2002 F150 , 4.6 , cats removed , 02s in blind bosses.
truck gives very high trim # at 2500 rpm + or on full throtle . Perfect trim #s at idle or at driving speeds.
No vac leaks, did smoke test , no misfires, only codes that show are P0171,P0174 . Cleaned MAF sensor , new air filter.

If I step full throtle it shifts down, revs up but has no power to increase speed, let up on gas and it runs decent and trim comes down to +3,-3 ranges, both short and long trim.
02 sensors read .1 to .7v , both short and long term trims will go up to + 50, under full throtle and drop to normal almost instantly when throtle is let up. . Where do I look to get some power for hills or passing., and not be showing lean codes on both banks ?

Truck has 450,000 km, starts great down to -30 , doesnt burn oil, has high oil pressure ,.

Any help is apreciated.

Thanks
Pete

 

You cannot use full throttle "trims" for evaluation as those are open loop values.

Pull your freeze frame data for those TDCs. If the stored data indicates the faults occur at high RPMs or heavy loads, then you have either a weak fuel delivery process or a MAF sensor that's incorrectly reporting the intake air mass.

I'd suspect a restricted fuel system or a weak fuel pump. Try measuring fuel pressure when the symptom occurs and see if the pressure sags when demand spikes.

 

Thanks so much . I am still thinking old school, carbs etc, so this is new to me , and lots to learn about all these numbers.
I will try a new fuel filter and clean the MAF again first to see if that helps .My fuel pressure at idle is 55psi, on the scan tool, so hopefully a filter is the issue causing grief.
Thanks again
Pete

 

55 psi is way above spec. It should be 28 to 40, verify with a mechanical pressure gauge on the fuel rail. When you remove the vacuum line from the regulator on the rail, it should rise 5 to 10 psi.

 

We're interested in the fuel pressure "at failure". Unless the thing fails at idle, it's not a relevant data point.

BTW, the "book" says "30-45 psi" at idle speed. 55 psi at KOEO is not a concern. However, if it's reading "high", then the actual pressure is going to be far lower and the engine won't run right off-idle or under load as it will be then starved for fuel.

 

Truck has 450, 000 km and OP wants to know how to make it faster......

 

Pete, you can't measure fuel pressure with a Scan tool on your year.
There is no sensor for the PCM to use.
It has to be measured with a physical gauge attached to the test port on the fuel rail..
The fuel regulator has vacuum control attached to the regulator for the purpose of LOWERING the pressure at idle.
The motor does not need that much fuel at idle.
If there is high pressure, the regulator is faulty or the return line is pinched closed..
Clear this up for us.
Good luck.

 

It's got drivability issues. He's getting "lean" codes and it's gutless under load. It's not a matter of trying to "go faster".

 

Thanks , its to bad every forum has smart *** trols , but as long as we are smart enough to ignore them we can get great information and help with things we dont know or understand .

Yesterday I drove it again and for unknown reason to me it pulled much better , the scan tool was not on so no numbers, but drivability on hills was much better . This has me thinking the computer may be just slowly adjusting , so when I replace the fuel filter today i will also reset the computer by disconecting battery, and toutching the leads together , as was sugested by another source as something to try .

My old fuel pressure guage is dated , and not compatable here, thats a new tool I guess I need to upgrads for todays vehicles .

Thanks To all that are helping this dinosaur get things working better.

 

Most parts stores loan out fuel pressure gauges.

 

Well the plot thickens . On my way to the city to buy a fuel pressure test guage it seemed to be running good , acelerating and shifitin good ( , for a truck with 450,000 ) but still good.
The hardest thing to do is fix what isn't broke .
so for now I will leave it as is, untill it acts up again. If it does , this thread gave me some good direction . I will get a guage when I am in the city , for when I do need one.

 

Maybe you picked up a load of bad gas? Throw some Techron in the gas and if available, fill it with gas with no ethanol.

 

I did run some injector cleaner thru the last tank , that may have helped . As for bad gas I doubt it , I fill at busy stations , and we are only an hour away from the refineries . All gas arou d here has ethhanol , and it has never been a problem , in any of my vehicles . It helps prevent gas lines icing up too .
with luck it keeps running good .