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Q: While driving my engine stutters and tries to cut out at 4000 rpm.

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Have no other issues than cutting out at 4000 rpm...just started about an hour ago.

My car has 183000 miles.
My car has an automatic transmission.

A: Hi there. The engine is cutting out for a ...

Hi there. The engine is cutting out for a high back pressure build up in the exhaust system. The catalytic converter or muffler could be plugged up causing the engine to create too much back pressure and when the engine is running at 4,000 rpm’s, the pressure could be too high. Check the exhaust at idle with something covering the pipe and again at 4,000 rpm’s and see if the pressure drops or stays the same. If you need further assistance with your engine stalling out at 4,000 rpm’s, then seek out a professional, such as one from Your Mechanic, to help you.

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A: This may be a sign of a faulty MAP sensor. ...

This may be a sign of a faulty MAP sensor. The Manifold Absolute Pressure (MAP) sensor senses engine load and 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 takes 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 and replace your MAP sensor.

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