Had this issue intermittently last year and its back this year. 2003 DT225. Cruising along at 3000-perfectly smooth. Hit exactly 3500 and it sounds like (1) or more cyls drop out. I loose 200 or 300 rpm.If I pull back on the throttle a hair the rpm's flutter and the engine sounds good/bad like someone is throwing a switch to the plugs. If I drop it back below 3000 it all sounds perfect but it dies at exactly 3500 every time. No warnings on the computer smart gauge. New gas and the raycor is clean
my mechanic said the cone filters...super fine screens in the inlet to the hp pump and the vapor separator tank were clogged. He replaced them and the problem was mostly corrected. still stumble a little bit at higher than 4000 but now I don't really lose any rpm, but my ff goes up. i will probably change the hp fuel filter and see if it helps
DT225 drops rpms at 3500
Linear Mode
