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Q: My truck surges at low and idol speeds. Cold or hot. Sometimes quits when put in gear. Very low speed has a miss.

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I have replaced most sensors and ignition components . Check engine light is not on. If I unplug temp sending unit , service engine light comes on and vehicle stops surging . I've rebuilt throttle body and replaced both injectors . I've changed tps, iac, map, egr , plugs, wires distributer . Also checked for vacuum leaks everywhere that I know to check .

My car has 180000 miles.
My car has an automatic transmission.

A: Hello and thank you for contacting YouMecha...

Hello and thank you for contacting YouMechanic. When you unplug the temperature sending unit the problem goes away but the engine light comes on. Check the plug to the sending unit for any corrosion or debris. Look at the pins to the temperature sending unit and make sure that they are not bent or broken. If the sending unit and harness looks fine then you would need to replace the unit.

I recommend replacing the temperature sending unit and then running the engine. If you need help with diagnosing your Check Engine Light and rough running symptoms, then contact a professional, such as one from YourMechanic. One of our mobile technicians can come to your home to assist you with the necessary repairs.

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