my 85 is backfiring through exaust. it has all new sensors, injectors, plugs, wires, coil, egr valve, knock sensor, tps, os, dis cap, rotor and button, fuel filter. i have not checked the fuel pressure cause i dont yet have a guage. i did find a vac leak at the regulator and it runs sooo much better but its backfiring through the exaust. i have searched all archives but didnt come up with anything. also no codes. jumped the fuel pump relay and hear a continous noise like its pumping fuel somewhere but i dont see any anywhere. someone on here told me to change the ign module when changing the coil. is this a sign of it going bad? or maybe the fuel pump? i think from what ive readif its lacking fuel it will run lean wich will cause it to backfire through the intake? its def coming out of the exaust (straight headers with collectors) i can see it popping there. any help from the experts will be appreciated. i was getting very discouraged with this car untill i joined this forum and found alot of people know these cars!! and alot of ignorant people like me. but im learning!! thanx guys

 

Check and recheck plug wires has not crossed. 1-8-4-3-6-5-7-2 firing order, another cause might be too much timing advanced. But most likely wires crossed.
Did u replace ign module too? if yes than did u use silicone paste it came with?
have TPS set at .54 volt/ 4.0 or greater at wot?

Did the plug wires snapped at plugs tight? did u hear clicked sound.
Is the plugs gapped accordingly i set mine at .035.

just check and recheck these basic things.

 

also: if you removed the runners/plenum, if the gaskets and bolts are not torqued on the runners to manifold and plenum, you can also have backfire and hard starting...

 

i did not replace ign module. do i need to? plugs and wires are good i put accel 8mm wires they are snapped. ac delco plugs gap checked good. tps is right. i had the pelinum off and didnt change the gaskets but its tourqed right