Not so stupid car question

[VetteLT193]

I'd ask elsewhere, but this is where the brain power is....

2005 Lincoln Navigator, 5.4 6 speed auto.

Normal RPM's runs just fine, got 20 MPG on a beach trip this weekend... But, if you floor it, between 3000-ish and 4000-ish it gets sluggish... last 2 times check engine light has come on flashing after flooring, goes into limp home mode for about 15-30 seconds and then things are fine again.

Also, at really low RPM, like 40-45 MPH 1200-ish RPM if you try to accelerate I get a knocking... not the noise, but the shaking. If I manually kick it out of overdrive all is good.

I'm thinking I have a bad sensor and the spark advance is too advanced at certain times. At least that is what it feels like. Any ideas are greatly appreciated.

[Conquistador_del_mar]

If it were mine, I would first change out the fuel filter and have the computer scanned for the check engine light code along with checking the fuel pressure (any good shop can do this). I have also had good luck with cleaning the air sensor with Berryman's B-12 sparay and adding a couple cans of B-12 to the gas to help clean out the injectors, lines, and sensors. You might want to upgrade to a higher octane fuel if this solves the problems. My two cents, Bill

[VetteLT193]

Fuel filter changed 5k miles ago... although I didn't have the problem before I changed it so maybe something isn't right with it.

The way my week looks I may not get to this until Thursday so I might borrow your scan tool up in Kentucky :nilly:

[BUIZILLA]

did you get E85 instead of E10 crap? :frown:

they are both junk liquids, one's just junkier than the other.. :nilly:

[VetteLT193]

did you get E85 instead of E10 crap? :frown:

they are both junk liquids, one's just junkier than the other.. :nilly:

E10 and I buy from the same station. Although, they just switched not long ago from the real stuff so that's another change I have to think about. The 5.4, at least mine, hates E10. It's such a PITA to find real gas anymore though.

[BUIZILLA]

do NOT leave town without changing the fuel filter again...

and carry a spare

if the station just flipped over to E10, and their existing tanks aren't E10 friendly, you'll get a TON of residue in your filters or worse yet, clog the injectors..

a LOT of independent stations around here that aren't supplier owned are just closing up, and removing the old tanks and bulldozing everything, they just can't afford the tank upgrades that are E10 and E85 compatible

[VetteLT193]

do NOT leave town without changing the fuel filter again...

and carry a spare

if the station just flipped over to E10, and their existing tanks aren't E10 friendly, you'll get a TON of residue in your filters or worse yet, clog the injectors..

a LOT of independent stations around here that aren't supplier owned are just closing up, and removing the old tanks and bulldozing everything, they just can't afford the tank upgrades that are E10 and E85 compatible

The station is less than a year old if that means anything... I'll do the filter again just to rule that out. I'll be under there anyway for an oil change tonight.

The odd thing is it runs fine wide open after 4000 RPM, that's why I was leaning towards a spark advance issue.