puzzling problem

[tugalo]

Gentlemen of the forum,

 

I have a problem that has me stumped. 88 MJ, 4.0, B/A 10 tranny. The truck has a new short block installed and when it runs, it runs great. When it is in the transition from open to closed loop and I come to a stop, the idle drops sharply and the truck dies. It will not restart right away unless I am in a place where i can roll it off and pop the clutch, then it starts instantly. If I try to start it with the key, it does not want to start at all. After it sits for a few minutes, it will start and then run fine for the rest of the day.

If I feather the throttle when coming to a stop, and keep the RPM's up to around 1200 or so, it doesn't die.

I have swapped out the IAC and the MAP, and cleaned the throttle body. i have tried running it with the O2 sensor unplugged.......no difference. when I pop the clutch and roll start it, the idle goes to 3000 and stays there for quite a while.

 

When it died today, I checked the spark from the coil and it was strong, so in my mind, it is a fuel issue. Any thoughts or suggestions appreciated.

 

Pulled the plugs this afternoon and re-gapped them. They were all light gray with a little brown on the electrodes. Maybe running a bit lean. 4 hole mustang injectors.