98 vortec 7.4 issues

[Daniel k]

hey guys having a issue with my truck and need some help. It’s a 98 vortec 7.4, Problem is timing is all over the place going from 0-38 degrees. It’s missfiring and backfiring out the tail pipe and you can smell gas and see black smoke coming out the tail pipe. And truck won’t rev over 1300rpm. And barely idles(it’s jumping between 360-1000 rpm) I have done the following. Compression test,(all at 135-140psi) smoked the engine(no vacuum leaks detected) new distributor, new wires, new coil, new icm, new plugs, new o2 sensors, cleaned maf and throttle body, new cps. Triple checked the distributor was in the right way. Checked timing chain play, new temp sensor. No cel lights on. What to check next?

 

[Schurkey]

Connect a scan tool, look at the data stream.

Cam sensor/crank sensor/distributor all in synch?
Coolant temp sensor reading correct temperature?
Short- and long-term Fuel trim look OK?
Knock sensor not going crazy?
MAP sensor , TPS showing normal readings?