94 Q45 stalls when warm and re-started

[stellatariche]

Hi,

I have a '94 Q45, 123,000 miles.

If it is cold, it starts and idles fine.

If it is warm, it starts, but the idle falls so low (in Park) it stalls.

If I put it in gear (when starting warm - foot on brake and other foot on gas to keep RPMs above 2000) it doesn't stall.

If I let it run at 2000+ RPM for 10 secs or so in Park, it will idle fine.

Replaced the fuel pump 15k miles ago. Replace the MAF around the same time.

Anyone have any ideas?

Thanks!

[DAEDALUS]

Could still be a fuel delivery issue. Measure the fuel pressure to be sure. Why did you replace the pump? Did you use an OEM part? Perhaps the controller is on the way out.

[PoorManQ45]

Replace fuel filter...

Adjust IAC.

*edit* The stalling could be caused by a vacuum leak

[stellatariche]

Vacuum leak! Great idea!

I once put a Holley throttle body EFI kit into a batmobile replica (ford 460), and this kind of problem would have been caused by either a vacuum leak or an incorrect value in the ECU.

I don't think it is a fuel problem because it is only under these specific conditions.

So, where should I start looking for a vacuum leak......

Thanks for the help.

[Jesda]

I have this problem every once in a while. I've given up on diagnosing it.

[DAEDALUS]

I don't think it is a fuel problem because it is only under these specific conditions.

And a vacuum leak would be because why? Vacuum leaks can cause hunting and surging in MAF systems. The Q is not a primitive, carbureted dinosaur from the '60s. A vacuum leak can occur at any of the portsand seals between the butterfly plate in the throttle body and where the runners mate to the heads.