My 2002 F250 7.3 with a little over 270,000 miles on it, has been making a knocking noise lately, mostly at idle. I think it sounds more like it is coming from the drivers side, but am not for sure. It is definitely coming from somewhere in the engine, but I'm not sure if is an injector or the engine itself. Not sure if it matters, but the mods it has are a K&N intake, 4in exhaust, and TS chip.

It is not a constant knock, it comes and goes. I only hear it after driving the truck. It seems to do it when I first drive it, and then once I go far enough to fully warm it up, it goes away and I don't hear it again. Even then, its still not constant, but still easy enough to hear. I heard it again today, but only after driving it enough to warm it up, and then shutting it off. Once I got back in and started it up, I heard the knock again, after not having heard it before. It has done it like that before, so it seems to start knocking after having been driven and shut off once, and then started back up again. The truck seems to run and drive fine to me though, except for the knock.

So I only hear it after driving the truck, and its not a constant knock, I don't always here it, it comes and goes. It almost seems to start, or get worse if I get on it a little bit, not sure if that means anything or not. I'm hoping its just and injector or fuel pressure issue, but I'm not for sure. Hopefully I gave you guys enough info to help me figure out what is wrong. If you guys have any idea of what could be causing or making this knocking noise, or some tests I could do to try and figure out what it is, that would be greatly appreciated it. Thanks guys!

Here's video of my truck at idle when I heard the knock. Its happened many times other than this. Not the best video, but you can still hear the knock. You can't hear it as well in the second clip though. It might be easier to hear both better if you have headphones though.



Also not sure if this is a related issue or not, but lately the truck has been getting some pretty poor fuel mileage. I hand calculated it the best I could, since I'm not sure exactly how much I put in or how much I used, but I've got a pretty good idea. So hand calculated it was getting about 8 or 9 mpg, at best 10 if I was a little off on my calculation. I know fuel mileage will go down in the winter, but that seems too low to me. That was with winter fuel, warm up times, a lot of 4x4 driving, and lately I have just been leaving the hubs locked because I use 4x4 almost everyday. With all that factored in I know it will knock it down quite a bit, but like I said it just seems too low to me, but maybe not. Also it has been I think, a little too smoky on cold starts, but I also could be off on that. What do you guys think?

Thanks for any help!

 

Well I am not sure I can help , just give you a place to look, I was also having a knock issue and thought a injector or harness was going bad. One day driving to work my truck just died. towed it home and with help from this forum found out my fuel pump on the frame rail was bad. I replaced it a couple weeks ago and my truck has never run better, starts better , have not heard the knock and fuel mileage seems better. I also have 204000 miles on a 2000 with dp tuner, 4 inch mrpb exhaust and 6637 intake. hope this help something to check

 

I hear a loose injector. There is a distinctive metal "tick" to the sound that I can catch at 1:30 and on. With all those miles on original sticks, it could be a bad injector... but checking the torque is free.

 

Rich, that tick you point out sounds almost exactly like my sound, but mine is clearly louder. I'm going under the hood today - it'll be a balmy but sunny 32° this afternoon - but before I start I'll try and get some video / sound to post if it'll help anyone else out.

RedDevil, get some hose and try and listen to the valve covers, if it's only one ticking from one side, that'll save you a lot of work in the cold. That is one frostly looking truck.

 

IMPORTANT SYMPTOM OF LOOSE INJECTORS:

You will likely get "bucking" at moderate throttle, like accelerating gently up a grade. The bucking will disappear if you power up a bit more.

I am now to the point where I can tell which injector is loose before I pop the VC. From the limited sound of the camera microphone, it sure sounded like #8.

 

I've had a metallic tick like that since day one, even remained after I installed new inj o-rings....always assumed it was the AE #8 at play.

 

I can't completely rule that out, but air in fuel (the bane of #8) sounds more "cackly" and not "tinky" to me.

 

Well, I dove under the VC's today, and found #2 injector lower bolt not at the proper torque. It wasn't loose, even with a 1/4" ratchet on it it was gonna take a little effort to turn it. I also had some rocker arm hold down bolts, #3 & #6 most noticeable, that were less than 20ft-lbf, so I went ahead and checked all of those as well.

I pulled the #2 lower bolt, cleaned it and used Loctite with primer. Here's a link to the driver's side before fixing anything. The truck was cold for this, about 32° out, not plugged in.

 

did that help anything because I think I'm in the same boat as you are I hear the same sound every now and again

 

1/4-turn on the injector isn't a thing... but you didn't mention if you checked it with an in/lb wrench. It's hard to tell with a camera mic, but #8 sounded the noisiest from here. Does it have a knock down low by the oil pan below #8? My #7 has been doing that off and on for many miles. Make sure pushrods are good.

 

A long time ago I swapped my #8 AE for a AD injector. Did the intank and pre-pump mod. I raised the fuel pressure to 70 psi using a spring in the fuel pressure regulator. All this lowered the #8 knock by maybe 40%. Now it's very intermittent, sometimes it purrs like a kitten other times it get a bad knock thats almost a bap-bap-bap sound. It runs great and has good power so I just leave it alone for now.
Bill

 

My number 7 used to do that (until very recently). I have a 9th injector and I swapped out the offending stick. So far, so good.

 

I have an in-lbf torque wrench, craftsman, nothing special. The 1/4" referred to the size of the ratchet I used to see if the bolts were loose. I used that to see if I was able to loosen the bolt, and how much effort it would take, but I didn't actually turn the bolts. Then I used the torque to see whether the bolts were at 120 in-lbf or not. #2 needed almost a half turn before the wrench clicked. Then I removed the bolt, cleaned it and the hole, loctite, and torqued it, and the rest, to your higher 130 in-lbf.

And after all that, my truck has a slight tic, but that has been there for quite awhile.
And for this question, all of my injectors are AB's.

 

So... I'm reading this may have been more an exercise of being reassured nothing obvious is going on in there, and not an actual fix.

This could be a situation where my not being there to hear it and relying on a camera microphone skews my judgment and screws your day. I've made a note of that. I hope you feel reassured that nothing bad was going on under the cover and it's just a matter of injector or cam wear... it would minimize some of my embarrassment.

 

Oh no, there was clearly something extra ticking away in there on the driver's side. The regular light tick is on the passenger side. Going under the passenger side was a "hey, why not" moment, which found me an under torqued rocker bolt.

And, one more thing, can anyone tell me where the valve cover bolt, the one under the oil dipstick tube bracket, went when I dropped it? And, since you can't, where I might buy another?