Idle rpms too high

[Tsiklonaut]

So I did the zero-zero procedure. I've done this before successfully but this time my idle rpms are too high, around 1250 rpm with both idle screws fully in. TPS is set to the usual 0.375 V, TBs are synced, but just can't tune down the idle rpms since idle screws are completely in and run out of adjustable range.

What do you reckon can cause this - air leak, loose butterflies, bad TPS?

 

[Smug]

An air leak would cause a fast idle. Check by squirting something like brake cleaner in the areas where one might expect a leak to see if it affects the idle speed.

 

[uncle dick]

Probably a worn throttle body confusing the zero-zero procedure. Try backing off the throttle stop screws an equal amount, reset the TPS voltage then see if the air screws do their job.

 

[(RIP) Kaister]

Can only be an air leak on a slightly rich mixture...try weakling the TPS to get the idle down ...then you'll know

 

[MattW]

As others have said, it's got to be air leaking in somewhere during the zero-zero. Tricky to do but can you eyeball the throttle butterflies and see if they're approximately equal when on their stops?

 

[Tsiklonaut]

Cheers guys!

Still work in progress...

Did a proper visual test, the butterflies on both sides seem to be allright and pretty much near perfectly closed.

I'm starting to wonder if a bad lambda sensor signal mess things up like that? I suspect this might be a possible cause - over biased lambda (dirty?) feedback making the mixture maybe too rich on idle(?) It's probably not out of range since Motronic didn't gave any fault code on oxygen sensor, but mayb could be off just enough to cause richer mixture.

Motronic did return me "1215" code, which means a bad TPS, it was because after that code I found the left stop screw had come loose last week and it dropped way below 0.370 volts while on the road. Maybe it somehow damaged TPS since I rode quite some time forced to use choke to keep up idle rpms (stalled during gear changes ). Hence the original reason doing zero=zero procedure this time again.

After zero=zero I did reset Motronic and it returned the normal "4444" code which means everything's now allright (no faults stored in Motronic memory), but as said, it idles a bit too high at around 1250 rpm even with air-screws fully closed.

I do have a spare s/h TPS unit somewhere, might try another TPS unit just in case as well.

 

[uncle dick]

Cheers guys!

Still work in progress...

Did a proper visual test, the butterflies on both sides seem to be allright and pretty much near perfectly closed.

I'm starting to wonder if a bad lambda sensor signal mess things up like that? I suspect this might be a possible cause - over biased lambda (dirty?) feedback making the mixture maybe too rich on idle(?) It's probably not out of range since Motronic didn't gave any fault code on oxygen sensor, but mayb could be off just enough to cause richer mixture.

Motronic did return me "1215" code, which means a bad TPS, it was because after that code I found the left stop screw had come loose last week and it dropped way below 0.370 volts while on the road. Maybe it somehow damaged TPS since I rode quite some time forced to use choke to keep up idle rpms (stalled during gear changes ). Hence the original reason doing zero=zero procedure this time again.

After zero=zero I did reset Motronic and it returned the normal "4444" code which means everything's now allright (no faults stored in Motronic memory), but as said, it idles a bit too high at around 1250 rpm even with air-screws fully closed.

I do have a spare s/h TPS unit somewhere, might try another TPS unit just in case as well.

It won't be the lambda sensor.

 

[Tsiklonaut]

With another TPS unit it was the same if not worse. I noticed with both TPSes that they had to be turned almost completely out to find the zero voltage during the procedure, thus I'm now starting to suspect the throttle bodies themselves, probably worn out indeed. I did installed Dan Cata TB overhaul kit some 6000 miles ago so the TB shafts should be good, but the original butterflies had to be re-installed and those could be worn since they're the ones limiting the TBs "closing angle" the TPS sets zero voltage on.

Also I noticed with another TPS unit that RPMs tend to vary a bit, up and down, from 1100 to 1500 rpms on idle. Motor was acting odd, but could be that my spare TPS that has stayed on the shelf for years just had corroded contacts and thus maybe an electrical issue. I put back the original TPS, zeroed it and it was much more stable running again, albeit still high at around 1200 rpms.

Could a leaking intake valve do this?

I reckon I'll just have to go below the standard 0.37 volts with the TPS to fix this for now, and re-sync the r/h TB accordingly.

 

[monkeyboy]

Wish I could get mine to idle at 1250. I'd be happy as larry! I can't get mine above 1k.

