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Q: Misses under load

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I got a 97 k1500 with the 5.7 spider injection system. When it's at operating temp (a little below 200), when it idles in drive or reverse (550rpm) it has a miss in one of the cylinders, but when you give it gas and the rpms go up it will run fine, until you hit overdrive. When your on overdrive and you hit the gas it will miss until you give it enough gas to reach 2000rpm. I did a tuneup (cap plugs rotor wires) checked all the gapping and it was correct, checked all the wires to see if they were connected correctly and they were correct. Installed a new fuel filter as well? Any ideas before I start to throw more money at it?

My car has 152000 miles My car has an automatic transmission.

Hello, I would recommend checking the MAP sensor as it sounds like the truck responds poorly to a load being placed on the motor. 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]((https://www.yourmechanic.com/services/manifold-absolute-pressure-sensor-map-sensor-replacement), 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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