Idle switch

[1springer]

Just had the 04 RT (21.5K miles) in for a tune up. Everything was fine...except he said he "could not check the TPS, the idle switch would not tun off". Other than the switch or wiring what else could it be?

[dirtrider]

Afternoon 1springer

 

Your 04 1150RT doesn't have a MECHANICAL idle switch. The idle switching is internal to your fueling computer & done electronically by using the LEARNED TPS (Throttle Position Sensor) position.

 

Without further info on what your tec was seeing or thinking he was seeing there is really no way to advise you as we really don't know under what circumstances he was getting or seeing that problem. For all we know the tec had the wrong bike model entered in his computer.

 

A few guesses on my part would be:

 

The choke was partially on or the cable mis-adjusted & your tec didn't catch that.

Or

The TPS is malfunctioning.

Or

The TPS is grossly misadjusted & your tec didn't check that

Or

There was no TPS re-learn done after last battery disconnect & your tec didn't do one to verify.

Or

Your tec doesn't know how to use his equipment.

Or

??????????

 

[1springer]

We checked #1 and ruled it out.

We did disconnect the battery and do the relearn.

He does all the work on the police RT's so that's not likely the problem.

 

So that leaves a problem with the TPS or I suppose he could have entered the wrong model number. But I would think if it was a wrong model number other problems would have arisen.

 

Where is the TPS?

[dirtrider]

Afternoon 1springer

 

It (the TPS) is on the L/H (shifter side) throttle body bolted on the outside with 2 small screws.

 

Something to think about-

 

-Your TPS is working (at lest somewhat decent) or you wouldn't be able to ride the bike.

 

-The electronic idle switch is working at idle or the engine wouldn't be able to idle (would be in fuel shut off).

 

-If somehow the electronic idle switch wasn't working on engine deceleration that would be like winning the lottery as you would not have that darn fuel shut-off on dropped throttle. That alone could make the bike run a whole lot better at light throttle on dropped throttle decel.

 

[1springer]

Thanks.

 

Good point, the bike seems to be running fine. Hmmmmm.

[AndyS]

I am confused...

Just had the 04 RT (21.5K miles) in for a tune up. Everything was fine...except he said he "could not check the TPS, the idle switch would not tun off". Other than the switch or wiring what else could it be?

Are you saying you have a problem? I can't see one.

If the bike had a service, you wouldn't be checking the TPS.

If the bike is running well, you wouldn't look at the TPS.

What gives?

Andy

[roger 04 rt]

While I was taking data using a GS-911 during the early parts of my Wideband O2 Sensor Project, I mapped out the TPS. Here is a link to some data on that: TPS Angles.

 

When you calibrate the throttle after a reset, assuming the cables are adjusted correctly and the Fast Idle lever was off at the time, the Motronic computes the following:

 

--Lowest Voltage (idle) is reported as 0.32 degrees (whether it is mechanically set there or not).

 

--Highest Voltage (WOT) is reported as 80 degrees

 

--If you twist the throttle about a degree off idle using either the throttle or Fast Idle lever, the Motronic reports that the "fast idle switch" is on. On my bike Motronic reports 1.28 degrees when the Fast Idle lever is up.

 

--On trailing throttle deceleration, the Overrun Fuel Cutoff function kicks in when the throttle is 2 degrees open or less and the injectors are not squirted until: a) the engine speed drops below 1800 RPM or b) until you crack the throttle more than 2 degrees open.

 

If your mechanic or you has a GS-911 or equivalent you can verify this data and maybe figure out what's going on.

 

...

 

-If somehow the electronic idle switch wasn't working on engine deceleration that would be like winning the lottery as you would not have that darn fuel shut-off on dropped throttle. That alone could make the bike run a whole lot better at light throttle on dropped throttle decel.

 

You probably remember that I mapped the Overrun Fuel Cutoff a few months back. I agree that it can be nasty at times but I found that since I've known just where it kicks in, it is less annoying, sometimes even an advantage.

 

I think an EE could design a circuit to go between the TPS and connector, which would delay the drop below 2 degrees by a time so that it didn't get accidentally triggered. Calling all EEs.

[dirtrider]

 

 

You probably remember that I mapped the Overrun Fuel Cutoff a few months back. I agree that it can be nasty at times but I found that since I've known just where it kicks in, it is less annoying, sometimes even an advantage.

 

I think an EE could design a circuit to go between the TPS and connector, which would delay the drop below 2 degrees by a time so that it didn't get accidentally triggered. Calling all EEs.

 

 

Morning Roger

 

Yes an electronic delay would be nice. A mechanical would also work.

 

When I was working with the older 1150's Ma 2.4 systems I had always wanted to install a mechanical dash pot (lots older cars, trucks, & some bikes used mechanical dash pots).

 

A good dash pot could be set up to stop the dropped throttle at just above fuel cut off then slowly allow the throttle to close into the full idle position. That would delay fuel shut-off on a quickly dropped throttle & make low speed throttle modulation & dropped throttle over run much less abrupt & much smoother.

 

BUT- One of the issues on delaying or stopping fuel shut off on dropped throttle is severe after burn popping in the exhaust system on dropped throttle.

 

Two basic ways to stop or reduce afterburn popping.

 

One is to shut all the fuel off so there is nothing to ignite in the muffler on dropped throttle (like the BMW's)

 

Or add a high vacuum circuit to add extra fuel on closed throttle dropped throttle (like the older Honda systems).

 

Guess which one gets the best fuel economy?

