High Idle / Balance isues

[chris ponkster]

Hi everyone, I am experiencing isues being able to get the throttle bodies to balance and get the idle rpm down. I have read and followed the numerous how to ref balancing. All cables are slack at idle including the fast idle one. Currently to get the idle even close the TBs are wildly out of ballance with the right tb idle scew in all the way in and the rh one out about one and a half turns. The left tb seems to suck a lot more than the right. As the bike gets hot (5 or 6 bars at about 125c) the idle creeps up to about 1500 - The tbs ballance out ok at 3k using the cable adjustors but no matter what I do the idle is high and the idle adjuster have little to no effect. I have checked for air leaks everywhere around the injectors and intake manifolds and found nothing.

Taking the two lower plugs off makes the bike run slightly slower but it still runs - so I think it is running on both stick coils. I also swaped the stick coils from side to side and the issues is the same.

My bike is a 2003 1150gsa (non ABS) - after market y piece and remus can

The bike was recently aquired and had been unloved for some time, in the process of doing it up it has had the following replaced:
Fuel filter,pump,injectors and u-bend pipe
Hall effect sensor
Cata Dan throttle body shaft and bushes on both sides.
TPS set using GS-911
bike running in open loop with no lambda sensor according to GS-911

On an older bike my brain would be screaming "AIR LEAK" - but I cant find one in the very short intake path and I am wondering if it is some "Electrickery" -

I throw myself on the mercy of the Hive Mind - please be gentle

 

[Hay Ewe]

Have you taken the BBS - Big Brass Screws - out completly and cleaned them and the air passages that they open / close (meter the airflow)?
Dirt build up here could cause an un even ness.

 

[chris ponkster]

I have cleaned the screws and they were quite manky - also put some cleaner down the holes. With the bike running and the screws out they seem to be sucking well. I do wish I had blown them out when doing the TB butterfly shafts and bushes. I may end up taking the TBs off again and checking the pasages are clear.

Have you taken the BBS - Big Brass Screws - out completly and cleaned them and the air passages that they open / close (meter the airflow)?
Dirt build up here could cause an un even ness.

 

[oblertone]

Down by your Right knee. Old but gold, and always a favourite

 

[Hay Ewe]

Oh, and a little wipe of silicone grease or vaseline on the BBS o-rings will help too.

 

[chris ponkster]

View attachment 459426View attachment 459427
Down by your Right knee. Old but gold, and always a favourite

First thing I checked

 

[chris ponkster]

Oh, and a little wipe of silicone grease or vaseline on the BBS o-rings will help too.

greased and replaced all the o rings

 

[Paul Young]

I’d suspect an air leak on one side, or slightly different leaks on both sides. The throttle bodies have an o-ring between them and the inlet tubes which are quite thin/fragile and I know both of mine had broken a year or two ago. I had similar symptoms that balancing was tricky and wildly different between the two sides. Like some of us, they’re getting to an age where they are likely to fail

 

[chris ponkster]

I’d suspect an air leak on one side, or slightly different leaks on both sides. The throttle bodies have an o-ring between them and the inlet tubes which are quite thin/fragile and I know both of mine had broken a year or two ago. I had similar symptoms that balancing was tricky and wildly different between the two sides. Like some of us, they’re getting to an age where they are likely to fail

Thanks Paul - I changed the o rings when srvicing the tbs, that said I don't think and airleak on that side if the buterflys would have an effect - but I may be wrong!

 

[NeilDD]

What about the little rubber blanking nipples on the underside of the inlet stubs.
They rot and fall off

 

[chris ponkster]

What about the little rubber blanking nipples on the underside of the inlet stubs.
They rot and fall off

Brand new ones fitted recently - I do think its an air leak but I'm buggered if I can find it

 

[Ian J Hartley]

I’m guessing you’ve had the throttle bodies off.

Are you certain you don’t have a leaking inlet manifold. They get hard with age, might be worth taking the left one off and applying grease or sealant to the mating surfaces to see if things improve.

 

[chris ponkster]

I’m guessing you’ve had the throttle bodies off.

