Runs great then Runs bad. I'm at a loss.

[Robdgx35]

I have a 1989 GMC Sierra 5.7 l 350 V8. I put a new fuel pump in, fuel filter, did a throttle body repair kit, new regulator, new fuel injectors, new fuel injector wiring pigtails, new map sensor, distributor cap and rotor, and spark plugs, new spark plug wires, new PCV valve, I also checked the fuel pressure it was at 11 PSI I believe it is supposed to be between 9 and 13. I banged on  catalytic converter to get the dirt out if any. I change a few other parts out as well. It runs really well at times and at times it will not start or rough idle or as soon as I try to get going it stops. I have completely ran out of options. Oh and I also checked the fuses and I put a new relay on as well for the fuel. Like I said sometimes it runs really well but then other times it runs like total crap. Please if anybody out there has had these issues I would really love to get some answers. Thank you

[Jglew82]

The ignition control module inside the distributor is a common cause of this. 

[Z45]

If you used any ignition parts besides genuine GM/AC Delco parts that may be the problem. So many parts are sourced from the far east and are terrible quality (cheap components) no matter what the brand name on the box is.  I have a friend in the repair business who will not use anything but oem ignition parts. Way to may failures with the cheap parts that its bad for business.

Edited June 15, 2021 by elcamino

[el profe]

did you find your problem?  i am going through the same darn thing with my 91 c1500....very frustrating