TTownThomas

OK,

I have had an '85 targa for a month. It seems to be developing a new issue. During cold startup (I live in NC so its not that cold yet) the car almost stalls out for the first 30 or so seconds I'm driving. It feels like it is running on 5 cylinders for that time. After 30 seconds or so the car runs fine and seems to run great when it us up to temperature. During a pre purchase inspection a reputable porsche tech (Millersport in Hillsboro NC) I was told that the car has been very well maintained and that Chuck(I think) Miller of millersport knew the car well and he called it a very nice car. He did do a leak-down test and there was under 10% in all but one cylinder. that one was close to 20%. Chuck told me that he felt like the test was an anomaly and based on what he knew about the car he suspected that the one cylinder result was possibly due to the car sitting (PO barely drove it for the last 2 years.) Furthermore he thought that if the test were re-done we would probably get a more consistent result. Anyway I bought the car accordingly knowing there was a possible problem. I would rather there be a simple answer but my My question is:

Does this symptom sound like it could be related to the leak-down results?

What is the best way to diagnose the issue?

Does this sound like it could be anything else "simple"?

Any advice would help

Thanks
Chris Thomas
Cary NC
'85 Targa
'87 951 (Sold)

TTownThomas

it has 81,000 miles on it and I don't think it has had a top end re-build

TTownThomas

Is there something wrong with me if I keep refreshing to see if I have gotten a response yet? I haven't. Urgh.

Chris

rusnak

You might check the CO mixture w the O2 sensor disabled. This is the fuel air mixture controlled by the Air Fuel Meter, prior to the O2 sensor heating up, and entering "closed loop" mode. As an aside, the sytem goes into open loop at full throttle as well.

rusnak

Or, it could be a vacuum leak or maybe the fuel pressure regulator is taking more time to lean out the fuel mixture?

If it were missing really bad, I'm sure Chuck would have told you.

TTownThomas

how do i check the CO mixture? Is this the voltage reading off the o2 sensor?

Erik@GBox

This could be a simple issue of warming the car up prior to driving it. Air cooled engines like a bit of time to warm up and seal themselves a bit before being driven. This will usually take about a minute sometimes two depending on the temp outside.

Do you get any smoke at all on startup? I am not sure what everyone else will have to say about this but it takes my 911 about 3-5 minutes to warmup and really run cleanly.

Just a thought.

Erik Johnson
GBox Sales Manager
(303) 440-8899 work
(303) 895-4828 cell

rusnak

Yes, you can get a very rough estimate from the O2 sensor. A better way is to use a CO meter, or a fuel air meter such as an LM-1 or similar.

At 88K miles, I do not think it's time for a rebuild.

I agree, the 911 will run better after it's warmed up, but it shouldn't stall either. The fact that it runs better after it's warm makes me think it's not the O2 sensor, AFM, or ICV. See if the vacuum line to the fuel pressure regulator is connected. If you haven't yet, you might want to get a Bentley Publishers service manual.

TTownThomas

I have had a little smoke at startup. Especially in the first few days. Since then not so much

chris

TTownThomas

I have had a little smoke at startup. Especially in the first few days. Since then not so much

chris

theiceman

mine starts and settles IMMEDIATELY .. less than 10 seconds ...