went to start up my 4 cyl 1999 grand am today. Trac off light is on, won't shut off. black out of tailpipe at start up for a minute, and jumping everytime it shifts. it has a sealed tranny, so I have NO IDEA where to start. also service engine light came on. it was on a few weeks ago, but place said it was O2 sensor. but it's back on. this car never ran this rough. I did put injector cleaning in at last fill up, and tank is down to 1/8, but thats all.

Thanks!!

 

Did you replace the O2 sensor? Get the code numbers and report back here.

 

You didn't state engine size, but I'm betting a 2.3 or 2.4..........The "Quad 4" engine........The 4 bolts on top of the engine will release the ignition components as a whole.............Invert the top and you will see a rather large coil tower containing both ignition coils. The connector runs to the ign module........Check your plugs and replace as necessary..........and I'll bet if you replace the coil tower, your problems will be over.......Clear the codes and drive vehicle, as a missfire, overtime, will set a whole bunch of codes .........one of which will be O2.....