Slight Knock at idle only.. fuel??

[roperteacher]

I noticed my 04. 5 now has a slight knock when idling ONLY. No loss of power, runs smooth as glass otherwise. Getting 22+ MPG unloaded hwy. Put in power service and that really helped. I am wondering if I just got a weird tank of fuel?? I just had the truck serviced and dealer replaced fuel filter etc. Sounds like an injector, but not all the symptoms. This could be the normal knock some talk about?? I have 37,000 on the clock. It is not an every day thing either. Seems to do it worse once warmed up rather than cold. . which is odd. Thanks!

 

[RustyJC]

Don't know about the HPCR and its cetane sensitivity, but let me cite a case that happened to me.



We were at the iRV2.com National Rally in Nashville, TN not far from Opryland just off the Briley Parkway and getting ready to head home. I fueled up at a station not far from the campground, hitched up the 5th wheel and headed west for Texas. The combustion rattle and knock was so bad that my wife and I couldn't even carry on a conversation without yelling at each other, let alone hear the CD player.



This went on all the way to West Memphis, Arkansas when I refueled at the Flying J. Immediately upon hitting the Interstate, the engine quieted right down and was fine for the rest of the trip.



So, at least in our case, fuel CAN make a huge difference. Having said that, I recognize that the 2nd generation 24 valve HO is probably the noisiest Cummins ever put into a Dodge - especially with a timing box!



For what it's worth.....



Rusty

 

[roperteacher]

Thanks! I topped off last night to just get some other fuel in there. ALready better from what I can tell, so I am not going to worry about it. Especially since I am not "Making oil" , smoking, loss of power, etc. Certainly at HWY sppeds it is quiet as a mouse.

 

[JCleary]

I filled at a Chevron once (well, I usually fuel at Chevron, but this was in another county) and almost immediately my truck idled and sounded like a 2nd Gen. It was super loud at partial throttle and idle.



I was so afraid I had injector or injection pump problems (I always use Stanadyne to prevent this).



I filled again 500 miles later and all was back to normal.



I guess our motors are sensitive to contaminated or bad fuel?

 

[roperteacher]

Yes, this was at an Indian reservation here in Southern california. I won't name names. But their fuel was 20 cents cheaper than other stations so I thought I would give them a try... I got what I paid for!!