I cut my base timing and fuel pressure back a bit and took the stang over to inspection. It passed easily and my emissions numbers were pretty good. Anyhow, I start heading back home and suddenly I've got what feels like a dead miss, but I couldn't understand why since I replaced the plugs and wires recently. I ran a KOEO test when I got back to the house and the EEC threw a 543 (fuel pump circuit - open connection). Can this be? Would it even run at all if the circuit was open? I went ahead and ran the KOER test and it passed with a 111. I decided to reset the EEC and set my base timing and fuel pressure back to my usual numbers. I fired it back up and went for another spin and it ran fine. Could the lower fuel pressure wreak havoc with the EEC? I ordinarily leave the fuel pressure set for 40# with the vac. hose off, but I cut it down to 35# before I went to inspection. I also retarded the base timing down to 4 deg. BTDC with the spout out. Ordinarily I leave it at 12 deg. BTDC because if I advance it any further I start getting a little pinging under load. The check engine light never came on, but it was really running like a dog on the way back home from inspection.
Not that it's the case here, but it can be a ghost code. Any time the pump loses power for a split second, the FPM can generate the code. Also, stalling the car can create it. Good luck.
I can hear the fuel pump cycle on when I turn the key on (which is normal, of course) so I took another test drive today and it seemed okay. I can't explain what happened yesterday, that was kind of weird.
Until you can recreate the problem I wouldent worry about it. You cant diagnose it anyhow now that its not doing it.
