I'm sharing an experience that I recently had with my M4-071 (170hrs). Last year while pulling a big aerator it seemed the tractor was losing power. At the time I chalked it up to the weight of the implement and didnt think much more about it. This summer I was mowing with a 6-ft hog and it happened again. Its a light mower for that tractor, so I could not blame implement drag. I checked to see if there was something fouled in the blades and it was clean. It was an intermittent problem but with end of warranty nearing, I had it checked by the dealer. They found it was making only 38HP on the dyno. After several more diagnostics, they ended up changing the 4 injectors. Post-repair dyno testing showed it making 65HP. Fortunately, the $7000 repair was completely covered under warranty. Once the tractor was back I noticed a significant change in the sound of the tractor - it's louder. It also seems to have a higher RPM at resting idle which may be why it seems louder. Finally, there is a HUGE change in regen frequency. Prior to the fix, the M4 required a regen every 15-18 hours - which was a huge hassle and not in line with typical reports of 30 hours for a regen. (sidenote: the dealer said 15 hrs is within the regen frequency spec). Since the repair, the particulate gauge is at 33% after 15 hours, so about a 3X difference. Thought you might like to know.
