odd problem, need help please

[drawlin]

hi, I have a 91 300zx n/a 2+2 auto. it is runing rough, often miss fireing. have tried different things I could think of; checking the spark plugs, listening to injectors, reseting cpu, even cleaning connectors on the ptu(this seems to help some, since it runs smoother afterwards, but returns to the normal rough idle after a little bit). I have a datalog of a ~20 min drive, but i'm not sure what to be looking for. The 02 graph looks a bit funny, but not sure.

Any ideas? should I take it to a dealership and have them run a diogostic on it?

[LIBRILZ]

I'm having the sam problem too. Soemtimes It will be at 1200 RPms then 600 or then I shift it and it sound like it wants to die but it dosen't and goes to idling at about 1000RPMS.

[drawlin]

hmm, also seems that the timing is geting retarded at odd time, probably because of the missfire. now to figure out what's causing the miss.

[tri5lvr]

As soon as I get time, I'm going to check the O2 sensor. If the plugs are durty, then so is the sensor. This will tell the computer it is running rich and it will try to lean it out. Also going to try the throttle position sensor. It might have a dead spot. Will let you all know what happens.