Trying to identify a sound

[Johnstra]

I know it's pretty near impossible to identify a sound over the internet, but I'd like to hear some opinions anyway.



What I hear is not a tick or a knock. It's more like one cylinder just has a little more thump to it than the others. It's definitely one cylinder and it follows engine RPM. There is also a bit of a pulse that goes with the sound. At idle, if I stand by the exhaust there's a definite pulse to the exhaust flow. Idle is not perfectly smooth, but it's not what I'd call a lope either.



So what do ya'll think?



-john

 

[MMeier]

Injector going south?

 

[steved]

Injector going south?

If it is, mine has been doing it for over 30k miles!!!!



Mine has the "lope" or "bump" tone in the exhaust (almost a bump-bump-bump tone)... I noticed it a while ago... but it may have been there a lot longer (30k was when I installed a slightly quieter muffler)...



steved

 

[Mhannink]

my bet is there is a valve way out of spec. run the valves, set them tight and see how it runs. i think it will be a lot better

 

[Johnstra]

Hey Steve, maybe it's our Gulfcoast



I've been reading the "Ticks and Knocks" thread and I don't think my sound is the same. Mine just doesn't sound like a spark knock. With the radio off and and the windows up I would almost swear it sounds like an exhaust leak. It's not like a metallic knock or tick.



Anyhow, my mileage is good (20 mpg unloaded), it starts right up, it doesn't smoke, power is great... so whatever it is it's not hurting fuel economy or power.



-john



I ran the valves a couple of months ago and they were all right on spec.

 

[steved]

I ran the valves a couple of months ago and they were all right on spec.

As did I... and I was very anal about the adjustments...



Mine sounds like a very slight lopy cam in a gasser... and depending on where you are in relation to the truck, it may or may not be there...



I hear it primarily in the exhaust, at the tailpipe... and it is a definite bump-bump-bump tone underlying the main "rrrrr" of the exhaust. I don't know what it is, but I know mine has done it for over 30k... I was concerned that it was a failing injector, but the thing runs like a champ, nets me almost 20 mpg, and there was no fuel in the recent UOA I completed...



I don't know what it is... and I have no possible explanation. However, I know that I have also heard 2nd gen trucks making the same tone as well...



Although I don't think it could be a valve, maybe??



steved

 

[Mhannink]

well at school we where told that anything but smooth exhaust flow meant a miss wich could be a number of things on a diesel with these new electronicaly fired injectors the computer might not being firing it long enough a valve could be out of adjustment or the injector its self is not quiet right.



food for thought in our engines class we had a 3406b with what sounded like a slight miss at low and medium rpm levels but at wot it went away turned out to be a nut that was in the intake valve so the valve wouldnt close all the way but at higher rpm it would bounce around more and let the valve close and no more miss.

 

[Johnstra]

I adjusted my valve lash again carefully and it did clean up the sound of the engine quite a bit. I still have what I guess I would call a knock, though.



When the engine is cold, the engine is very smooth at idle and while driving. As the engine gets to operating temp, the knock becomes noticeable. It's pretty mild but it can definitely be heard. While driving, it's most noticeable under load between 1500-1800 RPM. It's not a tick and not a ping. It's more of a tapping sound in rhythm with engin RPM. At idle, listening to it outside the truck it just sounds like the idle has a beat to it.



Does this sound like an injector or something else?



Thanks,

-john

 

[DLane]

Injector getting carboned up. Have the same problem with my 05. Valve adustment "helps" in the early stages but most definately a injector. Unplug the injectors from the harness on set at a time (ie 1+2 = same plug ect) and you will be able to narrow down which one(s) are going bad.