Hi all, Ok so I have a 01 f150 with 4.6 for about a week now when accelerating lightly when it gets to about 2000 rpm its kinda flat it will like hang there for a second, not really like its missing, but its like a flat spot when I punch it its not as bad still feels like its lacking power but it revs right up. The only things I have done recently was change the diff fluid (lucas 75 140) I cleaned and re oiled my air filter and put new plugs about three months ago I did also clean my maf sensor a couple weeks ago with maf cleaner. Thank you for your replies.

oh and I am getting no codes with my scanner+ my fuel pump seams a little bit louder than usual

 

Begin by checking fuel pressure.
Next look for a flat spot in resistance or intermittant/open on the TPS somewhere in the lower end of it's travel.
Make this measurement with an Ohm meter from the black lead to the center output lead.
Or measure the voltage accross the same leads with the key on, engine off, while opening the throttle.
The voltage will go from about 1 volt to about 4.5 to 5 volts. It must be smooth with no intermittant.
Good luck.

 

Hi and thanks, I checked the fuel pressure with key on eng off its at about 19 with engine running its about thirty if i rev it up a little it spikes up to about 33 35 then drops back down to 30 and the needle is steady it also holds pressure. I will check the tps now.

 

Ok I checked the tps I think I did it right, with the black lead on the center wire and the red lead on the top wire I am getting this reading At idle its reading 4.00 and wide open throttle it goes down to .33 v Maybe I did it wrong

 

The voltage check was backwards. You measured the wide open value down to low but should still have picked up any roughness.
Ideally the fuel pressure should be a bit higher in the 35 range at idle but should not cause a flat spot.
Seeing the pressure change with throttle opening changes indicates the regulator is able to control the pressure by the change in engine vacuum through the control hose.
At this point I have nothing to offer for a flat spot condition except maybe the EGR is opening when it should not, due to a sticky vacuum control solenoid regulator leaking vacuum to the EGR lifting it off it's seat.
Remove the vac reg and clean it with throttle body cleaner and clean the filter under the round cap.
It's located right behind the power steering fluid bottle.

 

Now by roughness, do you mean when I pull full throttle it should be quick like from 1 - 4 instantly Because when I did it (snapped the throttle open) it did kinda stopped for a milla second at like 1.30 then up to four. I hope that make sense lol. I am changing the oil now and looking over things and I noticed the rubber intake hose going to the throttl body, the hose clamp was loose as hell it seemed to have a decent seal, but would that be just enough to create a slight vacuum leak?

I also have a decent actron scanner that gives live data and graphs.......just not sure what Im looking at when it comes to the graphs and parameters.

 

The voltage reading needs to be smooth and unbroken.
This sensor's signal is used for a number of functions.
Among them is transmission shifting point vs RPM, EGR control, deceleration indicator,
the rate at which it increases it's output is detected and used for extra fuel upon rapid acceleration, unlocking the torque converter when throttle is lifted rapidly in cruise and more, so it's operation is very important.
.
On hoses, sometimes it can be a source if the engine vacuum opens up a leak at idle when the vacuum is normally the highest or on decellertion when it is even higher.
Or even pull a fault open upon a call for heavey acceleration so it depends.
Keep at it.
Good luck.

 

I cleaned the regulator and the foam filter rapping up and gonna test drive it here in a minute. Thanks again for the help!!!

 

well no luck it is actually idling kinda rough now Im at a loss???

 

When was the last time you changed the fuel filter?

 

been about 15 months I actually just went up and got a new one. gonna put it in now

 

How old are the plugs? My idle isnt exactly smooth either but I know its time for a plug change also so maybe that? Like Bluegrass suggested maybe the EGR is hanging or not ****ioning properly. Would an IAC issue cause this? I have no such "hang" but a flat spot in the rpm band from about 2k-3kish. Is it an abrupt pause?

 

LOL I spelled functioning wrong and it edited me...

 

Hi, plugs are pretty new 2 months and gap is good,I also cleaned the IAC valve a while back cuz I was having really bad idle and stalling issues, I also think that I got a code when that happened, the throttle inst like a pause its smooth from 1k up to 2k then when it shifts into 2 gear from like 2-3k its almost its to high of a gear to soon? now this only happens when the throttle is applied light, when I hammer down its not that noticeable hard to explain hear is a silly question I changed the diff fluid and I used lucas 80/140 that stuff is thick, is it possible that it is creating a little more drag? I changed the fuel filter....boy it was dirty,the idle smoothed out a little bit,I gotta tell you ALWAYS BLEED PRESSURE OFF BEFORE CHANGING FUEL FILTER I thought I had all the pressure out and when I disconnected it it sprayed out something fierce and where did it spray? RIGHT ON MY JUNK, ha ha its funny now but wasn't a hour ago as I run past my wife from the garage butt *** naked and fly into the shower tears coming from my eyes!!!! any ways lol thank you guys for the in put

 

What brand are the plugs?