Engine 60k miles year 2002
Plugs 15k miles (Iridiums – good for 32k)
Engine regularly serviced
Just happened this morning. Noticed a different ‘burble’ when slowing down for traffic & then the engine was erratic up to 3500RPM on small throttle openings. Sounds & feels like its dropping a cylinder most of the time but the odd time it kicks back into life. The idle speed has also dropped & is jumping from 1000 – 1300 RPM. Engine runs well as even above 3500 RPM & you would not know there is any problem.
Hi King Kenny, I have the same thing happening with my 929. It started at approximately the same mileage. The idle went unstable and engine started stuttering badly when riding off the trafic lights, junctions, etc. It's happening below ~3500 and seems to be fine above that. I have replaced the spark plugs and it helped... temporarily.
Thing is I was unable to get the Iridium plugs for replacement at that moment (I was visiting Isle Of Man TT, checked all the shops/dealerships on the island with no luck), so I put "conventional" CR9EH-9 plugs, which had completely eliminated the problem for that time. Mind you, not single of the replaced plugs seemed to look like the cilinder has been misfiring or anything, they were all brown/grey color no deposit, etc.
In 1000 kms (~600 miles) the problem reappeared again and went really bad on my way back from IOM. I'm not sure if it is still because of the "wrong" type of plugs so I am replacing them with a set of Iridium ones today and will let you know if it hepls.
The only other thing I can think of is an ignition coil "killing" the spark plug somehow (which I've never heard of before).
Or could it be the valves?