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Q: Rough idle when in drive..but idle is fine when in nuetral or park

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Truck idle is rough when in drive with no acceleration (stop signs, red lights, traffic) but idle is fine when in park or nuetral. . Check engine light just started flashing recently

Hi there. Check for vacuum leaks on the engine. A small leak will cause the engine to stumble when the rpm’s are low, like in gear on automatic transmissions. Look around the intake manifold for the gaskets being broken. Check all of the vacuum lines for any signs of leakage with loose ends or cracks in the tubing. If you need further assistance with your engine running rough only at a stopped position with the transmission in drive, then seek out a professional, such as one from Your Mechanic, to help you.

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