318i Convertible

My 1991 318i has developed a stumble (almost like someone turned the ignition off for a second) during acceleration once the engine is at normal temp. I can also feel the same thing on deceleration (something like a miss). Sometimes the engine will continue to stumble and pump fuel into the system causing the catalytic converter to overheat. I have changed the injectors, wires, fuel filter and the fuel pump was installed last year.

Originally Posted by soudafirechief

My 1991 318i has developed a stumble (almost like someone turned the ignition off for a second) during acceleration once the engine is at normal temp. I can also feel the same thing on deceleration (something like a miss). Sometimes the engine will continue to stumble and pump fuel into the system causing the catalytic converter to overheat. I have changed the injectors, wires, fuel filter and the fuel pump was installed last year.

If you are only having the problem at normal operating temperature and not when cold then possibly the Blue temperature sensor is faulty.

This sensor senses engine temperature...not the Brown sensor which activates the temperature gauge.

This sensor....a Thermistor which changes resistance with heat...indicates to the ECU what the engine temp is so that the ECU can vary the fuel mixture accordingly.

It is best to check this sensors' resistance right at the ECU connector....should read about 3,000 Ohms when cold and about 300 Ohms when hot.

You probably have the M42 engine....I think the sensor is located under the intake manifold.


Otherwise check your plugs, plug leads, distributor and coils.