2002 Lancer OZ Rally EGR Issues
 

2002 Lancer OZ Rally w/41k miles. This is a plague that many Lancer owners have come across but have never solved. The car stalls, idles strange (low/high), surges while driving etc. If the vacuum line on the EGR side of the throttle body is pulled the idle returns to normal for the most part and then starts bogging, hesitating and racing in idle when the steering wheel is turned. All vacuum lines are clear and replaced, New EGR installed and all the sensors/solenoids/switches that go along with it. New IAC, TPS, MAF, MAP, fuel pump, filters, ignition coils and the throttle body was pulled and cleaned. I have the factory service manual and have gone through everything. I know the EGR solenoid is cutting the vacuum as it should around the 2000 RPM mark. I recently had it in a shop because I went through everything and they returned the car free of charge and said, "if you figure out what's going on with this car, please let us know because none of it makes sense." My theory at this point that it is a computer gremlin. The only thing that has not been gone through thoroughly is the PCM or a drive with a computer reader running.