I took my car in for emissions and it passed however as I was driving home it started backfiring. I checked the cap/rotor/wires/plugs (all are new anyway) and they all are fine. Strangely though, when I go to check teh timing and I unplug the brown EST wire, it doesn't make any difference in idle. The EST and distributor both have 125k on them, so does the coil. Any ideas?

Thanks,
Mike89GTA

 

i wouldnt believe the book on this one. i chased that same problem around in my corvette forever. it wound up being a bad computer, throwing code 42 about 90% of the time when you would start it. occasionally it would run without the code 42, but once it threw the code, it started running like crap, backfiring, and whatnot. i finally tested the computer from my iroc in the corvette, bam, problem solved.

btw, code 42 is supposed to be a fault in the ignition module, but i replaced that, traced the wiring completely back to the ecm, and still came up empty handed until i tried the computer as a last resort.