Cold start: Engine starts but then cuts out

Hi all, Looking for any advice for my 987.1 S. Last week it developed an issue with cold starts. The car is 100% fine when running, but at tick over and at load. The issue is that it will start and run for 1-2 seconds before dying in cold whether 0-5 degrees C (in Switzerland). The time it runs for is very regular before cutting out (no variability). Giving it gas pedal doesn’t help the issue. Is there a cold start process that changes the fuelling 1-2 seconds after startup? I’ve bought a fuel pressure gage, which I will hook up later this week. I’m hoping it’s not the expensive high pressure fuel pump , but from reading the forums, seems like potentially some sort of fuelling issue. Anyone has something similar? Thanks for any advice!!! Matt

Are you sure you even have a high pressure fuel pump ? I thought that was only for the later generation direct injection motors (starting with the 987.2 S models). As far as your problem, I’m not going to be much help, but most cars do have a cold start cycle where more air and fuel are added (typically idling around 1000rpm). Older cars I am familiar with had an air valve that bypassed the throttle body to let more air in. If that malfunctioned, it typically wouldn’t cause the car to stall, and either way, I bet the Porsche handles it differently, anyway. You basically need correct spark, fuel, and air. How fresh Are your ignition components? Is the MAF working correctly/no vacuum leaks? Sounds like you are on the fuel pump diagnosis path for that part of the combustion triangle… I’m sure people with more deep knowledge of the 987.1 engine system will chime in, too. I was in Switzerland just a bit ago. Beautiful country. Expensive, but nice. 🇨🇭

Thanks for taking the time to reply! This is already helpful. I didn't know that the 1st gen cars were port rather than direct injection. The engine was re-built at Hartech in the UK 4 years (15k miles) ago, which included new plugs and coils at that time. I checked the car with a generic OBD plugin (non- Porsche specific unfortunately) which shows no faults. Everything looks normal apart from one O2 sensor reading, which looks unusually low. I had a listen for vacuum leaks but couldn't find anything obvious. I could try with soapy water / smoke as a next step. I will try unplugging the MAF and see if that makes any difference. I'll also give it a clean. The car definitely gets a little oil in the air intake box (I understand that this is quite normal if driven hard, and it does get occasionally driven on track), and I imagine that any oil vapors can be bad for the MAF. Switzerland is indeed a beautiful country. I did a trip over some of the mountain passes on my motorbike last year and would like to do the same in the car when they're clear of snow (probs end of June for the high passes). Cheers! Matt

Propane torch. DO NOT LIGHT IT. Just open the gas up and run it slowly along the vacuum lines. You will hear the engine speed up if you have a leak. Again. DO NOT LIGHT IT

Thanks Ric_in_RVA! I'll have to check if I have a propane torch Message understood -DO NOT LIGHT IT! So... I got the fuel pressure tester on the car today. Results: 2.6 bar before turning on the ignition - seems OK from what I can see - above 2 bar. 3.3 bar when ignition turned on - seems low. If I've got the right info, seems like it should be 3.8 bar. 3.6 bar when cranking and idling - seems about right, if not slightly high. 0.5 bar lower pressure than expected when the ignition is turned on before cranking. Need a new fuel pump ? Any advice appreciated! Matt

The comment about 1 of the O2 sensors drew my attention. There is a warmup phase for the O2 sensor , and I think the O2 value is ignored for a short time to allow preheating and warmup from the exhaust . The car could be stalling when the O2 sensor kicks in resulting in a change to the fuel mix. But you didn't see any faults related to the O2 sensor ? Was the sensor before or after the cat?

Hi Bobp, thanks for the suggestion. I was wondering something similar. I'll have to check on the App that i was using ( OBD Fusion) to see which side and whether it's a pre or post cat sensor. No faults, i just remember seeing the low reading on one side not consistently matching the other. I took off and cleaned the MAF yesterday. They don't make it an easy car to work on. Access was less than ideal, but I guess that's what you put up with for a mid-engined car!

Did cleaning the MAF help?