Q: Rough idle when electrical is used

asked by on June 20, 2017

My car has a rough Idle whenever I use anything that requires power in the car, AC Turning on, Using Power Windows, or turning on headlights. It is most noticeable when the car is idling at a stop or when i let off the gas in traffic, however there is sometimes a slightly noticeable loss of accelerating power. This rough idle and issues happen most of the time, but sometimes they do not, for unknown reasons. It sometimes sounds like it is going to stall, but it doesn't. I replaced my battery about 2 years ago (died while parked less than one day, has not died since) with no difference and had my alternator tested and they said it was fine(at O'reilly, so I don't know how accurate). Where should I start looking? I have already taken it to one mechanic who couldn't figure out the problem, so I want to see if this is something I can check myself before I take it in again or what I should tell the mechanic to look for?

My car has 95000 miles.
My car has an automatic transmission.

Hi there. As electrical components and accessories are used, more draw and strain is placed on the motor to power the alternator. As such, existing small idle problems will be accelerated when the engine is asked to give more. In most cases, a rough engine idle is caused by a vacuum leak, dirty fuel injectors, EGR valve, mass air flow sensor or problems with the idle control valve. It would probably be best to have a professional mobile mechanics complete a rough idle inspection at your location to pinpoint the source of your problem.

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