Ford 4600 engine vibration. Help!

[sawtooth]

So my 4600 runs smooth except from 1600-1800 rpms. Anything above 1800 is fine also. Any idea what could cause a vibration in this 200 rpm range? Do these engines normally run this way. I know it's a 3 cylinder but the vibration is a little uncomfortable so I end up running below 1600 or above 1800 to bypass it. Any ideas?

 

[sawtooth]

Anyone?

 

[sawtooth]

Update. Well it ended up being dirty injectors. I ran heavy dose of Opti-Lube for 2 tanks and now smooth as can be. Still going to use that stuff but at lighter normal dose rate. Food for thought incase anyone else has same type issues.

 

[trmechapt]

Also older tractors don't get enough lube through the fuel any more so put an ounce of eng. oil or two stroke oil to the gallon of diesel.
Gary

 

[sawtooth]

Also older tractors don't get enough lube through the fuel any more so put an ounce of eng. oil or two stroke oil to the gallon of diesel. Gary

Thanks but that's me main advantage of Opti-lube. It had highest lubricity rating while cleaning injectors, increasing Cetane, providing a anti gelling agent, and fuel stabilizer. Your right though needing lubrication for the old mechanical injectors.