Retrodog

Hi all,

I have searched around for other knocking engine posts but have only seen one even remotely similar to mine. And that one did not have an answer yet.

My symptoms are that the engine knocks and sounds like an air hammer is rattling away under the hood when I am in passing gear or even when i am in park and revving above 2000rpm. (it also sounds similar to the noise a diesel engine makes when its running)

I have no power loss or hesitation and i am not burning anything out the back end. i have tried a tank or 2 of higher grade gas to see if it is poor quality gas but that did not fix it. i change my oil regularly and put synthetic oil in at every visit. there is no CEL active and i do not notice any loss in my gas mileage. If it weren't for the sound i would have no other hints that the engine is unhappy. It does appear to be getting louder and occurring for longer stretches when I am in passing gear. the knocking goes in time to the rev of the engine.

Any ideas on what to check first?

realtree4x4

i dont know what your problem is but ive heard ur not supposed to put synthetic oil in older motors.

Have good one bud

porrietae

i have the same problem. some say it's caused by the vacuum seal in any 4x4. mine is a 4x4. but i still have not got a response by anyone who has had this problem fixed. i don't want to fork out too much $$$ at this time before i know what the exact problem is.

Retrodog

I recently tried higher grade name brand gas (Shell) instead of the grocery store gas i had been going with and once that got working i noticed about half the knocking going away. I then thought maybe i need to clean the injectors out so i had one of those services done where they get under the hood and and hook up to the fuel line and run the engine pulling in some kind of detergent. once that was done the engine went right back to full volume knocking just like it was a day ago.

my next step will be maybe to check the O2 sensors. the engine seems to not knock when i am at a stable speed. it only knocks when i am accelerating very aggressively or if i let off the gas slightly just after acceleration. it seems that the knocking occurs when the engine has to rely on sensors only. i dont know enough about the innerworkings of the computer but ive been told that there are mapped out fuel mixture ratios stored in the computer and that it knows how to set everything when there is a stable RPM but when things are in coast thats when the computer relies on the sensors the most. if one of the sensors is fouled or broken that could be the source of my problems.

FYI mine is not a 4x4 and i have been using synthetic oil for the 9 years i have had it. Its been running reliably since the day i got it so im not quite convinced that i shouldn't be running synthetic oil in it yet.

colton

mine has a diesel-sounding noise like that, i wonder if it is a vacuum line for 4x4? ive had my entire 4x4 assembly completely apart, and it was all in perfect condition but it wont engage unless i do it manually from underneath so i figured that was probably a vacuum line related problem. sure would be nice if that fixed the noise too. where is the seal that usually goes bad?

mine also has another noise similar to the one youre talking about, but i know it comes from the exhaust manifold. it isnt extremely loud or bad sounding, but its noticeable. a stud broke on it and when i got it fixed, i think the manifold had already warped creating a tiny exhaust leak. it doesnt sound like an exhaust leak though, more of what youre talking about. but i know thats what it comes from on my truck

Retrodog

Took the truck to a shop and had them look at it and their opinion was that it is a rod knocking and that the engine needs rebuilding or replacing. now the question is how much hassle do i want to go through. I could sell the truck and get a newer one or look for a lower mileage engine and do a swap-out.

on a side note. i had the oil changed a few days before Christmas and they told me at the shop today that i was 3.5 qt low. i dont have drips and i dont see anything smoking out the back end. that part has me most baffled.

transmaster

With all of the F150's available on the used market I would get another truck. Your truck is getting to the age where it just is not worth the hassle. Unless this truck has some special significance to you personally dump it and get an another one. If you are looking for a good place to pick up a nice F150 come to Wyoming there are late model F150 on at every car dealer in Cheyenne, usually three or four of them and not just in Cheyenne, every car dealer in the region is filled with really nice Fords. One big consideration Wyoming does not use salt on our roads to clear snow. I was just looking today and you would have your choice of standard cab, Supercab, Crewcab, FX4 and 2X4, most any engine. Want and F250 a bunch of those as well. There is even a good selection of F350's. Years? 2000 and up. I see you are in Dallas, Texas I would image used F150's are no strangers on your local car dealers lots either.

Maybe somebody here with a rusted out 1999 is looking for a new truck for his engine