Sticky throttle somewhere I can't find

[benebob]

My 885i has started sticking a bit when you push the clutch in to shift (i.e. the revs aren't quite done).  I pulled apart the throttle and cable lubed it up good and checked for anything holding it up and everything seems good.  Any ideas out there?  Was hoping to make it to winter before having to tear apart the bike as my 24k service should be right around christmas.

[Bixxer Bob]

Are you saying you think the throttle is sticking because the revs don't drop to tickover?  If so you need to find the problem sharpish. A stuck throttle is no fun (believe me' I've had that!)  In my case it was a badly fitted Scottoiler vacuum T getting in the way of the throttle linkage.

Take the tank off  (10mins) and the airbox and have a good furkle around, check the cable seats, cable outer for kinks or tight spots, throttle stop adustment screw, throttle slack adjuster etc etc

[iansoady]

Could also be stuck IACV / split pipe?

[Bixxer Bob]

Possibly, although more likely that would cause rough tickover and cutting out.

[benebob]

What it's doing is say I release the throttle and push in the clutch to shift.  The rpms are still rising by the time I let the clutch out again.  Just a little run over.  If I granny shift and hold the clutch in for 3 seconds or so then the rpms drop down to idle.  Seems to be doing it in the 2k-4k rev range.  Above that I don't seem to notice.  Also if you blip the gas in neutral you can be completely off the gas and it'll still be rising before dropping down a few seconds later.

[Bixxer Bob]

Something is causing the IACV to lag behind the throttle position i.e. the ECU is holding open the IACV momentarily for some reason when the throttle is shut.  I don't THINK it'll be stuck because she wouldn't idle if it it was. Same goes for an air leak, tickover would be lumpy.  I'd be looking for something like blocked air filter and nipped or blocked baro tube. Both could cause the ECU to see a depression in the airbox  which the ECU will respond to by opening the IACV.  If it was a U/S sensor there'd be fault codes and maybe the MIL light on.  Other than that I've not come across this before without lumpiness or cutting out.  Except one time it happened when I'd been messing with the low revs end of the fuel map.  And another when I had a corrupt map.

[benebob]

Something is causing the IACV to lag behind the throttle position i.e. the ECU is holding open the IACV momentarily for some reason when the throttle is shut.  I don't THINK it'll be stuck because she wouldn't idle if it it was. Same goes for an air leak, tickover would be lumpy.  I'd be looking for something like blocked air filter and nipped or blocked baro tube. Both could cause the ECU to see a depression in the airbox  which the ECU will respond to by opening the IACV.  If it was a U/S sensor there'd be fault codes and maybe the MIL light on.  Other than that I've not come across this before without lumpiness or cutting out.  Except one time it happened when I'd been messing with the low revs end of the fuel map.  And another when I had a corrupt map.

Idle and running is just fine, fuel mileage is around 200mpt with nearly all my 2 mile to work commute so I'd not think the air filter is shot though I have 21k or so and no clue if it has ever been replaced.  No light on so no code right?  What is the baro tube?  Also would it do anything to have it relearn by starting and letting it idle?


Also, looking at my service manual jogged my memory on something.  When I was checking everything around the cable last night I noticed that the fuel pressure regulator wasn't attached to anything.  There was a vac or breather line just laying in there not connected to anything on either end so I hooked it up to the FPR.  The other end isn't attached to anything and looking at the book I know that should be a vac line now not just a breather so where does that attach to?  I don't think this is the root of my problem though as I don't see how both ends would just magiclly detatch...  I'd suspect it hasn't been attached for some time.

[metalguru]

Just a breather pipe on the FPR for the pressure regulating diaphragm and can be linked to the airbox or left off.

With BB on this too only thing different to check would be the throttle body balance, check to see they are clean around the flaps (ooeerr), the choke flap pivot is not stiff and the return springs are clean and lubed and the air filter is clean. Wouldn't hurt to lube the IACV but DON'T use WD40.