Help with friends car
 

My friend has an 1990 Audi. It has a problem, when slowing down it starts to stall and almost cut off. When accelrating it chuggs and struggles then stops around 30km. He did a full igniton tune up (spk plugs, wires, cap rotor) and it is still happening. The coolant light comes on and the gauge goes up high, then the car chuggs and it comes down and the light comes off. Can anyone shed some light on what is wrong with the car and how to fix it? Thanks.

Sounds like a temp sensor to me.

Sounds like a loose wire connection on the coolant temperature sensor, or the sensor is gone.

coolant temp sensor/water temp sensor, there's like 3 I believe. Happened to me on my car and I replaced it, no more chugging.

My Miata had 2. 1 was for the gauge, and 1 went to the ECU. Obviously, it was the ECU one that went and I had the same symptoms.

I also bled the cooling system at the same time. An air pocket around the sensor could cause the same symptoms.