Hiya team. I'm running out of things to try to get this engine running correctly and it's driving me insane. It is a 2007 150hp VMax with about 700 hours. I've owned it for a year. When I first got it, there was a really minor, almost imperceivable, flat spot during acceleration. I assumed at the time it was a dirty filter or something simple maintenance related. Well, turns out it's continuing to get worse even after addressing all of the basics.
Essentially when I go our first thing, she starts right up and idles fine. However when I go to accelerate, it will start to rev to 900-1000 and then will not increase further. If I continue to push forward on the throttle, it will either accelerate in really jerky patches until I get close to half throttle, or it leans out and stumbles. If I can get past about 1/4 throttle, it seems to pick up and run pretty well. Maintaining 1/2 to full throttle all seems fine. It's worth noting that when it's acting up, which is every time now, that if I move the throttle back and forth, it seems to accelerate in inconsistent jerky spurts. Moving the throttle back and forth quickly helps get it through its fits. The issue also seems to subside a bit after the engine has been run and warmed up but still very noticeable.
So far, I have replaced the spark plugs, all mystery filters including the injector baskets, medium pressure filter, VST filter and internal pump, both low pressure pumps, replaced fuel lines and filters from the engine to the tank. Aside from the high pressure pump and injectors everything in the fuel system has been replaced. I've also been testing the throttle position sensor since that seems like a logical issue if that had any flat spots. I can't find any with a multi metre.I have a very clean 5.0V signal and 0.61V at idle with a max of 3.6V at full throttle. I've gone ahead and ordered a new one anyways just to test that theory. I have also tested the throttle switch, it seems to switch just fine as soon as I move to F or R, only odd note on this one is that I'm getting 10.6V across the switch instead of full battery voltage.
I'm open to ideas team. This one has me stumped. For the life of me it seems electrical since the engine can run from half to full throttle and maintain full speed. In my experience fuel issues get worse with RPM.
Essentially when I go our first thing, she starts right up and idles fine. However when I go to accelerate, it will start to rev to 900-1000 and then will not increase further. If I continue to push forward on the throttle, it will either accelerate in really jerky patches until I get close to half throttle, or it leans out and stumbles. If I can get past about 1/4 throttle, it seems to pick up and run pretty well. Maintaining 1/2 to full throttle all seems fine. It's worth noting that when it's acting up, which is every time now, that if I move the throttle back and forth, it seems to accelerate in inconsistent jerky spurts. Moving the throttle back and forth quickly helps get it through its fits. The issue also seems to subside a bit after the engine has been run and warmed up but still very noticeable.
So far, I have replaced the spark plugs, all mystery filters including the injector baskets, medium pressure filter, VST filter and internal pump, both low pressure pumps, replaced fuel lines and filters from the engine to the tank. Aside from the high pressure pump and injectors everything in the fuel system has been replaced. I've also been testing the throttle position sensor since that seems like a logical issue if that had any flat spots. I can't find any with a multi metre.I have a very clean 5.0V signal and 0.61V at idle with a max of 3.6V at full throttle. I've gone ahead and ordered a new one anyways just to test that theory. I have also tested the throttle switch, it seems to switch just fine as soon as I move to F or R, only odd note on this one is that I'm getting 10.6V across the switch instead of full battery voltage.
I'm open to ideas team. This one has me stumped. For the life of me it seems electrical since the engine can run from half to full throttle and maintain full speed. In my experience fuel issues get worse with RPM.