Have them ck the cooler lines at the radiator, the clamps do come loose and leak. The surge or buck could be a 02 sensor or a missfire. Ck the front of the motor and see if you have a knock sensor. If it does unplug it. this also give you a misfire at times too. There is a TSB to remove the sensor.
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Master Chassis tech, Transmission
Automatic and Manual and Suspensions.
Also repair front and rear diffs and all engine
repairs inc Diesel. A/C repair too.
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