mbean

Our 95 993 has had an ongoing starting issue when it sits outside on hot (90+ degrees) days. It feels like vapor lock. The first time it had a whooshing sound when I opened the gas tank cap. We had the charcoal canister/purge valve replaced. It previously had a new fuel pump as well. I haven't heard the whooshing sound lately. A recent 90,000 mile tune up including coils (except for new spark plug wires) made things somewhat better but it still has problems starting when it's really hot outside. As we live in Maine that doesn't happen very often but I would like to resolve it. It starts very poorly and runs erratically for quite a while: you can barely drive it until it clears out. Once I did keep running it and it finally ran better but usually we don't run the car when it's hot. Other than that it runs wonderfully.
The 924 turbo I'm working on had the notorious hit start issue. Looking to replace the check valve in that car. Could it be the same issue in the 993?

Knight

The other 2 possibilities are the Fuel Pressure Reg and the injectors themselves.

I've had warm start issues before and recently just resolve one being the FPR a few weeks ago.
Previously it was the injectors that would act up under certain running temps. Unfortunately the only way to test is to pull them out and take to shop for testing.

Do you have access to a pressure gauge, this would be initial steps to measure the difference when hot vs cold.

95_993

I second the suggestion that it's a faulty diaphragm in the fuel pressure regulator leading to a rich condition on hot start up based on your comment about "cleaning up" its running.

Another possible thing is the DME starting to go and becomes faulty when hot. I am doubtful, but it's so easy to check with a jumper or DME swap.

IainM

Could be a temp sensor, there’s several of them. Could be as simple as a bad connector. I’d ohm out the sensors and make/break the connectors a few times as a no cost test.
do you have a code reader?

911F1

Any fault codes? I had a cylinder temp sensor go bad. It made the car hard to start and it would sputter then die. Tough to keep it running.
My 95 threw a fault code. Thats how I knew. Just a thought. Good luck in your repair.

mbean

The sensor was replaced already and also the relay. FPR?

95_993

That's my vote. 20-30min job. Pretty easy to get to once you remove the blower.

IainM

Check the vacuum lines while you’re in there