I just recently did a compression test on my 1985 5.0 and everything went according to plan. After I replaced the autolite spark plugs with double platinum autolite plugs, I reconnected the fuel line and the spark plug wires. I'm pretty sure the spark plug wires are in the right order. The car will turn over and stay runnig at idle but as soon as I give it a quick push on the gas it backfires and makes a pop noise. Are the spark plugs at the wrong heat? Or should I just redo the spark plug wires one by one?

 

For HO 5.0L (Mustangs), firing order is 1-3-7-2-6-5-4-8. For non-HO 5.0L (all cars/trucks other than the Mustang), firing order is 1-5-4-2-6-3-7-8.


did ya happen to throw ya old plugs or wires back on yet wires not touching and arking on the heads etc.

 

Yeah Probably The firing order... did you label which Plug wire goes where? Whats probably happening, is at idle, you might have 6 out of 8 cylinders firing when they should, hence carrying the other 2 cylinders. The valves are opening and closing so slowly, that the plugs might be firing while they are open, but not enough to cause a backfire because say, the exhaust valve, is staying open long enough to lean out the mixture to the point where it woudlnt ignite, but with the increased amount of fuel plus shorter valve opening time when you go to rev the engine, you do in fact get the backfire. Kinda hard to type what Im thinkin here. Maybe you see what I mean, or maybe Im just rambling like a tard. All in all, check to see your plug wires are put where they whould be.

The heat of the plug wouldnt cause this. The heat of the plug controls how well the mixture burns and the cylinder temp, that kinda thing.

Jim

 

been there, def. wrong order

 

i'm not sure about the non-HO setup he's got there... but make sure if u do the HO order, that you do that counterclockwise starting with 1.