Hi Morganeers,
I know there is a long and exhausting thread on this topic (
https://www.talkmorgan.com/ubbthreads.php/topics/757598/1 ) but I wanted to make my own long and exhausting post on my recent experiences.
I have had three instances of my M3W not returning to idle after accelerating and I have come to the conclusion that it was the injectors potentially being contaminated that was causing the problem.
I run 98 octane fuel which in Australia is sold as a premium fuel with various additives including a fuel system cleaner.
Typically the engine would remain at high rpm for a few seconds and then decay to idle at a slow and steady rate.
This time I also noted that it would start to decay and then all of a sudden, drop back to idle. Imagine the sound of a poppet type valve suddenly closing and RPM dropping rapidly.
Now there are not many springs in the fuel system and I had thoroughly checked the throttle cable and found nothing out of the ordinary.
Now this comes at the same time that Australian authorities had removed some of the fuel quality control provisions in order to deal with the lack of fuel availability caused by the current USA/Iran war.
A friend who races bikes has said that the 98 octane fuel has been terrible of late and it got me thinking that the fuel injectors (which typically utilise springs in their operation as a return mechanism for the pintle) could be affected by dirty fuel.
I put a bottle of fuel system cleaner in a full tank and after about 90km, all trace of sticking at high RPM has disappeared.
I suspect that with an injector sticking partially open, even with the reduced throttle position, additional fuel could be leading to the high rpm I was experiencing.
I hope that makes sense (and not too long and exhausting topic as I thought it might be)
Cheers,
Paul
