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Q: truck

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hey so i have 06 f15 my alternator just got replaces and my alternator belt. but as soon as that was done my check engine light went on and now every time i drive my rpms go up to like 5 or 6 and my rear tires start to tick at like 70 mph. Please help me

My car has 140000 miles.
My car has an automatic transmission.

Hello. From what you are explaining it sounds like your issue with the engine rpm is with the idle control valve. Is this engine speed issue only occurs at low speeds then this may have failed, which is common after a voltage issue with the truck. If it occurs at all speeds then you may have a vacuum leak or something else may be disconnected from the alternator replacement. As for the tires feeling like they are jumping that sounds like a tire balance issue. It can be caused by the same problem if there is an air leak in the engine as that can cause the air flow sensor to read improperly which can affect transmission shifting. I would usually start by test driving the vehicle to see when these issues occur. If you are planning on having this engine and tire issue checked, consider YourMechanic, as a certified mechanic can come to you to [diagnose what is causing this fluctuation in engine rpm] https://www.yourmechanic.com/services/car-idle-is-rough-inspection

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