So I have a 08 5.4 with 115,000km on it few notes to start that might help with the issue to come,

no rear cats, no codes, no custom tune (dont know if i need one for deleted cats, if dont get code) fuel filter done about 20,000km ago and FPCM just done a week ago. Edge readings: spark advance BTDC* 9-24 idling in drive and 3-18 in park in both they rapidly change constantly, never stays steady its all over the place back and forth between the min and max numbers i shared. fuel rail pressure of programer reads 38-39 at idle and 30-43 with key on.. whatever line pressure desired means on an edge tuner it shows 48. The truck idles at 630-666 and about every 5-10 seconds it changes tones from the higher end and then drops to the lower of those number and constant at the exact same timing every time.. dunno if thats normal or not, doesnt seem to be an issue.

so now the problem..

so i think the fuel pump and sending unit are gone but maybe something to do with ignition as well?

-I have a constant whine noise but only under very light acceleration, not at idle.. only about the first half inch down on the gas pedal. (bad fuel pump noise?)

-Randomly sometimes when at a red light in drive the idle turns into like a lope tune and drops right down but truck never dies but its luggin away, then once you hit the gas and get going it goes away almost instantly.
sometimes spark advance goes down to 3* while driving too. (fuel or spark problem?)

-Fuel gauge works most of the time but sometimes it goes below empty when i have a full tank, sometimes takes about 30 mins to go from empty to full when i fuel up, or will only go to 3/4 when i just put a full tank in..(sending unit problem, with the float im thinking is the only option for this?)

-sometime very rarely the truck will kinda lug or surge under very light accel when driving from a stop..usually when theres a little incline or something and my foot is barely in it.

i think that is everything with this issue i am having..
im sure if i throw new plugs, new coils and a new fuel pump/sending unit at the truck it will all be fixed.. but not sure if i need it all or what is wrong exactly..
thanks for any help!

 

I would try the simple stuff first...clean the throttle body and MAF

 

That truck has before and after O2 sensors right?

 

Ive cleaned the throttle body but i dont think ive done the maf yet, last time i looked at it it looked perfectly clean. and yah all the O2 sensors are in it.. The back ones are in test pipes and restricted from some flow so that the codes dont go off.

 

bump, any more suggestions or ideas?

 

not sure about 08 5.4 but my 01 had a dirty IAC. i took it off and cleaned with brake cleaner and replaced everything was fine. idle would go down around 400-500 at a light, once i got going it was fine. kinda a bitch to get to being behind the intake next to the firewall. sounds to me like your gas gauge is bad, common problem, craigslist is loaded with people advertising fixes. whine you hear could coming from your FEAD, tsb on noise when temp drops to 40 or below. my 08 mustang gt does this or could be a vaccum leak.

 

Honestly sounds like a vaccum leak to me , I would look for a cracked line or a line that has come off its connector

 

Thank guys will look in to it all hopefully today, checked for vacuum leaks and non i could find.. Tried the way with ether aswell, the humm noise i have comes from mid to rear truck not engine bay by the way

 

check your exhaust I have had a clogged cat. that had a similar sound

 

Well two cats are gone, the rear ones.. So the front ones would be in the engine bay basically.. Unless the sound would be coming out the tail pipe.. But it is only under very light accel and no other condition.. Was yours like that?


Thanks