[pzwerner]

About a month ago (52,000 ml) I had the belts chanded on my "93 968 Tip. At the time I had the oil press sender replaced also. The car was running great with no issues.(other than slight vibration at idle--motor mounts ! ). After the car was returned, I had a slight stumbe at the first start-up of the day. The engine fell like it was hunting for 3-5 secs, then run as normal. I would not have the problem the rest of the day.( 2-3 start-ups). My shop kept the car overnight when it was back for bs belt retension, but they found no hesitation on start-up in the morning. Races are over now until SCCA Runoffs next month, so I'm planning on taking it back to them. I'd like to have some info on what to look for. The timing seems off to me, but they said they rechecked it . Also, my wife went with me up to a race in Michigan two weeks ago and we took her Sienna. On Mon., after not driving the Porsche for four days, I noticed a knock on startup. It lasted about 2-3 sec. and I have not heard it since. The mistakenly changed oil/filter when it was in, but said they replaced with Mahle and Mobil 1. I'v driven Porsches for the last 35+ yrs, so I try to keep my cars as well maintained as possible. I lost the cam chain on an S2, so I KNOW the problems poor maintainance can produce. Any help and info is greatly appreciated.....



Paul Zwerner

pzwerner@netscape.net

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[S_Cal968]

If this issue only occurs on start-up I would suspect that there's a questionable sensor. If the DME is not getting the correct parameter from all the sensors, it'll vary the idle [hunt] to compensate for the anomaly. Most engine electronic systems have a start mode and a run mode [open & closed loop] and the parameter requirements are different for each.

If it was a timing belt issue, it would be experienced all the time.

Unfortunately start-up issues are the hardest to troubleshoot because they don't always set a trouble code. However just for the heck of it, I'd suggest checking for any stored codes.

I would guess that a sensor [brittle connector?] was disturbed during service.

Good luck...

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[flash]

have you looked at the plugs?

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