sputter and die return to idle

[canoehead]

I have an occassional problem with my R1100R dying when I roll off the throttle from highway speed. Most noticable when the engine has only run a short time, but it has happened at other times. I attended one of the tech sessions at beemerville (very helpful) and came away with the suggestion that valve setting was the most likely culprit. I've started to implement the tuning suggestions from the tech session, one at a time, to see if I can pin it down. When I pulled off the valve covers, the clearance was just about perfect on all valves. One was a snick tight, another was a snick loose but all were very close. Riding the bike after bring all valves back to spec showed no change. One spark plug was in a little worse shape than the other when I pulled the old ones out. A new set smoothed the engine out a lot in the 4,000 rpm range, but didn't fix the sputter and die. I haven't set the TPS yet but did do a TBS which also helped smoothness. Haven't checked timing yet. Any suggestions on what I should concentrate on?

[bmwmick]

Rolf,

Bring the idle up to 1,100 and see if it still fails.

 

Mick

[canoehead]

Rolf, Bring the idle up to 1,100 and see if it still fails.

I'd already done that. Both my wife and I have R1100Rs. Mine seems to "hunt" for a steady engine speed at lower revs when compared to hers. That makes me think it's probably TPS. However, I have noticed sometimes that it feels like a misfire of one cylinder preceding the die, so I wonder about timing or hall effect. I haven't noticed any indications of timing problems except for that situation described.

[ShovelStrokeEd]

Rolf,

 

Good chance your fuel pressure regulator is acting up. Its probably getting slow to respond to changes in demand. So, there you are, running down the highway, happy as a clam at 4K RPM and you shut the throttle. Fuel pressure will spike high under this condition and it might be faster than the regulator can compensate. Pressures over 60 PSI (4 bar) will cause the injectors to stop firing.

 

The other possible culprit is your throttle position sensor. It might have a dead spot, but this should evidence on the way up as well as down.

 

I doubt valve adjustment has a thing to do with it.

 

The last thing you might look at is the charcol cannister plumbing. If it is not connected correctly, your tank may not be venting properly. The diagrams at the MAX BMW site may prove helpful.

[canoehead]

Thanks Ed

Hadn't thought of fuel pressure, but your description make sense and symptoms fit. Is that something that can be tested by a home mechanic? Is it anything to worry about or just live with it in a machine that works fine otherwise? I'm now in the habit of rolling of the throttle more slowly and it's rare the bike stalls.

 

Canadian bikes didn't come equiped with the canister, so that's not an issue.

[ShovelStrokeEd]

Well,

 

Depends on your definition of home mechanic.

 

The TPS thing only needs a voltmeter. I don't have a schematic handy but I think the output is the last pin on the right as your looking at the unit. A simple voltmeter should resolve that. Should be <0.400 volts at idle and smoothly rise from there.

 

Fuel pressure can be done as well, it just takes more work. Tank has to come off and then you tee into the line between the pump/filter and the pressure regulator. Observe pressure while riding under load. Nominal is 3 bar. While your under there, check and make sure the return line is free. There should be no restriction.

[scottfarm2]

Mine is doing the same thing. I changed the tps off another bike and it still does it. When I blip the throttle it will misfire or sputter. If I ease the gas to it its fine. When I blip the trottle the idle will go down to 950 and then slowly creep back up to 1200. Some times it will go dead just like yours if I roll off the trottle to quickly. Let me know if you find the cure. My 94RRS does not do this. It is driving me crazy not being able to figure it out.

[canoehead]

Well, Depends on your definition of home mechanic.

I apprenticed as an optical instrument technician and used to do all my own wrenching on two stroke competition dirt bikes. Boxers are different than either of those former experiences but I'd think much of the skill and knowledge would be transferable. I'm learnin...

 

Fuel pressure can be done as well, it just takes more work. Tank has to come off and then you tee into the line between the pump/filter and the pressure regulator. Observe pressure while riding under load. Nominal is 3 bar. While your under there, check and make sure the return line is free. There should be no restriction.

Ed, I'm a little unclear on the above. If I put the tee where you suggest, that'll give me an indication of what the pump is doing but it won't tell me what the output of the regulator is, or can I tell that from the readings upstream of the regulator? I haven't looked yet, but I'm assuming I should be able to figure out where the regulator is by following the lines? Should be an electrical device with two fuel lines connected?