Q: Pulsing

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I got the truck about 4 months ago it has been doing this since I got it about 2 months ago it had to go into the shop because the pulsing got really bad and my check engine light came on and I couldn't back up without the the stalling it was the camshaft position actuator solenoid, it's still doing the pulsing and shop can figure out what it is. When stopped at a light the entire truck pulses or rocks but if I put it in park or neutral it stops pulsing. Wanna get this figured out and taken care of

This may be a sign of a faulty MAP sensor as the vehicle responds adversely to a load put on the motor (i.e. putting it in gear, turning on AC or engaging the brakes). 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 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 inspect your vehicle.

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