Sputtering, uneven power delivery

[Parkblu]

My R* has since approx. 4-6 months slowly developed some problems I can't nail:

- it runs lumpy in idle and in slow rpms up to approx. 2,500rpm
- it backfires on downshifts and sometimes also upshifts
- when opening the throttle wide in any gear, it delivers power unevenly and even hesitantly, with nearly always a surge north of 5,500rpm as if it finally runs freely.

What could be the reason (or reasons) ?

Thanks and Danke!
-tobias.


*'04 twinspark, 12k mi, warranty until June 2006, bought used with 3k mi, 12k mi service done, Remus exhaust + cat-ex since 4k mi or 12+ months

[jimcameron]

The reasons could be many. You just had the 12k service done by a shop, or did you do it yourself?

Your using premium grade petrol or 87?

Did the problem start at the same time as the 12k service?

More details needed.

ride on.
jim

[ranmar850]

Look for a major air leak on your intake tract somewhere...

Just a hunch

[Parkblu]

The reasons could be many. You just had the 12k service done by a shop, or did you do it yourself?

Your using premium grade petrol or 87?

Did the problem start at the same time as the 12k service?

Jim,

- service was done by a shop (441 BMW in Fort Lauderdale, FL)
- always use premium petrol
- that's a good question - I'm trying to remember if the problems started with the 12k service. I can't quite piece it together, but it could be.

What do you suspect?

[fnfalman]

Could be that your valves are in need of adjustment and the throttle bodies out of synchronization as well. My rockster didn't have any backfiring on the acceleration but did have some on the decel. And the acceleration was a bit hesistant as well. Done the valve adjustment (both the intake and exhaust valves were loose) and synch the throttle bodies and how she purrs like a happy cat and I can definitely tell a big difference in acceleration. It's much snappier and revvier now.

[GeoffJ]

Another possibility is a defective lambda (oxygen) sensor.

[Parkblu]

Could be that your valves are in need of adjustment and the throttle bodies out of synchronization as well... Done the valve adjustment (both the intake and exhaust valves were loose) and synch the throttle bodies and how she purrs like a happy cat and I can definitely tell a big difference in acceleration. It's much snappier and revvier now.

First, many thanks for the feedback so far!

Between those possibilities (incl. the lambda sensor) this looks like a dealer-task to me.

Being under warranty for a few more months and not having the tools, I'm going to call the two nearest shops (Fort Lauderdale where I am; typical waitlist 4 weeks plus; and Bee Emm in Fort Myers, about an hour's ride, good reputation) and see how soon someone can take a look at it. I'll post an update as soon as there is interesting news.

[Parkblu]

I got a service appointment Sat in a week and will let y'all know how (and if ) they rescued my moped.

[Parkblu]

The problem is solved, the bike had leaky ignition coils. BMW of Fort Myers, FL, replaced them (under warranty, yeah), checked throttlebodies and valves (all fine they said), and I'm happy to report she's back to normal.

Needless to say, I didn't leave the shop without some financial damage - I was due for a new front tire soon, so I bit the bullet...

Thanks everyone, for your input and comments!