 

 

[roger 04 rt]

Morning DR,

 

The dashpot idea sounds good but maybe a bit hard to mount well. Any thoughts on where one could go and how it might be mounted?

 

You mentioned popping but I often drop the throttle to just above the point where it goes into Overrun Cutoff and I don't get any popping. Am I just lucky or is it the slightly richer mixture I'm running do you think?

 

RB

[1springer]

I am confused...

Just had the 04 RT (21.5K miles) in for a tune up. Everything was fine...except he said he "could not check the TPS, the idle switch would not tun off". Other than the switch or wiring what else could it be?

Are you saying you have a problem? I can't see one.

If the bike had a service, you wouldn't be checking the TPS.

If the bike is running well, you wouldn't look at the TPS.

What gives?

Andy

 

Taking into account my meager understanding of the electronics of the RT and the diagnostic program used, what I'm being told by the mech. that did the work is that

the diagnostic program used indicated an (for lack of a better word) out of spec condition associated with the TPS something to do with the voltages involved.

 

As far as why he is checking the TPS, I'm assuming it is part of the program used. Since he does all the maintenance work on the police departments 1150 and 1200 RTs I'm also assuming it is a "standard BMW program".

 

Now with regards to wether there is a problem or not, if a parameter is out of spec. and unable to be corrected something is amiss what ever the reason. The question is what and if it is a mechanical/electronic problem I want it fixed. Especially since I don't know what the long/short term ramifications could be. Very important when your out riding in the middle of nowhere and there is a lot of nowhere in the western U.S. and Canada.

 

[dirtrider]

Morning DR,

 

The dashpot idea sounds good but maybe a bit hard to mount well. Any thoughts on where one could go and how it might be mounted?

 

You mentioned popping but I often drop the throttle to just above the point where it goes into Overrun Cutoff and I don't get any popping. Am I just lucky or is it the slightly richer mixture I'm running do you think?

 

RB

 

 

 

Afternoon Roger

 

I gave it a bit of thought years ago as I had a couple of adjustable dash pots in a box I found in my shop attic.

 

One thought was to just place it on the L/H TB to keep the TPS voltage above fuel shut off & just let he R/H side go back to idle. It would only be a bit uneven but not under load so the fueling difference probably wouldn't matter.

 

The other though was to mount the dash pot to the bowden box & have it retard the cable pulley evenly for both sides. I don't even know what this would involve.

 

I had a set of Webber carbs on a Porsche years ago that had a dash pot on each side so maybe that would work on the twin TB's.

 

The other thought (only a quick thought with no follow up) was to add a 2nd lever to the TPS & have the dash pot only retard the TPS return to idle not the throttles.

 

Might be able to accomplish the same thing with a vacuum switch & resistor to the 5v TPS input to keep the TPS base voltage a bit high at very high dropped throttle vacuum. Probably use a vacuum switch from an old G.M. (pre sequential inj.) auto trans converter unlock circuit. If the potting material is scraped out they are adjustable.

 

I think the 1200 oilhead used a type of throttle return control.

 

I don't know why yours isn't popping but maybe you are keeping the RPM's high enough & the mixture rich enough to allow combustion prior to the muffler. The big problem comes from closed throttle with a bit of fuel as that won't allow combustion until the fuel finds some air in the muffler. So you either need to make it too lean to ignite (actually no fuel) or make it too rich to light off (lot of older Japanese bikes did it that way).

 

[dirtrider]

---

 

Taking into account my meager understanding of the electronics of the RT and the diagnostic program used, what I'm being told by the mech. that did the work is that

the diagnostic program used indicated an (for lack of a better word) out of spec condition associated with the TPS something to do with the voltages involved.

 

As far as why he is checking the TPS, I'm assuming it is part of the program used. Since he does all the maintenance work on the police departments 1150 and 1200 RTs I'm also assuming it is a "standard BMW program".

 

Now with regards to wether there is a problem or not, if a parameter is out of spec. and unable to be corrected something is amiss what ever the reason. The question is what and if it is a mechanical/electronic problem I want it fixed. Especially since I don't know what the long/short term ramifications could be. Very important when your out riding in the middle of nowhere and there is a lot of nowhere in the western U.S. and Canada.

 

 

Afternoon 1springer

 

We still don't know what your tec is seeing, or using to see what he is seeing, or what circumstances he is seeing it under.

 

If your bike runs good, idles good, & you can feel fuel shut off on dropped throttle deceleration then I would suspect the test equipment used to determine the idle switch isn't working properly.

 

If it was me & I was "real" worried about that data showing the idle switch is not working when it is supposed to I would:

 

First use an analog (needle type) volt meter to verify the TPS is sweeping smoothly full scale on the hi & low outputs. (no dips or oddities in either output). A digital meter probably won't show you what you need.

 

(if that is good)

 

Next make sure there is some slack in the lower throttle cables & the L/H side TB is easily & fully returning to the idle stop screw.

 

Then go by the service manual to properly set the TPS initial position.

 

Then do an R&R #5 fuse for 30 seconds then a new key on TPS re-lean.

 

Then put a GS-911 on the system & see how the Motronic interprets & processes the TPS input & when the idle switch comes & goes.

 

[1springer]

I think your right about the test equipment. As long as it keeps running satisfactorily I'll wait until the 24K service and have it addressed then.

 

Thanks for the input.

[AndyS]

Is 'Soggy Bottom' a real place or a medical condition???

Andy

[1springer]

It's the latter.