"The Surge" - no, not that one!


#1

we recently exchanged our Subaru Impreza for an '01 Outback (6 cyl. auto trans.) wagon and are very happy with it EXCEPT - we are having to be careful when parking or otherwise just moving the car very slowly. On these occasions the engine surges of its own accord (not a Honda!) so we need to hover over the brake pedal in case the car moves too far… Would appreciate your feedback as to what is the possible cause. Of course, at the Subaru Service Center it didn’t do it!..


#2

It’s possible the tps (throttle position sensor) is producing voltage spikes at, and near, the idle position. The MAF (Mass Air Flow) sensor could, also, cause surge. A sticking iac (idle air control) valve is another suspect. Either sensor’s behavior is easily observed with a scan tool which has a screen (of its own, or when attached to a personal computer). The surge doesn’t have to be happening right then, for the sensor performances to be observed. Ask around for a good independent shop. When you talk to the “receptionist”, he/she is usually a mechanic; or, can call to one just feet away.


#3

thanks,hellokit -will go follow your recommendations and let you know outcome.


#4

The mechanic should, also, put a vacuum gauge on the intake manifold. Low, or varying, vacuum can indicate vacuum leak, and other problems. Unstable fuel pressure/flow is another to check with a fuel pressure gauge.