Are you certain you don’t have a leaking inlet manifold. They get hard with age, might be worth taking the left one off and applying grease or sealant to the mating surfaces to see if things improve.View attachment 459509

TBH it was doing it before I took them off, but I am going to take them off again to clean the idle circuit holes that the BBS works on - so when doing that I will give the inlet rubbers a be shmear with silicon grease and see!

 

[Steptoe]

Cata Dan throttle body shaft and bushes on both sides.

I expect the throttle stop screws have been fecked about with when replacing the throttle stop screws.
You know, the screws which are set at the factory and shouldn’t be touched.

 

[chris ponkster]

I expect the throttle stop screws have been fecked about with when replacing the throttle stop screws.
You know, the screws which are set at the factory and shouldn’t be touched.

I replaced the shafts and bushes - but it is likely that someone fecked around with the stop screw before I got the bike. When I put the buterflys back in they had the same amount of light around them as before when shut. Is there anything I can do if they have be messed with?

 

[Ian J Hartley]

This might be worth a try.

Post in thread 'TPS Alignment, Idle Speed Adjustment: Beyond Zero=Zero'
https://forums.bmwmoa.org/threads/t...djustment-beyond-zero-zero.73962/post-1091142

 

[Steptoe]

This might be worth a try.

Post in thread 'TPS Alignment, Idle Speed Adjustment: Beyond Zero=Zero'
https://forums.bmwmoa.org/threads/t...djustment-beyond-zero-zero.73962/post-1091142

That’s what I was hinting at

 

[Ian J Hartley]

Here are my thoughts…..on setting the throttle stop screws.

Everyone talks about setting the TPS value, but the bike will run and idle with the TPS disconnected, well mine does…. ( I guess The Motronic has fixed internal TPS value). So for me all the TPS does is act like an accelerator pump in a normal carburettor.

So for the purpose of setting the idle it must be possible to balance the throttle bodies by setting both Air bypass screws to the same position, then balance using the throttle stop screws. Once the throttle bodies are balanced and the idle is set correct, then reconnect the TPS and set the voltage at idle. Then carry out the rest of the higher RPM balance adjustment with the cable adjustment.

I’ve never tried it, because I haven’t rebuilt my throttle bodies yet, but I’ll give it a try when I do.

Anyone else got any thoughts on this….

Ian

 

[chris ponkster]

Here are my thoughts…..on setting the throttle stop screws.

Everyone talks about setting the TPS value, but the bike will run and idle with the TPS disconnected, well mine does…. ( I guess The Motronic has fixed internal TPS value). So for me all the TPS does is act like an accelerator pump in a normal carburettor.

So for the purpose of setting the idle it must be possible to balance the throttle bodies by setting both Air bypass screws to the same position, then balance using the throttle stop screws. Once the throttle bodies are balanced and the idle is set correct, then reconnect the TPS and set the voltage at idle. Then carry out the rest of the higher RPM balance adjustment with the cable adjustment.

I’ve never tried it, because I haven’t rebuilt my throttle bodies yet, but I’ll give it a try when I do.

Anyone else got any thoughts on this….

Ian

Im going to have a go doing it this way - I have the TBS off to give another clean out and have taken the measurements of what they are now, so if it makes it worse I can put it bact to what it was. It does look like the LH one has been tampered with. With them both set at 1.3mm gap I will try to set the idle and balance with the BBS. If that doesn work I will try the other way using the stops top set the idle

 

[chris ponkster]

Well I seem to have got it done - it didn't want to play and I probably have broken all the BMW rules in the process. I did try doing the gap set at 1.3mm method but still couldnt get it to idle low enough, so I have set the idle and balanced using the stops and fine tuned with the BBS - I can hear everyone screaming "DON'T TOUCH THE STOPS" but tbh I didnt have much choice as the BBS alone were not adjusting the difference between the left and right TBs enough. Im not sure what was going on and I have gone a bit more grey in the process but I now have a bike that idles evenly at 1150ish and is balanced through the rev range.
Thanks for everyone assistance