rjoconnell

After buying a 93 C4 a year ago and driving it daily with no problems I finally took it to a dealer for a 35k mile service (I got it with 18k on it!). Straightforward and friendly - but as I drove away the engine light came on intermittently for several minutes at a time. Drove 20 miles to work, car very hard to start when I left work later. Idle overshot, oscillated 3-4 times and died whenever car stopped. Checked DME code (I dug this up on the web when I realized there was a problem); it was 1_24 = O2 sensor. Took the car back to the dealer, they reported an open circuit on the sensor (does this mean unconnected?) and replaced the sensor. No charge for labor since I argued that the sensor got screwed up during removal for the valve adjustment, but I was willing to pay for a new sensor. Ten days later after daily 25+25 mile commutes and a 5+5 hour round trip from Boston to Maine, the car was very hard to start one cold evening after work (25 deg F). Idle was completely missing - I had to keep throttle down to keep car from dying. Engine light on. Drove 20 miles on expressway, light went off and idle returned. When I got home I checked the DME code and got 1_22 = idle speed control. Dropped car off at dealer this morning; their diagnosis is to replace air flow sensor (not the error code I saw!) for $800+. I told them to hold off, and contacted an independent mechanic to take it to next week. I will pick up the car tomorrow.

After spending the evening looking over recent posts I have become even more sceptical than I was before. It seems plausible that the idle problem is with the idle microswitch, which failed to close but eventually warmed up or jiggled loose after driving. After the service and oil change I had noted that the oil level was high - the needle was pegged at the top, although the dipstick was right on the top mark, and not noticeably over. Is it possible that it was overfilled and excess oil has caused the idle switch to stick? (not to mention possible effects the airflow sensor).

In any event I would appreciate hearing some other opinions and getting some advice from those more knowlegable and experienced than I am. This is my fourth daily driver, starting with a 356C in 1964, a 1970 911T (the last one to see a dealer in the mid 70s), and a 1979 911SC before I got the 964. All have been solid and reliable, although things have broken and worn out as expected. But this rash of problems immediately after servicing is puzzling. I won't have time to poke around much myself until the weekend.

Thanks for all the info I already found on the list - you all have been doing a great job.!

Rick