Dud1f3r
Newbie
Hi, this is my first post, but I've been reading the forums since about April, when I bought this truck.
Some backstory, just to get you into the mindset of why I did all this to the truck. The truck is a 1997 K1500 with the 5.7L engine. I bought it off a friend's dad, who parked it for 6 years. Got a good deal on it, I figured it'd be a pretty easy truck to work on, and a good first domestic. Well, after getting it running (the dizzy was mistimed, I just pulled it out, retimed it, and put it back in, along with a new cap and rotor), my first goal was to clean out and replace the fuel system as good as I could. I replaced all the gas in the tank (for obvious reasons), replaced the fuel pump with a new Delphi unit, replaced the fuel filter with a NAPA brand filter, and replaced the spider injection unit with a "TRQ" brand (The 1AAuto brand) MPFI conversion, all of which are working great.
The issue now is it misfires only when warmed up, only under moderate/heavy load. First thing in the morning, go fire it up, and it runs great. Drive around for a bit, maybe 5-8 miles, and it's warmed up. Once it's warmed up, you can't do anything but just barely touch the gas pedal, or the truck will sputter and misfire, and it'll get worse and worse until it starts to misfire at idle.
I've replaced:
Fuel pump
Fuel filter
Spider injection unit (with MPFI conversion)
Intake plenum gasket set
Plug wires (But had to go back to the old wires as the new ones were making it miss constantly)
Dizzy cap
Dizzy rotor
Coolant temp sensor in the thermostat housing
When reading live data, the truck is getting up to temp fine, and all of the sensors are reading what you'd expect them to read. I've checked for vacuum leaks and found none. I've double checked my ignition timing, and without a proper GM tool or anything, it's fine. Only code is a P0300.
Can anyone point me in the right direction in what to look for? Despite what it looks like, I'm not too fond of just throwing parts at issues.
Some backstory, just to get you into the mindset of why I did all this to the truck. The truck is a 1997 K1500 with the 5.7L engine. I bought it off a friend's dad, who parked it for 6 years. Got a good deal on it, I figured it'd be a pretty easy truck to work on, and a good first domestic. Well, after getting it running (the dizzy was mistimed, I just pulled it out, retimed it, and put it back in, along with a new cap and rotor), my first goal was to clean out and replace the fuel system as good as I could. I replaced all the gas in the tank (for obvious reasons), replaced the fuel pump with a new Delphi unit, replaced the fuel filter with a NAPA brand filter, and replaced the spider injection unit with a "TRQ" brand (The 1AAuto brand) MPFI conversion, all of which are working great.
The issue now is it misfires only when warmed up, only under moderate/heavy load. First thing in the morning, go fire it up, and it runs great. Drive around for a bit, maybe 5-8 miles, and it's warmed up. Once it's warmed up, you can't do anything but just barely touch the gas pedal, or the truck will sputter and misfire, and it'll get worse and worse until it starts to misfire at idle.
I've replaced:
Fuel pump
Fuel filter
Spider injection unit (with MPFI conversion)
Intake plenum gasket set
Plug wires (But had to go back to the old wires as the new ones were making it miss constantly)
Dizzy cap
Dizzy rotor
Coolant temp sensor in the thermostat housing
When reading live data, the truck is getting up to temp fine, and all of the sensors are reading what you'd expect them to read. I've checked for vacuum leaks and found none. I've double checked my ignition timing, and without a proper GM tool or anything, it's fine. Only code is a P0300.
Can anyone point me in the right direction in what to look for? Despite what it looks like, I'm not too fond of just throwing parts at issues.