The car:

1985 T/A with LG4 (170,000 miles)
Hooker 2055s
Full 3" exhaust
High flow cat
Open element
MSD wires, cap, rotor and coil
4* advanced timing
Other than that, essentially stock

The car has just recently (and quite randomly) developed a problem where it will backfiring very badly when I try to accelerate at anywhere from 1/4 to 1/2 full throttle. I haven't changed or touched anything on the engine for a good period of time and this problem has just started happening two or three days ago.

Basically, the car idles fine and will accelerate fine up until about 1500 RPMs, then it will start to sputter and backfires (or at least that is what it sounds like) and it only gets worse with additional load being put on the engine. When I let off the gas, the engine starts working properly again and rides smooth. Although I am trying to baby it right now, it doesn't seem to do it past 2000 RPMs, and when I really step on it, the problem seems to go away to a degree.

Tomorrow I'm going to check the timing and see what it's at, as well as check for any fubared spark plug wires. I checked the spark plugs earlier tonight and none of them are loose as far as I could tell.

Based on these symptoms, what does it sound like the problem is? Other than maybe having the timing way off, I can't think of anything that would cause this. I need some ideas on where to start checking to figure out what is going on.

Thanks for the help.

 

Last year when I was living in Key West FL. rigth after one of the hurricanes my car was doing the same exact thing. I had just done a complete tune up like 4 months before. Well after asking lots of questions racking my brain I did yet another tune up.
Solved the problem too, something with humidity , pressure and gremlins.
Anyway I can live with the mystery and just move on.
I'd check your plugs, cap and all that stuff. Never know.

 

Just throught I'd update this post since I fixed the problem. It ended up being a fouled out spark plug in the #8 cylinder. Don't know exactly what caused that, but I changed out all of the plugs and it's working great once again.

Thanks for your help.