Chevy 3500 8.1l running lean when engine bay is hot

[Taylor21-05]

Hey guys, new member here.

I've got a 2006 Chevy 3500 with the 8.1 motor and the Allison trans.

 

It's the work truck and tows a trailer always.

We do hydroseeding, and when the truck is towing a heavy load, or sitting idling for too long and the engine bay gets hot, the truck won't give full throttle.

It's always different, as far as I can tell, based on temp.

If I idle the truck with the hood open it helps.

I cleaned the mass air flow sensor. And it doesn't seem to be fuel starvation.

 

It's throwing a code for left and right bank lean mixture.

 

 

Any ideas?

[Raptordude]

How hot is it getting on the temp gauge?

 

 

Sent from my iPhone using Tapatalk

[davester]

can you hook up a pressure gauge on the fuel rail to verify that the fuel pressure remains constant? And are all the bolts still present on both exhaust manifolds?

[Formulabruce]

I would first Flush the whole cooling system when engine is NOT hot, really flush that radiator well. Old Dexcool can beak down and clog stuff up.

[txab]

Check fan clutch for proper operation

[dewfpo]

Also clean the IAT (Idle Air Temp) sensor. They can get gummed up and give false air temp readings to the ECM.

 

DEWFPO

[Taylor21-05]

Temp gauges read normal.

I should find a fuel press gauge to try.

 

The truck got a new radiator last year, so I would hope the coolant system is clean... And yes the fan works. You can hear it engage climbing a real steep hill slowly (when it won't allow full throttle)

[MCAT069]

My 8.1 loved it when I changed to a 185 thermostat; it gets hot here in Texas. When you are flushing the system, you might consider a different thermostat.

[Formulabruce]

gas is probably boiling, this alcohol fuel has been doing that and causing posts on many boards about it. Insulate the fuel line where you can near anything hot, get a 160 T stat for it, it will still run in closed loop.

[dewfpo]

Check your fuel pressure. If the fuel is boiling in the line that could indicate a low fuel pressure issue.

 

DEWFPO