Tractor Surging

Massey Ferguson 5465 is surging quite noticeably. I originally noticed it while under very light load at approximately 1400 RPMs. It was steady enough that you could probably have checked it with a stop watch and it would have always been the same. It may run smooth for 2 seconds, then (opposite of surging I guess) it would drop RPMs for just a split second. It was very steady and predictable, so it's not fuel filters. The tractor was running fine at idle or full power. Pulls good with no noticeable reduction in power. Tractor is 2008 model. Injector lines show no signs of leaks. Maybe a bad injector or what are your thoughts?



Thanks in advance!!

Tractor Surging