964 DME Problems-Air flow sensor?
 

Anyone with a C2/C4 (964) ever had problems with their air flow sensor or oxygen sensor?

My 1993 RS Am has developed a problem with the DME system which the Hammer has diagnosed as having both those components coming up with fault codes. My car only had 10000 miles when it inexplicably stalled and loss power. Was hard to restart, then have intermittent moments of perfect running then re-exhibiting the above problems.

Checked the ground points under the car and they are pristine.:(

A friend of mine who (oddly enough) also has a '93 RS America, had to replace his airflow meter. It had around 65K on it though.

The oxygen sensor code is probably nothing, since they almost always set that code whenever the fuel mixture is off. So, tha fualty airfow meter probably caused the O2 sensor code as well. Ignore that code. Your O2 sensor is likely fine.

I took a look at the sensor by removing the air filter and pushed the flap gently to see if there was any problems. It moved easily and there appears to be spring tension (so no broken spring or gritty obstruction, nor any oil from over-filling-regurgitation into the air box area!). I was not able to find any signs of dirt , corrosion, or problems with the sensor. Again the test drive did not produce any faults or poor running for 20 miles driven. Idle is normal. The only difference was replacement of the DME relay with the 944 part# with the later 993part# one. The old relay appears undamage and did not have any rattles when shaken.

So who knows what the problem is (have replaced the O2 Sensor at 11,500 miles so that definitely is not the root cause of the problem).

Did find a loose bolt (allen head bolt 3 maybe 4 mm allen wrench will fit about 30 mm long with fine thread pitch) on the engine tray under the oil filter region of the engine. CANNOT find matching HOLE it fell out of- if it was ever screwed into the engine manifold or accessories in that part of the engine area.

I suspect this bolt may be rattling and that sound may have been picked up by the knock sensor to cause a retardation of ignition timing?? (Anyone care to voice their feelings about this?) Where is the location of the knock sensors in a 964? (Is it at the end of the intake valve covers and look like a right angled aluminum tube or is this an oil fitting?

Final Solution
 

I finally decided to spend $500 to replace the sensor unit. Installation was easily accomplished (even with a bruised thumb 1 h before attempt, slammed my wife's honda's door on my self without paying attention). The car is running 100% normal for the last two trips so far and no more codes!
My wife gave me the new sensor as my anniverary gift. So thanks to her generosity all is well.
One more item needed is a paper gasket ($2) which the dealers never seem to stock and costs really $20 more for fedex fee!

It's great to have a Happy Thanksgiving when your favorite car is working well again.SmileWavy