Hi all- I have a 98 Chevy C2500 pickup (5.7L Vortec 350) that I am having a real frustrating time with. A few weeks ago, I noticed that very occasionally, after the vehicle was warm, I would see a sudden full RPM dip to 0 while driving down the highway, but then the vehicle would return to normal operation. It would happen quickly and would not be any sort of aggressive sputtering.
Then it got to the point where I would have been driving my 10 minute commute on the highway, and then when I took an exit and started driving at 20 mph or so, the truck would completely die, or stall, not sure which one to call it. I would have dash lights, but I would have to quickly shift to N and turn the key off and on and it will fire right back up.
It doesn’t sputter then stall, it just dies and then starts right back up. A few times though it was a bit hard to start it back up. I’ve read that could indicate a failing fuel pump. I can hear the pump loud and clear though so I know it is working at least most of the time.
It seems to idle very low, and my oil pressure also gets down to around 10 psi at idle when the engine is really warm.
It rarely will die at idle, it seems to mostly happen when driving at around 20 mph.
I will stress that it really doesn’t stall DURING acceleration, but instead AFTER I have accelerated and then slowed back down.
I have changed spark plugs and wires, cleaned throttle body and MAF, and cleaned the IAC valve. I also replaced the fuel filter.
I have read stalling problems with these engines could be EGR related, TPS, IAC, ICM, etc.
The truck is in a shop now, and they called me today and said they drove it for a long time, probably 30 miles or so on the highway, and they could not get it to stall. They say it ran perfect. This is just an annoying coincidence- the other night it ran good for me and didnt stall, but It has stalled on me almost every day multiple times in the last week. I told them I will come in and drive it with someone and hopefully get it to stall so they can see.
Anyways, does anyone have an idea what could be causing such an incredibly intermittent stalling issue like this? It doesn’t seem to be fuel, because it doesn’t sputter before or after it stalls. Should I just start replacing easy parts like the ICM and TPS myself? Could it still be my fuel pump? What could be getting hot and working differently than when cold? Could it just be my battery is bad? It is a bit old. Could that be distributor cap and rotor? I didn’t replace those yet (just plugs and wires).
Could it be the fuel pump relay gets hot and somehow stops making a connection?
Any help would be greatly appreciated! I don’t have the money right now to chase this problem endlessly with an auto shop…