Whats the problem

[snipersm7]

I have a 1996 k1500 with new 383 vortec engine. Trucks starts up, runs but under throttle throws p0300 code. After it warms up 5 to 8 minutes, it starts to sputter and die. It does this consistantly after it warms up and usually around 1500 + RPM. New fuel pump that has key on 60-66 psi. Runs 56-57psi idle and will raise sightly when I give throttle. After the truck dies, it will bleed off from 57psi of fuel pressure to about 45-50psi within a minute? Fuel Psi regulator? The previous owner has put on the upgraded MPFI unit. New spark plugs, new wires, new coil, pickup coil, new distributor, new EGR, new MAF, MAP and new intake gaskets. Any suggestions. I have tried another coil, pickup and still same problem, same P0300 code thrown...

 

[Jesse_Wenting]

I have a 1996 k1500 with new 383 vortec engine. Trucks starts up, runs but under throttle throws p0300 code. After it warms up 5 to 8 minutes, it starts to sputter and die. It does this consistently after it warms up and usually around 1500 + RPM. New fuel pump that has key on 60-66 psi. Runs 56-57psi idle and will raise sightly when I give throttle. After the truck dies, it will bleed off from 57psi of fuel pressure to about 45-50psi within a minute? Fuel Psi regulator? The previous owner has put on the upgraded MPFI unit. New spark plugs, new wires, new coil, pickup coil, new distributor, new EGR, new MAF, MAP and new intake gaskets. Any suggestions. I have tried another coil, pickup and still same problem, same P0300 code thrown...

P0300 indicates that two or more cylinders are experiencing misfires. I'd check that the new MPFI unit was installed correctly, almost sounds like 2 or more of the lines were misplaced. Not sure why it would run and then die but it's a start

 

[Erik the Awful]

Runs good when cold, but dies after warmup, and previous owner had the intake apart? Check for vacuum leaks.

 

[snipersm7]

I have new gaskets on intake both upper, lower and the throttle body

 

[1997]

are you using a code reader or scanner?
Some code readers don't give you the whole picture since P0300 is a generic code where for example P0301 would be for a cyl1 missfire if your code reader can read it.

You can use a vacuum guage (old school and cheap) to check for vacuum leaks, easy to check.

Good scanner, MPFI would be a good place to investigate, maybe something not seated or installed correctly.

Keep us posted, good luck.

 

[snipersm7]

What should the fuel pressure range be. I am getting within 60-66, key on no start. About 56-57 psi idle and running. The fuel prssure does bleed down within a couple of minutes from 56psi to about 45psi and then 40psi after about 5 min.

 

[1998_K1500_Sub]

Head gasket leak between two cylinders? Problem arises after engine's iron heats-up?

Just a *wild* guess.

 

[SUBURBAN5]

I have the vortec 383 in my burb. Had a misfire pop up as well. I ended up removing spark plug 1 and found the gap was way off to the other 7. Now that being said I borrowed a coworkers autel scanner and found that I still have a misfire on the front portion of the pistons but they go away when driving. Also the misfire is not bad enough to throw a code. I've been suspecting it's the mpfi system since that's the only thing that I didnt change when I did the swap out. Also I would check for vacuum leaks as well. I've been meaning to check mine for ***** and giggles but havent done it yet. Last like the others have said make sure your not leaking fluid to any piston. In my case I've been maintaining my coolant level and when I checked my plugs they looked normal. But if yours is the ht383e I would highly recommend checking the gap and using a scanner to see exactly what's the motor reading. Plus with the scanner you can check your timing in the distributor goodluck , keep us posted

 

[snipersm7]

Update. I removed the upper intake manifold, found some leakage from fuel injectors in the back. I replaced the MPFI unit, with a new standard MPFI. The missing codes went away, it starts up and runs good for about 5 to 8 minutes. When it gets to operating temperature it would sputter and die just like before. Now my PCM is throwing a P0337 and a P0339 codes. I replaced the Crank position sensor already. It does have some wire exposed on the yellow signal wire near the crank position sensor. I did measure the air gap and it is over .100 gap..... I am getting 12v to the pink wire in the connector.

 

[snipersm7]

Replaced the MPFI, trouble codes PO337 and PO339 went away. Now I have the CMP code showing and so I have to find a scanner or app to set the CMP retard offset...........