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2003 Mazda MX-5 Miata Cloth 2dr Conv 5-Spd Manual

2003 Mazda MX-5 Miata
Trim Info:
Rear Wheel Drive, 2 Door Convertible, Two Seater
23 mpg city / 28 mpg hwy
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September 27, 2012, 1:52 pm

Kenneth P

Question: Idle rough

My car seems to start idling rough only when the ac is turned on. What could this be?

October 4, 2012, 8:35 pm

Ron W
Expert Mechanic

Could be the engine isn't adjusting the idle to the load of the AC being on. Start with the basics. I would check the throttle body and see if it has carbon build up in it. If it does get some throttle body cleaner and clean the plates by spraying it on a lint free rag and wiping out the plates with the engine OFF.

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January 29, 2013, 2:42 pm

Kenneth P

This did not work. I am starting to think it is the pulley on the alternator giving out. What do you think? Chirping noise when in idle or coming out of lower speeds. Rough idle when any larger electrical load is added on the vehicle. Mainly the windows and the A/C or even just the blower w/o AC.

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January 29, 2013, 6:35 pm

Ron W
Expert Mechanic

Chirping noise can indicate a weak or failing bearing in the alternator. You should have someone listen to it to isolate exactly where the noise is coming from. And have the charging system checked while he's there.

As a side note, I hope the basic tune up items are current. A weak ignition can cause a lot of the issues you are listing (but probably not the noise). Just want to make sure that is already done before we dig to deep. Sometimes the easy stuff gets missed.

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