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Q: P0068? Runs rough and idles high

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Runs but idles high and kinda rough

My car has 180000 miles.
My car has an automatic transmission.

A: Hey there. This may be a sign of a faulty M...

Hey there. This may be a sign of a faulty MAP sensor. The Manifold Absolute Pressure (MAP) sensor is a key sensor because it senses engine load. The sensor generates a signal that is proportional to the amount of vacuum in the intake manifold.

The engine computer then uses this information to adjust ignition timing and fuel enrichment. When the engine is working hard, intake vacuum drops as the throttle opens wide. The engine sucks in more air, which requires more fuel to keep the air/fuel ratio in balance. When the computer reads a heavy load signal from the MAP sensor, it adjusts the fuel mixture to slightly more rich than normal so the engine can produce more power.

The computer will then retard (back off) ignition timing slightly to prevent detonation (spark knock) that can damage the engine and decrease performance. This may also be caused by other closely related components such as a dirty or failing mass air-flow sensor, a faulty throttle position sensor, or potentially a vacuum leak. I would recommend having an expert from YourMechanic come to your location to diagnose the rough idle and follow through with correct repairs.

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