Engine/Transmission (1998.5 - 2002) Stumbling/Hesitation

[Big P]

I'm posting this for my brother-in-law. He has the same truck as mine but without the comp. He reciently had a new vp44 installed because of the 216 code and other driveability issues. Seemed fine for a couple weeks but it now has stumbling condition under constant no load throttle, although he said it seems to run fine on cruise. He said it will clear up with a wack of the go pedal and seems to accelerate fine. I'm not sure if there are any codes now, but it kind of sounds like a bad APPS. What do you guys think?

 

[dpetre]

I would check the fuel pressure coming from lift pump. I took my to a Dealer in Fairbanks AK and the dealers said I had 9 psi at 2200. That was Friday on Saturday my truck had 1/4 tank of fuel would not go over 50 mph. I filled up performance went back up. Monday I took the fuel filter out and the lift pump would not fill the filter bowl up. My truck would stumble and do all kinds of weird things. I think it is all related to not enough fuel.

 

[Big P]

I don't think it's fuel pressure or fuel volume. He is running a FASS and pressures have been verified at 18 idle and won't drop more than a pound or two.

 

[KIseminger]

Are any additional codes coming up with the new lift pump?

 

[Big P]

No.