Originally Posted by BigRed1781
So here's the deal, my brother in law has a 87 gt. It started bogging out in the upper rpm's & when he would let off the throttle it would after fire (kind of like a backfire but through the exhaust) but only when hard on the throttle. If he eases into the throttle it would stil bog down in the higher range but no after fire. First we checked the plugs & wires, we discovered that the #1 & #4 plug wires were switched. We put them in the proper places & it ran better but stil did the same thing. We tried adjusting the dizzy & the problem got a little better but stil was there. Next we checked where the rotor was in relation to TDC on #1 cylinder and the cap. It was off just a hair. We pulled the dizzy & lined it up perfect with #1 on the cap & it wouldn't even start. So we put the dizzy back where it was, 1 tooth past the #1 on the cap & it runs just like it did before. With it being off we are running out of adjustment when turning the dizzy. We also changed the coil 3 times. The only thing I could think of is maybe the pickup in the dizzy is bad, or it's a fuel issue. The reason I say a fuel issue is because after it starts running funny it smells really rich. I'm thought I would turn to the pros on this. Any ideas would be greatly appreciated. Thank you
Ok, first I would get a timing light and set base timing at 10 degrees with the spout connector removed. The bogging and back firing could be due to fouled plugs, wires grounding out, or the fuel pressure regulator is possibly bad.
The fuel pump may also be having problems, I would find a fuel gauge and check pressure as well. It should be around 35psi at idle and 40+ at wot.