The Excursion has had a knocking sound for almost a year now. It's random and only does it at stop lights waiting. When the light turns green and accelerate through the intersection, it goes away. If you put the transmission in Park or Neutral it also disappears. It really sounds like a fuel knock, but the transmission load has me stumped...and I would think a flex plate would get worse given how long it's been going on. I've also read about the belt tensioner...which I think is original...also producing a similar sound. I tried to get a video, but it's hard to by myself...

 

Take belt loose then try again to see if it does it. Will rule out your belt tensioner or not.

 

I'm leaning towards fuel aeration. It's to erratic to be belt drive, more like random injectors picking up a slug of air and pushing it through. At least that's my guess.

 

Had a chance to drive it after being down for some maintenance/upgrades. It started again so I removed the belt and started it up. It seemed to have went away with belt removed, then came back again when re-installed belt and cranked up again. I checked pullies and tensioner, and nothing seems overly loose...though the tensioner does move a little to one side instead of straight when applying pressure with a 1/2" breaker bar to get the belt off/on.

 

I'd bet tensioner judging by that info

 

Are all the grooves of all the pulleys clean? Even a small bit of gunk can cause noise. Other than that I agree the tensioner sounds suspect.

 

Today I switched tensioner and idle pulleys with my F350 and it's still there. I feel every other belt pulley and it's all tight except for the power steering which has a bit of in/out play...about the same on both trucks. I went to pull out of the driveway and it started up so I pulled right back in, removed the belt and it started again without the belt. I had our daughter put the truck in drive at idle while holding the brake to see if I could tell where it might be coming from. It sounds like it's coming from the front passenger side of the engine...like cylinder 1 or 2. I can put my hand on the air conditioning bracket and can feel the knock through it. It's just odd to me it only does it in gear...either forward or reverse...at idle, when you give it a little go pedal it stops.

 

Today I swapped back the idler and tension pulleys. The I pulled the fuel filter and it looked a little dirty, but not bad, so I went ahead and put a new one in...I think it was right at 15k miles on it. I also did the same for the small see through NAPA 3007 filter pre-pump. I'm still getting the knock but don't notice it when then engine is not up to operating temperature...like when you first get it started for the day and head out. Once it's up to operating temperature is when it starts. I've kind of ruled out a cracked flex plate given this has been going on for 2 years...it comes and goes...and is just enough to be annoying. I was just under the valve covers doing glow plugs etc. and didn't re-torque the the rocker arms, but I did feel them to see if they were loose and everything seemed okay. It's just puzzling to me this has gone on for so long, yet nothing comes loose or breaks...

 

Hook up Forscan and pull up the PERDEL'S PID's. It's not going to show what's wrong but it may show if something is actually going on and hopefully narrow down the where. Have you done a buzz test or any other self tests?

 

Yes on the tests, but I have time tomorrow and will get some more done as I'm wanting to figure this out...

 

So a little update. I hooked up Forscan and looked at ICP and IPR, which nothing is out of the ordinary. I decided to disconnect the ICP to see what happens. When I looked it was the original unit that came on these trucks from the factory with the 3/4" nut on the bottom. Disconnecting the ICP seemed to make the knock more faint after a short drive. Before hooking it back up I noticed some oil in there, so I grabbed another identical spare oem original unit and replaced it. I remember several years ago I replaced the EBP sensors with Zibbix units and also picked up the same brand ICP. I put the Zibbix unit in my F350 and the original functioning oem unit out of my truck in the Excursion. For some reason I thought both trucks got the new Zibbix ICP units. So anyway, the spare dry...I've checked it 2-3 times now since installing...oem ICP seems to have made a big difference in the knock as I can barely hear it, though it's still there. In looking back here I found what started all this was when the knock previously showed up and once I replaced the IPR it seemed to go away...though I couldn't find anything wrong with the oem IPR. I have another brand new IPR...off brand like what's in the truck...so I ohmed all 3, then made sure the 2 out of the truck rattled when shook. The oem IPR ohmed at 10.8, the new was at 11.0, and the one in the truck was at 10.6 plus or minus. So I noticed a little oil on the back side of the one which came off the truck...could have been from installation...so I cleaned it up and installed the new 11.0 winding on the valve still in the HPOP. This seemed to make the knock even fainter, especially when running the a/c. I just didn't have time to pull it and install one of the other valves. I plan on doing that within the next couple of days and see what happens.

I still also would like to check fuel pressure, though I would think if it was low it wouldn't run as good as it does when you put your foot in it. I did notice a little bit of a fuel leak around the line that comes off the FPR...it's very small such that it's just residue...but I can smell the fuel faintly. I've read about a screen getting dirty in the FPR, but I think that might be for OBS trucks...is that the case, or is there also a screen in the Superduty units? Both trucks still have the original FPR setup, though I do have rebuild kits for them.

In conclusion, I seem to be making some headway on this knock, and it appears to be fuel and/or oil related. I feared it might be flex plate and/or torque convertor related, but for as long as this has been going on it would have gotten worse like the F350 did when it developed a crack around the mounting bolts...

 

In a follow up I'm 95% sure I found and fixed the problem. I left the ICP unplugged after the truck started random hiccup issues and the last caused the truck to die, though it started right back up after coasting to a stop...see the thread here: https://www.ford-trucks.com/forums/1...ant-hicup.html The truck hasn't been getting the fuel mileage it used to about the time this knocking started a while ago...3-4 mpg less...which is why I did the maintenance items like leaky up-pipes, but the poor mpg still persisted. I plugged the ICP back in, started it up, and disconnected it again with no change in rpm. I now suspected the ICP to be bad though there was no oil in the plug and no codes for it. I ordered and installed a new Zibbix ICP and noticed a difference in the way the engine sounded at idle. I've driven it for several days with no issues and it just seems to run smoother. I filled the truck up yesterday to drive a little bit to see if the mpg comes back too.

 

Sounds a lot like the knock I'm getting with mine. Generally sounds great until engine warms up, then I have a knocking noise. Hopefully will get back on mine next week