2005 RXT Engine surges at half throttle.

[Mainely-French]

Any Ideas why I have a fluctuation in RPM's while at around half to 3/4 throttle? The fluctuations are about 1000 RPM's. While this is happening, I go to WOT and it seems to drag a few seconds then gets to top end. Immediately after backing down the speed, it seems to run smoothly for near 30 seconds, then surges again.

I bought it used last year. The washers were replaced and the S/C was rebuilt around 55 hours. It has 75 hours now. I had the wear ring, impeller, and the idler valve replaced (would not idle on it's own) this year and ran fine 3 times out. I just replaced the plugs yesterday but will not be out till next weekend.

Thanks,
Rick.

 

[red2blue]

injectors?

 

[Michael211_2000]

Did you treat the fuel before storing for winter with some stabilizer? Your fuel may have gone bad over the winter months if not! Sounds like it's having a hard time getting fuel to the injectors to me. You could try treating the tank with SeaFoam and see if running it some more won't clean it out.

- Michael

 

[Mainely-French]

Thanks for the replies. I tried injector cleaner, and have been treating the gas with ethanol treatment (Lucas Oil brand), changed the plugs, but still has the same symtoms. I have run it 4 times since my last post, app 20 hours. I am leaning on a bad injector? Are replacing them very difficult? Is it difficult to detect which injector might be bad?
Rick.