I own a 1990 911C 4. The car is completely restored, engine prof. rebuilt, now with 12.000 mls. I have a problem, when I come to a stop, after driven a few miles, engine idling goes down to about 200 rpm before it comes up to normal 700 rpm, sometimes the engine stalls. I have installed a new hose to the idling valve, because the old one was a little weak, I checked every clip, looked for air intake leaks, none. There is a new K+N airfilter installed, the airflowmeter is working and clean, mileage is excellent. Car runs excellent and smooth. No oilleaks. The oxygen sensor is new, distributors and beltare new, so are the spark plugs, no smoke, car starts right away, even after weeks sitting. Could it be the Motronic? I do appreciate any suggestions. Thank you

 

Remove your idle stabilizer valve and spray it out with carb cleaner. Also, work the valve open with a screwdriver and spray behind the valve out as well. Once it is dry, plug one end of the valve with your hand and try to blow through the other end and make sure you can not blow through it. If you get the valve cleaned out good and can not blow through it, that should cure you problem.

 

Thanks, you are the best. I will do right away. Thank you so much.