97 5.7 intermittant misfire

[alhutto]

My 97 C1500 5.7 will at times stumble,bog, and missfire and not go above about 3500 rpm.No codes wiil set and if I stop ,shut down the engine, and imediately restart it the problem goes away and the engine runs perfectly. This all happens when the engine is fully warmed up and in closed loop mode. It almost seems to randomly go in to "limp mode" but simply cycle the engine off and restart it and everything is fine.The engine is a relatively new crate engine with fresh ignition components. I cleaned all the PCM connector pins as well as the pins an connectors on the TPS,map,maf, and knock sensors.It seems to me that something "resets" when I cycle the engine off and on it will run fine for a few days which makes me think either the PCM or a major sensor has a problem but, again ,no codes are set. I guess the knock sensor could have a defect that shows up intermittantly causing the PCM to retard the timing or some other sensor doing the same thing.This thing has really got this old man puzzled. HELP!

[W/T_Deluxe]

hmmm I've seen fuel pumps cause an issue like this. I had one in a 96 tahoe that would act similar to this and actually had good fuel pressure, but the pump was a bit noisy so I threw a pump at it and it fixed it.

[Dirtautoguy]

I had a similar problem except my truck would stumble and sometimes just flat out die but if I cycled the key a couple times and started it it was fine come to find out it was the fuel pump relay, so I replaced it which fixed it for a while and started doin it again but it was because the new relay didn't fit tight and would work itself loose. I just bent the prongs a little so it was tight and I haven't had any problems with it since.