I have a 2004 F-150 Lariat 4WD, 150K on new engine and 308K on truck. Engine idles a bit rough. Someone on the forum helped me about 6 weeks ago. I have replaced both knock sensors, new plugs and coils. Seems about 1800-2000 rpms something starts happening. My mileage is averaging 14.7, which seems OK to me, but you can tell something is just not right. Almost like its gasping for air and it does not have the acceleration or power it should. It ides rough.

I put the knock sensors in first and ran it for a couple of days. Guy at auto parts said that if I did not do the plugs and coils at same time I could of ruined the new knock sensors.

Every once in a while, I get a "hard brake" but does not happen all the time. Tansmission seems fine to me.

The codes say knock sensor and running lean.

Also, when I put the knock sensors in, I tore up the fuel line to the rail. I patched it with fuel hose, and it does not leak, BUT I had to install a brass connector between the old fuel line and the new fuel line, which was a tad smaller than the hose, and maybe its restricting fuel flow.

I am wondering if I have a vacuum leak somewhere else and do not know where to look. Also, wondering if it could be as simple as the fuel filter, but do not know where it is either.

Any help or direction to go would be appreciated!

 

the main fuel filter should be just inside of the frame under the driverside door, I replace mine every other oil change s a new filter is only like 10 bucks and super easy to replace with the little line removal tool, and i am currently running into the same issue and actually had a vacuum hose come off of the back of my intake man. it is almost impossible to get to, im waiting on parts now but I had to remove the fuel rail to get back there and still havent got to it, cant really see it as it is behind the motor almost against the firewall. maybe worth looking into, oh and BTW I got the codes P0174 and P0171, both banks being lean

 

James: I need to tell you to get the vacuum line on, under the manifold is a bear. I could not do it. And it is probably what my problem is. I could not attach the hose to the plastic mainifold, to both tube ends and get everything to go back. So what I did is when to autoparts store and bought the same size tubing and slipped over the attachment points. I made the hose about 1.5 foot long. I wish now I have also put clamps on the hose, because it is a real pain to get to the hose. I asked a mechanic on this site how to do it, and he told me its almost impossible ( but possible) however, sometimes he takes off all the stuff under the engine and goes in that way. Yikes! The FORD hose is about 6 - 8 inches long and is pre-bent. I guess that is what you have ordered. If you figure out a neat trick to get the FORD hose on please let me know...thanks, David in Houston

 

SUCCESS! I most definately agree with everything you are saying, I managed to get my stock hose back on, I had no idea what I was really getting into so firsd I removed the air system, then disconnected the fuel rail from injectors, didnt take it all the way off just moved it foward so I could get my hand behind the intake, then I fished up the hose that was blown off and did some inspecting and with some feeling around and a small mirror I found the fitting and wow! it was almost impossible to even see much less get a hand on. so what I did was put a zip tie on the end of the hose just snug enough so it wouldnt come off and got my left hand back and on the fitting and with my right hand passed the line down to my hand already on the fitting and used the tag end of the zip tie to pull it down, got a hold on it and wiggled it on and synched the zip tie down! put most everything back together and fired it up and still ran like crap WTH!! well I discovered soon after that it wont run right if the air filter is not in! got it in and it is running perfect!

 

I hope other people see this, seems it is a common problem that takes a lot to figure out, I spent 400 bucks, a week and went though 3 mechanics just to find out it was simply a hose that came off...

 

Cool...I will try the zip tie method!