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

 

That seems about right with the fuel pressure at idle, 32-38 is normal. I know that engine backfire can sometimes be caused by a dirty fuel filter, but I think that also affects fuel pressure?

 

Thanks Canary, I'll change the filter and see what happens. Any other ideas out there?