Fatboy

Hey guys,
I need some help. I have a 69 with a bone stock 88 5.0 and AOD. The motor has been in the car since 95. It was running fine, but I sat it up for about 8 months and now it backfires through the intake when under load. If I'm in any gear at an idle and I attempt to accelerate, it pops. If I nail it, it runs fine. It's only when the engine is loaded up at low RPMs. I got rid of all the old gas and put a full tank of premium with some fuel injector cleaner in it. That didn't help. I checked the fuel pressure and at idle I have 35 psi. When I rev it, it goes to 45. Is that about right? I think it's because the motor is lean, but I don't know why. I haven't checked the timing yet, but I can't see any reason why it should have changed for no reason. Oh yeah, the wiring harness I have doesn't have an OBD connection so I can't get any codes. Anyone have any suggestions?
Thanks

Nav50

Sounds like timing

mattdel

my main suggestion, gonna need to check your MAF, and you're gonna need an oscilloscope.

secondly, after sitting 8 months, all kinds of critters can find their way in. Mice like to build nests in wiring. Have yourself a thorough look through.

mjr46

....if it was fine when he put it away 99% of the time it won't be the timing as sitting explain how it'll of moved?? exactly..it doesn't.....since the car has sat for a extended period of time, I'd more so suspect, cap, rotor or wires