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Paul R
08-12-2015, 12:51 PM
To begin, I am running a 4.6 DOHC EFI Factory engine from a 1996 Cobra. When I was "go carting" it around, I never had any troubles. Engine ran fine and never died on me. I did not make any changes since that time. I ended up having to wait about 8 weeks before getting the body back on. During that time, I drove the car once and found no problems with the engine.

Now, the car will start and run perfectly all day long.....from a cold start. I have hydroboost brakes and steering. When a load is put on the engine like brakes and the engine is in idle, it wants to die and will die if I am not careful. Then, it will not restart until the engine has cooled down. Same thing happens if I shut the engine off, it will not start. Yesterday I had the engine up to about 150 Deg F when I shut it off...no restart.

I have found that if I give it some gas or pump the gas pedal, I can make it eventually start. It may take 20 seconds to get it to fire up though.

So far, all I have replaced is the fuel pressure regulator. That did not fix the problem. I have good vacuum on the regulator as well. I added premium fuel and fuel cleaner b-12. I am almost positive it is not vapor lock, as I hear the pump cycling back into the tank. I also do not have air coming out of the pressure valve on the rail. And it is not likely for EFI to have vapor lock anyways. But it does act like it has vapor lock.

A couple of other notes: new fuel sending unit, new plugs, wires, distributor blocks prior to problems.

ANY THOUGHTS would be greatly appreciated.

walt mckenna
08-12-2015, 03:03 PM
My first thought is the IAC (Idle Air Control) valve. Mine is located right next to the throttle position sensor on the intake manifold. Before spending money on a new one, I would remove and give it a soaking in carburetor cleaner.

Buzz Skyline
08-12-2015, 04:24 PM
Just a guess, but is there a vent on your gas tank? If it's creating a vacuum in the tank, it might act like that. It's a shot in the dark, but I'd try running it with the fuel filler cap off or loosened.

Paul R
08-12-2015, 06:37 PM
I will try both and report back. Thanks.

Paul R
08-12-2015, 10:35 PM
Ok. I almost hate to admit how stupid I feel right now. When I made my gasket for the iac I failed to cut the holes in it for the air flow. It works great now!! It was really trying to work. Thanks for the help.