I'm getting these backfires all of a sudden. It happened after I took my car for emissions. We had to jumpstart it at least 10 times to keep it running but it passed. On my way home though it started backfiring. I check the plugs, wires, cap, rotor, etc no problems. I think the jumpstarting messed up either the computer or the ignition module (both are the original ones with 125k on them). The strange thing is if I unplug the brown ground wire (like to set the timing) it doesn't backfire at all, runs great. So should I spend the $225 for a new computer or $75 for a new IM?

 

Before you spend $225 on a new computer, go to Advance Auto and price a remanufactured unit. I got a 1227747 for like $75 + trade in. I'm guessing that you checked and double checked the timing?

 

Yea, I checked the timing a couple times. I just called a junkyard and it's $75 there, I'm going to definitely get it there.

 

Niether.

Disconnect the ECM power for at least an hour. Remove and re-seat the connectors for the ECM. Take the HEI module in for testing (usually free). Install the module, then reconnect ECM power and see if the problem still exists.

Jumping the vehicle may have only created a surge that trashed the BLM tables of the ECM RAM. Dumping power for an hour should erase all the RAM and force the ECM to write new tables. It might be all that's necessary.