Archived Engine Knocking Under Light Load!!!

[RobertP]

About three weeks ago I had and injector body crack while driving. Pulled off to the side of the road, after noticing a bad fuel smell. Found the oil level way over full and the under side of the truck soaked in fuel and oil, from the breather. Pulled the injectors sent them out. Replaced the cracked injector body and got some new nozzles put on. Reinstalled all of the injectors changed the oil. (Drained out about 7 gallons of oil and fuel mixture) started the truck up idled perfect nice and smooth no smoke at idle at all. Drove up and down the street noticed a what seems to be a timing induced knock. Starts as soon as there is a load on the engine and is completely gone by 2000 rpm. Programmed the ecm back to stock the noise lessened but was still there. Once again I sent my injectors out to have them tested all tests come back golden. (Again I have to thank industrial injection for putting up with me through all of this) I got my injectors back again today and installed them. Knock still there, and gets worse wheni put the program back in the truck. Checked all sensors for proper connections all good. Drove the truck home runs great still has a ton of power runs and idles great still. Just have this annoying knock from let’s say 1300-2000 rpm then it’s gone. im at my wits end with this thing. Oh yeah one more thing I put a new stock cp3 on thinking maybe that could be the cause. Any and all info would be appreciated. Thanks Robert. Feel free to ask any questions im at my wits end with this knock.



sorry for the long post!





new info. after changing programs to an older program the knock has lessened. but is not gone. it is just less pronounced. please advise!!!!

 

[RobertP]

well today i put it on the DRBIII ran the injector cut out tests and cylinder performance tests. all tested good. cylider performance came back perfect. funny thing after i drove the truck while running the injector cut out tests. the knock is gone. not there at all. its got me more confused than ever. but happy that the knock is gone.

 

[Missouri Mule]

It's great when problems solve themselves!

 

[cojhl2]

Raw fuel?

I wonder if there was residual liquid fuel bouncing around in the cylinder??



It's always scary when probs seem to go away and there is no explanation.

 

[RobertP]

on the way into work again this morning the knock was present. it was very slight i really had to listen for it. i could not hear it over the radio at a very normal level. so whatever this noise is it has gotten a lot better since the first time i heard it. but knowing that there is a knock somewhere in my engine is driving me nuts.

 

[cojhl2]

Are you sure this latest knock is not just imagination perpetrated by sensitivity to a previously unexplained issue?



Darn unexplained noises anyway. I have one that I also can't figure out. Drives me nuts, goes away when I turn slightly to the right.

 

[DKupec]

Fuel is very bad for bearings. If you had 3+ gallons of fuel in your crankcase, the knock you are hearing may be due to a bearing issue. The fuel thins the oil to the point that it will just wipe off the bearing on not provide a lubrication bearier. When this happens the bearings get eaten away at by the crank, rods, etc. I would get it diagnosed by a professional before you have a major problem. I wish you the best of luck with this and I really hope that your problem is not anything major.

 

[PRout]

How about trying an oil analysis to look for unusual wear metals.

If it comes out normal you can smile again.

 

[RobertP]

during lunch i ran an oil pressure test. oil psi at idle-55psi cruiseing in second and third is about 75-80psi. my shop forman was out on the lot and said it sounded like a rod knock. then i took him for a ride and it would not make a noise. if it were a rod knock it would be consistant. am at still at a loss on this one.


just in case this became a question i have been running amsoil with a bypass since 19,000 miles. i have 59,000 on it now. in that period of time the oil and filter have been changed 4 times. ive always been one for over kill. then just recently i changed the oil three times since i have fill the crankcase with fuel. but that was with just regular dino oil, until yesterday i put new fresh amsoil and filters on.