Car Backfiring


#1

I have a 1990 pontiac firebird 305 tpi. It is backfiring out the exhaust. I have change the plugs, wires, distributer cap & rotor, added injector cleaner. It has a new remanufactored ecm unit. Im stuck! can anybody help? ~ Kurt ~


#2

Have you checked the timing?


#3

Yes, 6 degrees


#4

yes, 6 degrees


#5

Are you sure the plug wires didn’t get crossed somewhere?


#6

Did it run right before you worked on it?


#7

Did you check the ignition timing with the test connector grounded though?
Backfiring out the exhaust may mean the timing is retarded too much.


#8

Good point. I looked up the procedure for putting it in base timing and the procedures are different for a engine with a carb and a fuel injected engine.


#9

Yes, I did check the timing by disconnecting the timing advance wire. I was reading in the chiltons hand book about the emissions air pump diverter and valve. what do you think about that? could that be a possability?