Van runs rough after warm restart

[MR.Pizza]

Hey guys, I could really use some help trying to figure out this problem I'm having. My mechanic seems to be stumped and we will be doing a fuel pressure test tonight.

Vehicle is a 2000 GMC Savana 3500 5.7L with 230,000 miles. The van is my daily work van and otherwise runs fine.

The issue is only when the van has been driven and is left to sit warm for even a few minutes it will start fine but will stumble and almost stall out with no power some back firing for about a minute and will then suddenly clear and drive fine. This has been an ongoing issue that sometimes will go away for a while and then return. Fuel mileage has never been great but the van otherwise runs excellent.

Recent repairs:
Intake Manifold Gasket Replaced Due to Coolant Leak
New MAF
New Coolant Temp Sensor
New PCV
Ac Delco Plugs & Wires
Accel Cap & Rotor
Cleaned IAC
Cleaned MAP
Cleaned EGR Tested Fine
Fuel Filter Less than a year old
Regular Oil and Filter Changes

Last week I replaced the cap and rotor, put some Lucas injector cleaner in the tank and it seemed to go away however it seems to be back. Last week the weather was quite mild so I'm not sure if it's temp related.

Thanks

 

[caddydude]

Savana van loss of power

Mr Pizza, I had the same problem with my 1999 Savana and was pulling my hair out trying to fix the problem. Turns out it was a bad O2 sensor(before the Catalytic Convertor). Un-plug it and test drive it. I couldn't believe it.I thought they usually cause a rich issue not a lean one. A mechanic friend pointed me in the right direction and he's getting a free lunch at least. Jim from Michigan