As for the lambda effect - IMO the lambda plays a big part. I was reassembling the bike after changing a head at the weekend and forgot to plug the TPS back in. The bike runs, you can rev the throttle (very gently else it just dumps but it will rev right out if you want) and you can even ride it if your're careful. All that is because of the lambda effect and it adjusting for the mix. I still can't get the zeroing right either. I'm getting a new pair of BBSs as the orings have swollen over time and you can't buy them seperately. They're only about £4 each anyway. Unscrewing one of them has pretty well no effect on tickover until the oring clears the throttle body

 

[Roger 04 RT]

If the idle speed won't come down, there is too much air entering. The butterflies are most likely open more than you think.

Think about it. Normally to change idle speed you add or remove air.

Other than that, what Coding Plug do you have installed?

 

[Tsiklonaut]

I have the normal pink CCP with the engine working in lambda-mode "closed loop" configuration - this has always worked the best for me in terms of overall smoothness, no surging and by far the best MPG numbers. I never liked the other CCP configurations after trying them all, all had problems with smoothness over rev range or bad MPG returns.

For those who can't get their bike to idle in normal range:

With both air-screws fully closed I tuned TPS down to around 270 mV (which was 1000 rpms), synced r/h TB with throttle cable adjuster on the TB and then opened up air screws half a stop to make it idle at 1100 rpms and synced idle revs again with air-screws. This way I let idle revs not to fully depend on the butterflies openings (vs air screws fully closed with no air bypass option) and as a result the idle was now set within the normal range. Bike's smooth, surprisingly there's no surging considering it's below the recommended 370 mV and sparkplugs do not show too lean mixture after a bit of testriding it around. Probably the lambda sensor corrects the mixture as it's supposed to.

I reckon you can do the same the other way round if your bike revs too low - tune up the TPS voltage above 400 mV when you need to, to make it idle within normal range of 1000 - 1150 rpms as specced by the factory.

I do not get any TPS error code response from Montronic, thus planting the TPS to a flat 0.270 volts is fully acceptible for the Motronic brain. I reckon the same is true when going above 0.400 volts, looks like it's a fairly tolerant FI system over wider settings than what's written around the internet (not to go below 370 mV or above 400 mV).

I think riding with l/h TB stop screw loose maybe wore out the butterfly's corners enough to fully close it above the TPS adjustability range (below minimum TPS angle). At least that's my theory now. Hopefully it'll stay together for a short holiday trip and doesn't burn a hole into piston

 

[Roger 04 RT]

If that works for you I wouldn't argue with success. And the Motronic is forgiving in a lot if ways. If turning the TPS to 270 mV brought your idle down it did it by leaning the mixture.

I just spent a month off and on helping a guy with what turned out to be an idle issue. Check it out: http://bmwsporttouring.com/ubbthreads/ubbthreads.php?ubb=showflat&Number=895474#Post895474. The conclusion of this effort is that getting the TPS set well and the idle apeed correct pays dividends.

There is a better way than zero=zero to bring your idle down and a better way to set your TPS than voltage, I can write it down if you're interested.

 

[MattW]

There is a better way than zero=zero to bring your idle down and a better way to set your TPS than voltage, I can write it down if you're interested.

Roger,
I'd be interested to hear about your procedure of you have it documented anywhere.

 

[Roger 04 RT]

Matt,
I'm not a fan of adjusting the throttle stop screws or TPS, since they're factory calibrated. Many have already been altered using the zero=zero procedure (and there may be wear beyond adjustable BBS limits) creating a need restore either setting. What follows is a work in process.

There are three conditions that need to be satisfied at Idle speed for the Motronic, TPS and throttle to be aligned:

1. The TPS must be registered to the Motronic.
2. The engine must be warm and functioning in Closed Loop (or on the R1100 European version without catalytic converter, set idle CO to 1.5% using the CO Pot).
3. The Idle speed must be set to spec (e.g. 1100 RPM, +/- 50).​

I'm not going to provide all the details (e.g. explain how to work the throttle stop-nuts), just the essential steps for #1 and #3 above.

1. TPS

The best method for setting the TPS does not involve a voltmeter since the purpose is to align (register) the TPS to the Motronic; therefore you need an output from the Motronic to know you've got it right. The TPS voltage is an interesting byproduct of the correct procedure.

