2003 Ford F150 4.2L Engine acceleration hesistat while driving

I have this car, which i am working on, Car came towed because original engine was dead, and had to replace engine and tranny complete. I had the engine replaced by another mechanic.


Car got started, but when you put it under load, car wont be able to climb hill, new fuel pump was replace, yet still, MAF sensor was also replace yet still car wont be able to open with full acceleration,

Launch Scan tool was put on the car and code came out as

P0171 and P0174, all this codes are pointing to lean in the system, i have smoke test the intake system but could not find leak but yet whenever car is place under load and hard acceleration, you get this lean fault codes. please i need advise what to do, this car has it fuel regulator valve mounted on the fuel rail pipe...

i did current check on the fuel line and it shows exact current rate of the alternator charges, i also place fuel gauge tester and i got 35 psi at engine off , key on, then when the engine is started it between 38 40, when rev, you see the gauge going a above 40, but wont get to 50 exactly,

when you hit the accelerator pedal down to the floor, you will that the engine is not opening, and you will hear sound like the something that has to do with the air flow, you will hear cow sound noise, like choking sound of air or something , i dont know how to put that sound here..


i need advice.

if live data stream is needed, i can use my launch scan tool to record and post here, but will like to know which main items to select for this record, thanks in advance...

sorry for my english

No problem! I'd suggest attempting a WOT run through first and second gears (if it'll get there at all). Watch these PIDs:

-Engine speed
-Loop status
-MAF voltage (or g/s if you're in Global)
-Load %
-Both upstream O2's
-Short and long term trims on both banks

On a good truck, the MAF should get to 4V or darn close at peak engine speed. Load should go above 80%. Both upstream O2's should go over 800mV and stay there while your foot is on the foor.

When not doing the WOT run, observe your trims. High at idle, or high when cruising? Don't worry about what they do when in Open Loop, just Closed.



There's also a handy flow chart that explains the process:

Do these engines have multiple coils or just a single coil/distributor?
It sounds very much like the Ford I worked on with a cracked coil - it just couldn't handle anything beyond idle.

i agree with tyler about looking at those pids. maybe try unplugging the maf as a quick and dirty test and see if it drives better. only other thing i can think of is restricted injectors or fuel quality. i dont kno what the fuel pressure is supposed to be off the top of my head.

Here are links to some video I made-:

www.mediafire.com/file/6qcu8nj0qk1kncc/5...1DBC2BA7B4D.MOV/file



www.mediafire.com/file/drw71l78fu6gtk3/0...2347D9D8357.MOV/file


www.mediafire.com/file/ib9dgjxg3i6ir98/6...5E6CB633F33.MOV/file

Single coil, with plug wires moving from the coil to the each individual spark plugs. The coil is 6 in 1 coil

Desmond6004 wrote: Do these engines have multiple coils or just a single coil/distributor?
It sounds very much like the Ford I worked on with a cracked coil - it just couldn't handle anything beyond idle.

Single coil, 6 in 1 coil, with plug wires going to it

cheryl hartkorn wrote: i agree with tyler about looking at those pids. maybe try unplugging the maf as a quick and dirty test and see if it drives better. only other thing i can think of is restricted injectors or fuel quality. i dont kno what the fuel pressure is supposed to be off the top of my head.

The car stall or dies when you remove the airflow sensor wire from it.

Thanks for the videos! The trims getting much worse off idle definitely suggests a fuel delivery problem.

Any chance you could do another capture with those same PIDs (plus the upstream O2's) at wide open throttle? That'll help clarify which direction to go with our diagnosis.

Tyler wrote: Thanks for the videos! The trims getting much worse off idle definitely suggests a fuel delivery problem.

Any chance you could do another capture with those same PIDs (plus the upstream O2's) at wide open throttle? That'll help clarify which direction to go with our diagnosis.

i will update you with that video by tomorrow, more over i have removed the convertor core from the exhaust system today because i was thinking may it may have choke, that is why car cant move, or open on fully acceleration but this removal did not work the system out, it still craw when you hit accelerator down, it cant climb hill talk-less to mention mountain... 5 fuel pumps has been changed, yet still and even new fuel pump complete is in the tank now, but still the problem still persist, when i place manual fuel gauge on the line, at the Schroeder and turn key on, pressure rise to 35, and when engine start and at idle, pressure increase alittle above the 35 psi, and while accelerate it also increase a little, but not exceeding 50 psi, between 45-48psi..

i have also check the current over time on the fuel pump wire near to the pump, the current report constant alternator current, so means no drop at fuel pump side.

one thing to add, car has quick start,

Thanks for the additional info.

I keep trying to put your lean trims together with the 'cow noise' you mentioned in the first post. :lol: Not making fun of you - I know exactly what you're talking about!

You've ruled out exhaust. A restricted intake won't cause lean trims. Fuel pressure is good (I checked your readings against Mitchell)... Was this a used engine? Was the harmonic balancer transferred from the original engine, or did it come with the new one? Wondering about a timing issue. Shifted keyway, slipped tone wheel, like that.

Maybe have a close look at the tone wheel for the CKP when you get back to the truck.

Tyler wrote: Thanks for the additional info.

I keep trying to put your lean trims together with the 'cow noise' you mentioned in the first post. :lol: Not making fun of you - I know exactly what you're talking about!

You've ruled out exhaust. A restricted intake won't cause lean trims. Fuel pressure is good (I checked your readings against Mitchell)... Was this a used engine? Was the harmonic balancer transferred from the original engine, or did it come with the new one? Wondering about a timing issue. Shifted keyway, slipped tone wheel, like that.

Maybe have a close look at the tone wheel for the CKP when you get back to the truck.

The engine is a used 1, from the junk yard. When the engine came, the harmonic balance on it got broken, so I had to change it with my old engine balancer. I used the ckp sensor of the used engine obtained from
junk yard seller which came
With the engine, I only changed the harmonic balancer, has the tooth gears on it.

One thin I forgot to mention, before I did not remove the catalytic converter core, was when I have being getting the LEAN fault codes even though there is no leak, after several smoke test, but now that I took out the converter core from the exhaust chamber, those two codes never appear again and to add more one of the core was turning to powder in it casing when it was opened. So it was also a good idea to have taken it out but yet the car won’t climb hill still, and also it has quick start, infact one touch key turn will fire the engine with gladness.

I have not meet this kind of strange issue before but am determine to solve this issue, I pray for more ideas from professionals in this forum. God bless you all.

Well, Tyler thanks for getting the point am trying to make with the cow noise, it’s funny though but am grateful you got me understood, hope others also does.

I will check the harmonic again and update you,