4.9 running lean

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Sep 17, 2014 | 09:33 AM

White Mountain Goat

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4.9 running lean

93 with 4.9. Was running great, no issues at all. Fueled up at a new service station, about half way through the tank it started losing power. Under acceleration it would bog down, and when climbing hills at highway speeds it lost all power. I pulled codes and got 171 and 174, so I checked for vacuum leaks and changed the fuel filter. It did fine for two days, then right back to being lean.

Long story short, I've put three fuel filters on it and ran five bottles of heet through it, I even ran about three gallons of gas out and it still does the same thing. When I fill the tank it quits for a while and runs great, and when I turn sharply to the left it will cut out and buck, but not when I turn right.

Since it stops when I fuel up, I'm thinking it must still be some bad gas in the tank. But water should settle to the bottom, not stay on top. Got me a little confused. I even replaced the O2, sensor. Any ideas?

Sep 17, 2014 | 09:46 AM

blue924.9

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do you always fill up right away or let it bog for awhile, fuel pump pickup could be broken and only sucking to half tank, or sucking air cuasing lean condition, have you check fuel pressure at the test port in the fuel rail?

Sep 17, 2014 | 10:07 AM

White Mountain Goat

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No, I run it till its near empty. I've given thought to the fuel pump possibly being a problem, but dismissed it as the entire pump assembly is less than three months old. I know it could still be bad though. I haven't checked pressure at the rail, and to be honest I don't know how. Do you need a special gauge or would a regular tire gauge suffice on the relief valve to get a general idea?

Sep 17, 2014 | 10:14 AM

blue924.9

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i will be honest i am not sure as i have never done it either, most people rent a guage from napa or another auto parts store.

another though i had was stuck or dirty injectors or possible an air intrusion in the fuel system

Sep 17, 2014 | 10:18 AM

White Mountain Goat

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I'd thought about the injectors too. But given that it runs fine for extended periods I don't think they are clogged.

Sep 17, 2014 | 11:40 AM

timbersteel

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Don't use a tire psi gauge to check. It wasn't meant for it and it'll create a wonderful fire hazard as its spews highly volatile fuel everywhere.

Sep 17, 2014 | 05:14 PM

Lead Head

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Autozone has a fuel pressure tester you can rent, but for whatever inane reason it comes with a bunch of other crap, so you need to shell out near $100 to rent it. You do get it all back though once you bring it back.

I'd suspect a broken fuel pump module, or maybe a loose filter sock.