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I have a  (late) 2006 model 3000esi. I travel to eastern wa often where the temps can run from mid 70's to 100f. The problem is after a hot soak, the engine will not start.....It will turn over and "run" but it chugs, will not reach a normal idle speed. The plug fires, reves the engine speed up slighty, then stops firing, and only as the engine speed reaches very low rpm, then the plug fores again increasing engine speed, but spark goes away.

I am an ASE master tech with 21 years experience but this failure baffles me. I have verified the problem occurs hot only, and also that spark is going away, or is very weak....used a spark tester and as the engine fires once and rpm increases, can see spark become very weak, and at times goes completely away....then fires again.

Based on my automotive experience I went after the ignition coil....ran through all the Yamaha tests, resistance checks etc, and thought it tested out of specs, wasn't cause to condemn. However i replaced the coil and problem seemed to be gone, but upon first use in high ambient temps and after a hot soak, problem still existed. Looking at the service manual and wiring schematic, there are ONLY two components that control of affect spark. The ignition coil, and the "rev limiter"/ control unit, which is a simple circuit board with capacitors located behind the electrical panel.

On a hunch, i accessed it and used a heat gun to gently heat it up, and compressed air to cool it down....Like a light switch i was able to confirm, it was causing spark to go away when heated, and would begin functioning when cooled...I thought for sure i nailed it as these test results were repeatable over and over.

I ordered a new rev limiter which for an unknown reason was updated and installed it. Just got back from a trip and same problem.  I installed a cooling fan v=from a computer and relocated the rev limiter to in from of the engine cooling fan and went on another trip....turned out to be worse as it was really heat soaking after shut down.

Sorry for the long post but wanted to be accurate as i am really looking for a KNOWN FIX....not guessing and such......can anyone help? ideas? known repairs? updates etc? my dealer says they've never even had one in at all ever for any issue......why the updated rev limiter? is it possible i got a bad one?  I'm at a loss but rely on my gen as i do remote desert camping and need to be able to rely on it!

Thanks a bunch