96 454 Falls Flat When Warm

[GaryRoe]

1996 3500 single wheel pick up, automatic 454.

 

Truck runs great cold, but when it warms up, will idle only. Only code showed was MAS AIR, so I replaced it, and the fuel filter. Unhooked the battery. Now, no codes but does the same thing. Gonna test fuel pressure hot and cold tonight...what else?

Thanks in advance.

[yukon25008.1]

I had an 00 siverado 454... same vortec motor.

Sounds like when it gets warm somethings pulling timing and/or fuel out of it..My 01 350 van was doing very funny intermitent things, and it ends up being the computer or "pcm"

Very hard to diagnos..we had low fuel pressure at 1st and waisted 300 bucks on a new delphi fuel pump. Have someone with a decent scanner like snap-on modis, check it and start flollowing wires.