rjr

My motors were pulled last year. After re installation one backfires around 2500 - 3500 RPM. I have replaced the throttle position indicator, checked firing order, checked for codes (none), swapped MAP sensors. Compression check is next. Can anybody think of anything else?

Ted G

iTrader: (1)

Check fuel pressure when it does it, backfiring can be due to lean mixture.

rjr

Thanks for the input, I seem to recall that the fuel pressure was OK but I will double check. I don't think its fuel related though because it runs fine WOT.

Ted G

iTrader: (1)

Have you got a good cap, rotor, and plug wires on them? At 2500-3500 you are pulling "over the hump" so any lean condition or loss/scatter of spark will be magnified at that point.

SVL-WARLOCK

Pull the cap and lock tite the rotor. should fix the problem

rjr

Thanks, I will try that and let you know.

rjr

Problem turned out to be the fuel pump and pressure regulator. They were both working well enough to run great at idle & WOT, but not well enough to run when the load got high either coming up on plane or when I backed off a little. Which seems to indicate that the best fuel economy is somewhere over 40 MPH.

jmoore1225

iTrader: (1)

My 502 efi developed shutting off this past weekend @ 4000 rpm.... I could run 3900 all day, as soon as I hit 4g's It would shut off... If I backed out fast enough & pumped the throttle about halfway I could save it from stalling sometimes, fuel related? But any ideas where to begin?

mookymonkey

fuel pressure problem for sure. had the same issues about a month ago...