My Fuel Is Leaning Out On Wot

[justin95]

I checked the pressure if its around the right pressure but the guage moves around when it should be still. My fuel pump doesnt make any noise and runs great, but on WOT it is getting lean. Anyone know? Im getting my truck tuned by Justin and this is how we figured out it was lean. Heres what he said:

 

"He has one of my scan cables, working on his tune. Extremely lean at heavy throttle (in PE mode). After one look at the log, he's not allowed to go above 2/3 throttle til this gets figured out. No apparent intake leaks, although that is still the likely culprit (in speed density, it's nice and rich in PE mode). Had him check fuel pressure and it is erratic. 56-59psi with vac line to the FPR disconnected, should be a rock solid 58.

 

He's replaced the MAF, that fixed part of the problem (fuel trims diving to -15 at closed throttle), but it's still lean with any amount of throttle.

 

Does anybody know of the 8.1Ls are known for intake gasket leaks like the earlier small block gen-IIIs?

 

Justin"

[michigansilver03]

Due to pressure not steady I'd look at the regulator

[justin95]

Yea, It wasnt steady, but the vacuum line on the ragulator was sucking. For some reason he ruled that out, but i dont really know why. Were thinking its a vacuum leak some where. He said "Your MAF is showing less air than it should. About 20% less. 20% of the air coming into the engine is coming in from some source other than the MAF. "

[justin95]

Also, the truck runs alot better with the MAF disconnected.

[Draenor]

Still sounds like the MAF. What is the MAP? If it is within pramaters, I would rule out a intake gasket leak. What is the fuel pressure at WOT?

[justin95]

I replaced the MAF, but the problem is still there.