I have a pair of '99 502 MPI's in a Formula 400ss and the port engine has a hard start problem when cold. It cranks over / starts / and then stalls anywhere from 4 or 5 up to maybe 10 times before it will finally stay running. First thing I checked is fuel pressure and it makes and holds 42 psi as soon as the pump primes before starting. Once the engine starts and is idling it has about 38 psi. Possible other clue is that once it does start it sounds like the IAC is wide open and then slowly closes over the course of around 10 seconds but I chalked that up to the IAC trying to compensate for the numerous stalls? Still I'm thinking maybe an IAC problem? Someone suggested TPS also? It acts like a fuel pressure or vapor lock problem but it's not hot (like it would be to cause vapor lock) and has good fuel presure. I'm getting a guy to come down with a scanner to look at real time data but figured I'd ask here if anyone has experienced this problem?

Thanks, Pat

I would definitely lean towards IAC. If it is sticky it may not be able to open quickly enough to keep the engine running. You will be able to tell by the IAC counts if you watch it on a scanner.

i would lean towards the water temp sensor if it is reading hot then the computer already thinks the engine is up to operating temp

Thanks for the replys

Ted,
I was also thinking IAC but don't have a scanner to read any data on these engines. I'm waiting at the boat now for the Merc guy that's coming down with one

Ed,
Interesting idea with the coolant temp sensor. That might make sense that it's trying to start on too lean a mixture if the ECU thinks the engine is already warm and then it finally starts after getting enough fuel from the failed attempts to get it lit. I'll check that out also.

Thanks again, Pat

A scanner should allow you to monitor both things, and should get you fixed. Ed's idea is a good one also.