Q: Car starts bucking/jerking when letting off gas on the highway

asked by on October 22, 2016

This started not too long ago, it only occurs at high speeds. I noticed it occurs after 60mph. When i push the gas peddle, it drives fine, it doesn't jerk or anything. But when i let go of the gas, the car has a sudden jerk as if its gonna turn off or something. I would think its a motor mount, but then this problem doesn't occur in the city, only on the highway at higher speeds. I changed the transmission fluid, the transmission shifts fine. My car doesn't have over-drive. Its a 2006 suzuki forenza 2.0. And i dont have check engine light. Although when i did the motor mount test. The motor moves forward about 2 inches in reverse with the brake peddle held and gas pushed to 2000 rpm. and i checker the sparks and the wires and the coil pack, they seemed fine, i replaced them 6 months ago, and it is oem spark plug. Im thinking fuel injectors?although i checked them and they tick just fine. please help me

This is very likely a throttle issue. There is an idle control module (or similar setup depending on your make and model) that is located on the throttle body which helps the gas regulation during these moments. Otherwise, without a regulator, the car performs much like you are describing. There are several sensors, wiring harnesses, and the module itself that can fail. It is likely a code scan will detect some of these issues. Start by having the vehicle scanned for diagnostic troubleshooting codes. If this doesn’t give you any information, then you should look into replacing the idle control module.

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