Q: My car is trying to stall when shifting gears.

asked by on January 17, 2017

My vehicle is a manual and you could be running along at 40 mph and brake and down shift to 2nd in t turn as you start to leave out of your turn it will start bucking like it is under fuel but you have your foot on the gas and then it will buck like it is going to stall so you down shift to first to bang up the rpm's and then re shift to 2nd and sometimes it works and sometimes it doesnt and you have to repeat the process. This is with all gears but first. So 3rd to 2nd , 2nd to 3rd, 3rd to 4th, 4th to 3rd and so on. It seems like it is going to back fire or stall if you keep pushing it so I shift out of the situation, usually down trying to get the rpms back up. Then there are times you drive it and it doesnt do this at all. It almost seems to act up like this after you take a turn at 15 or 20 mph like something is loose maybe. I am completely lost. This is my daily driver and I am worried the whole bottom is just going to fall out on me. I am a vetran of the Gulf and need help please

My car has 120345 miles.
My car has a manual transmission.

Hi There, It sounds like you may have a faulty MAP sensor as your vehicle seems to respond adversely to varying loads being placed on the motor which is what the MAP sensor is designed to do. 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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