94rangersplash

2001 f150 4.6 v8. It will run fine the first 15 miles of driving or if it is below 80 outside it will do fine. But if it idles for a few min after driving for 15 miles or so it'll run like crap. If you push the gas more than a 16th of the way down it boggs down it does it in park and in drive. The rpms will go to around 3000 then it'll just bogg and drop back down but will idle fine. If you slowly get it too 2500 rpms and hold it there its missing really bad shaking the truck then push it about 1/4 of the way down it boggs back down again. Sometimes when im holding it at 2500 then push it all the way down it'll back fire through the intake. Then i can turn it off and sit for a few seconds it starts and runs fine for a few more miles. It seemed like clogged exhaust but it only has 70000 miles and i did two different vacuum gauge tests on it and it passed both of em. Through all this the check engine light has never came on but i hooked a code reader up anyway and it said i have no codes. The part of this that gets me is i can turn it off then back on and will go fine. Someone give me some ideas cause its been over 90 degrees everyday for about a month now. Replaced fuel filter a week ago and put E3 plugs and 8 new COP about 5000 miles ago air filter is good and just changed oil too and took egr off and inspected and cleaned all that was good

punkorpunket

maybe check the fuel filter and fuel injectors im not sure i never had that problem but maybe they are clogged and thats part of it. i dont know but its a start i guess

westtnfx4

Clean your MAF sensor....next fuel pressure/filter.....

94rangersplash

Cleaned MAF and it didnt help anything. Then i hooked a fuel pressure gauge up and idle it is at 30 psi and with the vacuum line off the regulator it goes to 40. When i slowly give it gas it stays around 30 all the way till it hits the rev limit. Then i can hit the throttle about half way down quick and hold it there and the rpms will raise to about 3000 then bog down and the fuel pressure will drop down to 20 then slowlly go down to about 5 then i let off the gas and it goes up to 30 and idle fine. I also tried it with the line off the regulator and it did the same thing prolly a little worse even. So i then hooked the gauge up to my 94 ranger i have and it has 30psi idle but when i gas on it fast the pressure goes up to 40psi and holds till i let off then back down to 30. I also hooked a vacuum gauge up while it was bogging and at idle it is at 20 but when i gas it fast and it goes up to 3000rpms and boggs the vacuum goes to 0. but if i slowly increase the throttle it stays at 20 on the vacuum gauge all the way to the rev limit.

spyder98

wow thats exactly what is happening with mine. Ill be doing plugs, boots, fuel filter and air filter this weekend see if it helps

Mechhell

I just had similar symptoms, It ended up being the filter sock on the fuel pump, Its was full of mud and sand, After purging the fuel tank and a new fuel pump I'm hitting RPM's i've never seen before.

spyder98

how hard was it for you to drop the tank? any special tools needed? where u able to buy just the sock? or is a new pump recommended?

94rangersplash

Yea after i seen the fuel pressure readings i figured that replacing the pump and sock filter was next for me. I am not going to drop the tank to do it though im pulling the bed back. I did it on a 98 f150 and all i needed was a t50 bit (i think that was the size anyway) for the 6 bed bolts and the fuel line tool which is only about 6 buck at the auto parts store. The only other thing you need is 3 friends to help pick the bed up. I've done it both ways putting fuel pumps in, dropping the tank and pulling the bed back, and doing the bed is easier to me. If you drop the tank the fuel lines dont have much slack and you have to reach up with little room to fight the quick connect fuel fitting and it was a pain in the butt to me.