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Q: Rough idle and shaking.

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Truck idles roughly when the cooling fan kicks on, rpms remain steady, if the engine is reved, rough idle goes away and doesnt come back for a while. This occured after the vehicle was taken across an exceptionally rough terrain.

My car has 74000 miles.
My car has an automatic transmission.

This sounds like you may have a slight drop in system voltage as the fans come on. This may be a result of a faulty alternator or voltage regulator. As you may know, the alternator charges the battery and the voltage regulator regulates the rate at which the alternator charges the battery. If either of these are not working properly, this may cause a drop in system voltage when additional draw is needed on the charging system such as when the fans come on. I would recommend having a professional from YourMechanic come to your location to take a look at your charging system.

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