Weird engine issues upon cold start... - 986 Forum - The Community for Porsche Boxster & Cayman Owners

papasmurf · 11-09-2010, 08:09 AM

I have a 2000 2.7 with 60k miles. I do pretty much everything I can on it myself (AOS, motormount, oil at 5k intervals, etc.) and have had this problem for quite some time and would really like to find some sort of solution without having to travel to a dealer (couple hours away). There is one independent shop where I live that services european cars and porsche and I took the car there a little less than a year ago and was far from pleased with the work they did. My issue is that the car runs poorly with the clutch pressed in when it is cold. Upon startup the car runs fine while the air injection pump is going. After about two minutes of the pump running it shuts off and the idle drops to 900 or so while the car continues to warm. The idle is steady and you can gently rev the engine (1200-1500 rpm's) without issue. If you press the clutch and do this (as if to leave from a standstill) the engine will change tone and the rpm's will drop like it is bogging down. You can hold the rpm's steady at 1400 and barely press in the clutch pedal and listen to it bog down and the rpm's drop. If you hold the throttle input steady the rpm's will return to normal after a couple of seconds like it is adjusting the mixture. It used to "spit and sputter" and I changed the MAF sensor about 10 months ago and it got alot better but the bogging is still there. There is a distinct change in the tone of the engine as it seems the mixture is changing and the car may be leaning out I assume when the clutch is pressed in. I have asked this same question on several forums and no one knows for sure. Before I took the car in last year I was getting codes 1128 and 1130 (o2 sensor enrichment limit). After changing the MAF the codes never came back. I know at 60k the o2 sensors could possibly need changing but I do not want to guess at the problem and see if that works. Once the car warms up, it seems to run fine and the bogging symptoms just past idle do not seem to persist to the extent as when the car is cold. The shop I took it to thought the AOS was bad even though I had replaced it a year earlier and it only had about 10k miles on it (~20k miles currently). They wanted to replace the AOS and go from there to possibly the MAF. The guessing they were doing I did not appreciate and I felt if they could not determine within reasonable doubt the problem, they should tell me so and let me go elsewhere. I had them do a smoke test on the car to check for intake leaks and they said they found none. I am going to try and get a video of the car one morning when I first start it so people can hear it and see what it is doing. I have tried to contemplate how the clutch is intertwined with this hesitation problem and it still baffles me. If there a way to test the performance of the o2 sensor while they are in the car. I know with my 300zx the dealer could plug in a diagnostic computer and check the performance of the sensors. I have an actron OBD II scanner but I do not think it can do much beyond read the basic codes...hoping to find a durametric soon!

Bladecutter · 11-09-2010, 08:55 AM

I hate to point out the obvious, but have you considered that it might actually be a clutch related issue?

Since it only happens when you push in the clutch pedal, I would have to make the assumption that something is wrong with the clutch, pressure plate, flywheel, or the bits that connect them all together.

BC.

extanker · 11-09-2010, 10:42 AM

i think a good scan tool ,not a code reader,should be able to show what is changing when you step on the clutch ...strange one indeed...keep us informed

Steve Tinker · 11-09-2010, 02:21 PM

Apart from a mechanical clutch issue being the problem (which I can't see as the clutch / gearbox is being "disconnected" from the engine when the pedal is pushed), the only electrical connection to the DME would be the clutch switch which is fitted as standard (I think) in the US (but we don't have it here in Australia).
I would try bridging out the switch and see if the fault persists.
Please keep us informed......

papasmurf · 11-09-2010, 05:11 PM

I assume this is the same switch that will not allow you to start the car without the clutch pedal pressed?

Steve Tinker · 11-09-2010, 08:45 PM

Correct.
As we don't have these switches fitted to Australian delivered cars, its difficult for me to technically appraise it, but I would imagine that it is a 2 wire switch mounted adjacent to the clutch pedal. It will have a toggle that either pushes in or springs out when the clutch pedal is actuated.
Make sure the toggle operates correctly by disconnecting the wires and putting a multimeter across the terminals to see if it is switching.
I'm sure somebody on here can tell you if you either A) disconnect the 2 wires permanently or B) connect them together permanantly to bypass the switch.

papasmurf · 11-10-2010, 05:27 AM

this morning when I started the car. I'll try to get it posted at lunch if I can.