99 Tahoe rough running, backfiring, etc READ!!

[ZR800]

So initially thought it was the tranny. Stomp on the gas and it would not increase speed. But, do the same in Park or Neutral and same problem. Put the pedal to the floor, and the RPMS do not increase. Back off a little, and the RPMS shoot right up. Was going to start by replacing the fuel filter, but was told by a mechanic who happened to walk into the shop I was using that it was the spark breaking down. So replaced the plugs and wires instead. No change really, got a little better, but still doing it. (that was 2 weeks ago) So today replaced cap and rotor. Still doing the same. So went back to my original analysis and replaced the fuel filter, and bam- Running great, so I thought. Cleaned up, pulled the truck out of the shop, noticing it was a little rough, but had no time left. Locked the shop and jumped in the car to head home. I wish I hadn't locked the shop (it was left unlocked for me by the owner). Truck running like crap. Missing, etc. Now home in the cold garage, checked my wire order. Everything good. Popped the cap off, and reinstalled for the hell of it. No change. Found the #5 wire was loose at the plug. Pulled the plug, cleaned it, reinstalled. Running real bad now! Backfiring, spitting, barely driveable. Missing like crazy. Oh yeah, through all this, the check engine light has been on and off for a week or so. Its on now, and flashing sometimes. Going to have the code checked on Monday, but really need the truck driveable tomorrow. I put the rotor back in the same way the other came off. Thought plugging #5 wire back on would have solved all the problems, but worse now. Had the air cleaner "Vortec" portion on and off a number of times. Disconnected the batter for possible reset.



Anyone have any suggestions I can check before Monday?????

[GMMerlin]

The code you will find is a P0300 engine misfire.
The misfires most likely have caused damage to the catalytic converters.
I would check the exhaust backpressure to verify this.
Next is determining what is causing your misfire..secondary ignition or a fuel injection problem.

[ZR800]

So the truck is running fine now. Pulled the cats, hollowed them out. Put the old cap and rotor on, and bam- Running great now. Must be something wrong with the new cap and rotor I got.