Cutting out at very small throttle

[BMWDavid]

My 2002 V11 LeMans with 22,600 miles has recently started to act a bit strange. At very small throttle opening such as cruising about town in 2nd or 3rd gear at 2500 rpm or going down a slight hill at trailing throttle the engine will occasionally cut out and immediately resume normal operation. It will/can do this several times at minute.

 

Bike starts from cold and hot just fine. With any load it will not do this. Pulls hard and clean through the gears all the way to red line. Cruises on the highway (55-75 mph) just fine. Its only at barely open throttle does it appear.

 

Taking off from a stop it will also do the cut out but if I'm a bit aggressive with throttle it will take off fine.

 

Just asking the group for possible ideas before I jump into this.

 

Thanks! 

[stewgnu]

Hmmm, loose batt terminals? Plugs not tight? Crudded up fuel filter?? Split intake rubbers??? You will also be asked when you last checked the tps...

[Kiwi_Roy]

Have you bypassed the side stand switch?

Cleaned the ignition switch?

Do both cylinders cut out?

 

 

Sent from my shoe phone!

[BMWDavid]

I don't believe its an electrical issue such as a side stand switch, battery, etc. It feels more like a fuel shut off...its fairly soft in nature but does jerk the bike when it occurs. The duration is about 1/2 second...maybe a bit less. There is no backfire. It does seem to affect both cylinders at the same time.

 

If it were an electrical issue would it not be random at all speeds/rpm and throttle positions? As mentioned above it only happens at really small throttle openings...barely cracked and does intrude on take off sometimes. As soon as throttle position is more than a few degrees past affected area it is fine. 

 

I thought about the intake rubber boots as there are some fine surface cracks. But wouldn't there be a leanness and backfire on deceleration? 

 

TPS? If it was not set optimally would very small openings be at the first part of the potentiometer? 

[footgoose]

here's a recent thread. not exactly the same, but similar problem. maybe it'll spark an idea. electric of some kind, my guess. I'd start with replacing the fuel pump relay.

 

http://www.v11lemans.com/forums/index.php?showtopic=19501&hl=

[docc]

That's another good thread that puts a finger on all the likely culprits (they're all worth a look and some fine fettling.

 

When my Sport was doing this, I found a few contributors, but a bad TPS made a major difference. I couldn't find it watching the change in millivolts with my meter, but by disconnecting the TPS and watching the resistance in the finer settings, I could see an abrupt *jump* as the TPS opened and closed across a specific point. New Harley-Davidson TPS and big improvement.

 

The rest of that odyssey meanders through this thread spanning seven years: Nasty Hiccup

 

Now, that's a bad case of the hiccups!

 

That said, sometimes a really thorough and complete tune-up is all that it takes.

[Chuck]

 

 

That said, sometimes a really thorough and complete tune-up is all that it takes.

Agreed, but I would suspect the TPS.

[docc]

 

 

 

That said, sometimes a really thorough and complete tune-up is all that it takes.

Agreed, but I would suspect the TPS.

 

Doubly agreed!

[BMWDavid]

Thinking about this and reading over the long thread on the hiccups leads me to think it's my TPS. I can make it occur repeatedly while going down a slight hill on trailing throttle. It will hiccup almost continually but as soon as I roll in a few degrees of throttle all is well.

 

I guess I'll contact Curtis for a TPS.   

[Scud]

I think I have a used one that you can try - to see if that fixes the problem. PM sent.

[Kiwi_Roy]

Wrap nod end of a small gauge wire around the 87 pin of the pump relay run the other end to a small lamp taped to the bars, a flickering lamp will get your attention.

It may well be something else but the little lamp will eliminate one possible cause.

 

If it were a TPS wouldn't it show up measuring the millivolts without the bike running?

[jharvey]

Wear in the bar ends that connect the throttle bodies?  Especially since it's more pronounced while transitioning off of high vacuum situations.

[Scud]

Loaner used TPS on the way for testing porpoises. Keep it as long as you need to in order to isolate your problem.

[docc]

Wrap nod end of a small gauge wire around the 87 pin of the pump relay run the other end to a small lamp taped to the bars, a flickering lamp will get your attention.

 

It may well be something else but the little lamp will eliminate one possible cause.

 

If it were a TPS wouldn't it show up measuring the millivolts without the bike running?

Ah: the Kiwi_Roy Go_Winkie.   It's only on the bars (or anywhere) to be visible if sputtering occurs.

 

I do have one installed, but am admittedly vague on what it isolates.

 

I could never catch my TPS glitch (potentiometer worn at a singular point) watching millivolts on my Triplett meter. Yet, it was really obvious watching resistance as I opened and closed the TPS - always jumped at the same opening.

[Kiwi_Roy]

The schematics all depict the TPS as a simple potentiometer, It's not.

It doesn't Ohm out like a normal potentiometer.

I suspect it has another set of resistors that cause it to default to a fixed mV value if the slider loses contact.

 

You can buy a Hall Effect device now to replace the TPS (no sliding contact to wear out)