I just installed a new Opti spark in my 95 Trans Am. When I go to start the car it turns over then immediately backfires. I'm not sure if it backfires out of the intake or the exhaust, but it sounds like its from the exhaust.

Before, when the car had bad opti still on it, and I tried to turn it over it made no backfire; it just kept turning over. So somethings different with the two optis (Im hoping that the old one's bad and the new one's good)

Did I install it wrong? Wires misplaced? Timing off?

I did notice on one of the connectors that goes into the coil, one of the plugs was missing one of two prongs..... I don't know if that could have something to do with it or not.

Also, the car is throwing a service engine soon code and it was not on before I installed the opti.

The history on the car was I took it to a shop to replace the headgaskets at 103,000 miles. I was there when the shop started the car up and it ran like ****; smoking and idleling rough until it finally died 3 months later. I am thinking that when they took the water pump off, they dumped antifreeze all over the opti. The car ran better after I installed new O2 sensors but it still skipped up high (~4500rpm) until it died. When I drove at a low speed in a high gear it would back fire like crazy. Right before it died, it started backfireing and ideling funny and then it made this weird metalic dragging sound.

So now I have a new opti, wires, plugs and a coil in and it won't start. I cant scan the code it's throwing though.

Any ideas? May be it wasn't the opti after all?

 

you probably installed the opti wrong, it will cause it to backfire like that...

 

Check your wire placement and find out what the trouble code is.