Q: 1- Jerk at highway speeds and coolant guage goes crazy when this happens. 2-Truck starts accelerating randomly when idleing.

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When I drive on the highway I experience a jerk that is not a transmission jerk but more like a miss or loss of fuel. When this happens my coolant gauge goes all over the place. Turning off and on as the problem happens. Another problem that started happening at the same time is my truck accelerating when I am idling.

My car has 270000 miles.
My car has an automatic transmission.

Hi There, It sounds like you may have a couple of different issues. The jerking reaction and random acceleration problem is likely related to a dirty or faulty mass air flow sensor. The mass air flow sensor monitors air intake as it is mixed with fuel prior to being injected into the motor. This sensor relays vital information to the ECM which uses this to make adjustments to fuel supply to the motor. A dirty or faulty sensor can cause an imbalanced air/fuel load to be supplied to the motor which results in an over fueling or under fueling situation depending on the conditions. This type of inconsistent fuel supply to the motor may cause a hesitation, loss of power, a jerking reaction, potentially a bit of black exhaust smoke and typically a strong smell of fuel when this sensor is malfunctioning.

The erratic fluctuation of the temperature gauge may suggest you have a bad coolant temperature sensor, which may also be contributing to the random acceleration and missing reaction. When the coolant temperature sensor is not working properly, this can cause the computer to make inaccurate fueling adjustments to enrich or lean out the fuel supply depending on temperature. I would suggest having a professional from Your Mechanic come to your home to diagnose and inspect your vehicle.

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