Stumble - Hesitation on Gen 1 Busa

kissos

Registered
Anyone with more experience that I offer suggestions for a Gen 1 2006 Busa with no engine mods except for a K&N air filter and a Scottoiler (vacuum switched auto chain oiler).

Recently around town rolling off the throttle and then accelerating gently can result in a stumble or miss fire at about 2000 rpm. She misses once or twice and then pulls away normally. It only happens in 3rd not 2nd or 4th just 3rd gear. Its slightly worse under load ie going uphill, and when warm.

No other symptoms and she runs like a train otherwise. She starts first time when cold but has always been a pig to start when warm, which is probably a red herring. Tickover has always been a little lumpy but assume this is normal.

I've changed the plugs, centered the TPS, and balanced the injector bodies all to no avail. There are no error codes in Dealer Mode.

I figure (so am probably wrong) that its not a fuel pump/filter issue as there is plenty of power, ditto a spark issue.

Sounds like it might be a vacuum problem as the fault is between the overrun and throttle.

Any ideas on what this can be and what test to run??
 
might be an injector getting lazy..... don't worry.. itll get worse and easier to identify.....
 
Thanks for the advice and the problem is fixed. It was a vacuum issue, I noticed that the vacuum pipe to the airbox actuator was off. Simple and frustrating that I didn't see that earlier. After refitting she was back to normal.

I can't sit here smugly congratulating my brilliant diagnostic skills as I probably left it off at the last service!

I do like the video of the injector cleaning fluid, powerful stuff, and I will give that a try to see if it helps with the warm starting issues.

Thanks again.
 
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