Our fl 350 went nuts last night. We have had it about a year and it ran great. As my son pulled into the driveway, the Engine started to rev high. He was afraid of running into something, so he kicked it into neutral. The Engine took off and went WFO. Pulled the key and hit the kill switch and it still ran WFO. Pulled the spark plug wire and it still was running. I finally pulled the choke and it died. Anyone ever have this happen before? I can't believe it still ran after pulling the plug wire. We put a K&N filter on it a couple of weeks ago, but it ran fine until last night.

You turned it into a diesel Engine, well sorta, ever seen a COX Engine for hobby air planes, you hook the battery to them to heat up the glow plug then it starts and runs, no spark...


You might have a air leak that over heated the Engine to the point it was self igniting, carbon buildup inside the Engine can do the same thing, the carbon gets hot and keeps igniting the fuel air, pulling the choke gave it more fuel and cooled the Engine down enough where it would not self ignite any more, poor quality fuel might have caused it to slightly detonate and over heat to the point of self ignition.

The best thing to do would be to pressure test the Engine to ensure you have no air leak , if its tight and not leaking then remove the top end for inspection and to remove any carbon.


Could old, bad, cheap or low octane fuel be a factor here?

If the Engine was already running on the lean side prior to the k&N, then the addition of the K&N could cause it to run leaner creating the problem that you had. This would be especially true if you removed the stock air box and filter assembly and strapped the K&N directly to the carb or carb boot and did not change the jetting.

The fuel was only a week old and it was the same stuff I ran in my truck and two other four wheelers with no problems. The airbox is still there, just with the K&N inside. Thinking back on it, I may have forgotten to put oil on the filter. Would that make it that lean? Thanks for all the suggestions.

I doubt no oil on the filter is your problem, I would look deeper for an answer as discussed above.

If your going to run K&N filters please read this first, maybe you already have?

http://pilotodyssey.com/PO/viewtopic.php?t=3210