Anyone here a C4 guy?

[101lifts2]

Originally Posted by Avatard

Why would the code scanner not pick that up?

BTW, it seems to get worse when it gets hot. I let it cool a bit, and it restarts feeling much better.

It misfires so fucking bad that the cats start to smoke.

I would run the engine with the MAF sensor unplugged (has to be unplugged when ignition is OFF). Let the computer run off of speed density instead of air mass. If the misfire is never apparent, then replace the MAF sensor (they are notorously junk). If it still misfires, then look into the optical spark system, though they usually only fail if they get wet. My 93 Firebird with a 5.7 used to act up (misfire) on occasion come to find out it was the opti spark getting wet.

In earlier years (pre OBD2) the oxygen sensors had a large amount of authority in which would actually make the engine misfire. After OBD2, the calibrations were such that at the 21% +/- fuel correction would set the code, but not cause the engine to miss. You can also unplug the O2 sensors and see if it still misfires.