R1100
The diagnostic connector has a TPS calibration pin. You can read about it in a few places:
A) http://www.bmwmoa.org/forum/showthr...1150RT-surging&p=948289&viewfull=1#post948289
B) http://www.largiader.com/articles/motronic.html
C) http://www.k11og.org/forum/viewtopic.php?t=2110&postdays=0&postorder=asc&start=0

R1150
A GS-911 is needed to check that the TPS signal is within range but from measurements on my bike if the voltage at idle is 0.35 to 0.38, the Motronic can register it with the following procedure. The exact voltage does not matter.
A) Remove Fuse 5 (or disconnect battery ground) for 5 minutes, then replace fuse.
B) Key On
C) Fully rotate throttle twice
D) Key Off
​

3. Idle Speed
Refer to this thread for the reason why Idle Speed is important to the Motronic: (starting here, Idle Speed for Correct Mixture).

The procedure below is so that TPS and idle speed don't interact. You may need a fan for cooling. Also it is important to have clean TBs and cable slack during adjustment. Cable slack re-adjusted per book when finished.

A) Fully warm up the motorcycle and have a fan for cooling. Throttle bodies and BBS airways must be clean. Loosen left and right cable adjusters for 2 mm slack to insure throttles stay on stops.

B) Remove the TPS but leave it plugged in to the harness. Set it to the idle position using the Motronic procedure outlined above in #1 (Diag Connector for R1100; TPS learn before removal, then GS-911 set to 0.32 degrees for R1150). (You could measure with DVM to learn the approximate voltage before removal.) By doing this, no matter what you do with the throttle stops, the Motronic will see IDLE input from the TPS and interaction is eliminated.

C) Set the BBSs to 1.5 turns, whatever is considered the neutral position.

D) Perform a TB sync & Idle Speed adjustment using the throttle stops and get as close as you can to idle spec. Then use BBS for final fine tuning. It is imperative that the idle speed is exactly the book value (1100 +/- 50 rpm for the R1150). Because the TPS is removed, it did not vary while you adjusted idle.

E) Attach the TPS to the left TB and set per procedure outlined in point 2 above.

When completed you will have TPS registered, BBS at about 1.5 turns and the motor idling at 1100 RPMs.
RB

 

[monkeyboy]

Blimey. So you can't do it without a GS-911 eh. With respect, I think this is fine on a perfect newish bike without too much wear and tear but on something old, worn, used, abused and maladjusted after a multitude of new bits and fettling then IMO i find you have to play it by ear and adjust accordingly till you hit the spot. I really think there is no absolute guaranteed procedure to get this perfect. It's good to try all the tips but what works for one might not work for another. It's very very easy to upset the equilibrium in my experience and with all the variables it's not easy to get it right.

 

[MattW]

Thanks for the reply Roger - very interesting

 

[Tsiklonaut]

Cheers Roger, that's more precise method indeed if you measure the exact mixture in the process.

I do have the the LED tester for Motronic pin, the same I use obtaining the error codes with, but always thought it just does the usual: set between 0.370 minium and 0.4V maximum(?) So never bothered to try it. I reckon I should try this method.

 

[Roger 04 RT]

If you try it, let us know how it goes.

Apart from not registering the TB correctly, there is another problem with zero=zero. According to Bosch the zero degree voltage for the TPS is 250 mV, not zero volts. The Lentini procedure overlooked that. By starting at zero volts the throttle is opened too much and the BBS can't always compensate.
RB

 

[Roger 04 RT]

Blimey. So you can't do it without a GS-911 eh. With respect, I think this is fine on a perfect newish bike without too much wear and tear but on something old, worn, used, abused and maladjusted after a multitude of new bits and fettling then IMO i find you have to play it by ear and adjust accordingly till you hit the spot. I really think there is no absolute guaranteed procedure to get this perfect. It's good to try all the tips but what works for one might not work for another. It's very very easy to upset the equilibrium in my experience and with all the variables it's not easy to get it right.

I would agree with you that its easy to upset the adjustments and not easy to get them right. Personally I'm not in favor of adjusting the TPS or throttle stops but if someone has altered them, there may be a need to readjust them and get them right.

The R1100 doesn't need a GS-911 and there's a way to do the R1150 without one also. Here's the link: http://bmwsporttouring.com/ubbthreads/ubbthreads.php?ubb=showflat&Number=896486#Post896486