Idle rise and fall

[Johny w]

I am experiencing an idle problem, when stationary, my tickover increases to around 1400rpm, then drops to around 1000, almost to the point of stalling. It does this with a normal running temperature, and it's a consistent timing 3 to 4 seconds on 1400 3 to 4 seconds on 1000, like clockwork. I've replaced all plugs, air filter, coil packs, gapped the tappets, replaced fuel filter, balanced and cleaned throttle body's, use the best fuel.....I've done all I can think of but it persists...... It runs great, with no misses and good acceleration.
Could it be the fuel pump on its way out?......would a failing hall sensor give these symptoms? It's done 44000 miles...... I would appreciate some thoughts on this, slightly annoying/concerning problem.

 

[JJH]

I presume it’s a boxer? How about running it on 1 side then the other to see if there’s something common or only on one side. JJH

 

[Johny w]

Yes, sorry, its a R1150gs 2003,
I read it was unsafe to remove one coil pack while it was running. But yes, that's a thought, simple, inexpensive things first.
Maybe a dicky plug or coil pack? It's very strange, as it's like I say, like clockwork.
I replaced both coil packs last year. Replaced battery last year too.....battery's charging ok.

 

[DrFarkoff]

I am correct in thinking this only happens when hot ??

Just disconnect the lamda probe, its the round plug that is cable tied to the front right steel diagonal frame rail where the ignition coil is.
Disconnecting it defaults the ECU to the default map (open loop Lamda has no input) its what you get before the lamda kicks in and not a problem to run it like that

Or maybe the Throttle position sensor has an issue with a shorting track but the regularity of it suggests Lamda

BUT without Data it would only be a guess

 

[Steptoe]

Pull both lower secondary plug caps off so it’s running on just the main coils .. see if it starts and runs on both cylinders .

Also check you have slack in the throttle cables so it’s actually running on the throttle body idle tubes and not the cable tension

 

[Johny w]

I am correct in thinking this only happens when hot ??

Just disconnect the lamda probe, its the round plug that is cable tied to the front right steel diagonal frame rail where the ignition coil is.
Disconnecting it defaults the ECU to the default map (open loop Lamda has no input) its what you get before the lamda kicks in and not a problem to run it like that

Or maybe the Throttle position sensor has an issue with a shorting track but the regularity of it suggests Lamda

BUT without Data it would only be a guess

Yes only when hot, I'm out on it today and it's cut out twice when coming to a stop

 

[DrFarkoff]

Yes only when hot, I'm out on it today and it's cut out twice when coming to a stop

Undo the tank bolt, CAREFULLY slip the tank back you can do this without disconnecting your fuel lines but be caareful as at this age they are brittle!!!!!

Male connections should really be changed they are the ones that usually snap off!!!

But slip tank back and tilt up (get someone to hold it) and locate the Lamda / O2 sensor and unclip the connection and tuck it safely away and then see what happens once up and running again

Tickover is 1050 + or - 50 rpm So you may need to screw the Big Brass Screws in or out in equal increments (each side) of about an 1/8 th turn to get you in the ball park at 4 bars on your temp gauge Try not to run over 1150rpm or it will get damn hot in standing traffic

N.B. Never touch the slotted 7mm throttle screws on the inside of the throttle body

 

[Johny w]

Thanks very much, I'll try that

 

[Johny w]

With hot engine, I took off both secondary plug caps, bike started ok and ran a bit slower 1000rpm, but when I revved it, there was an initial knock, like pre ignition, apart from that it it ran OK. The slight knock was only the first rev, low down.
Plug leads back on, and the tickover speed increased to about 1200 but fluctuating slightly......
Does this make sense? And would it be normal for the idle speed to decrease slightly?
Still felt smooth, like both coils are OK.

 

[Johny w]

Undo the tank bolt, CAREFULLY slip the tank back you can do this without disconnecting your fuel lines but be caareful as at this age they are brittle!!!!!

Male connections should really be changed they are the ones that usually snap off!!!

But slip tank back and tilt up (get someone to hold it) and locate the Lamda / O2 sensor and unclip the connection and tuck it safely away and then see what happens once up and running again

Tickover is 1050 + or - 50 rpm So you may need to screw the Big Brass Screws in or out in equal increments (each side) of about an 1/8 th turn to get you in the ball park at 4 bars on your temp gauge Try not to run over 1150rpm or it will get damn hot in standing traffic

N.B. Never touch the slotted 7mm throttle screws on the inside of the throttle body

I'm going to try this when I have more time and less fuel in the tank.
My tank connectors are fine, had them off a while ago and silicone greased the o ring. Can you use an aftermarket O2 sensor, or is the connection critical?
May as well replace it!!

 

[Johny w]

Undo the tank bolt, CAREFULLY slip the tank back you can do this without disconnecting your fuel lines but be caareful as at this age they are brittle!!!!!

Male connections should really be changed they are the ones that usually snap off!!!

But slip tank back and tilt up (get someone to hold it) and locate the Lamda / O2 sensor and unclip the connection and tuck it safely away and then see what happens once up and running again

Tickover is 1050 + or - 50 rpm So you may need to screw the Big Brass Screws in or out in equal increments (each side) of about an 1/8 th turn to get you in the ball park at 4 bars on your temp gauge Try not to run over 1150rpm or it will get damn hot in standing traffic

N.B. Never touch the slotted 7mm throttle screws on the inside of the throttle body

Ok I've got a new 02 sensor to put on, but I'm unsure if I need to take the front portion of exhaust to heads off. I which case I'll need new exhaust gaskets I presume.
It looks as though I can remove the rear muffler from the middle section, and then the two exhaust clamps and two allen bolts.
And maybe tie a thread onto the old sensor wiring when removing the centre section so I can follow the route with new sensor wires.
But is it difficult to remove the centre section away from the two front pipes without disconnecting the two pipes at the head.
I hope you can understand what I'm saying. Thanks in anticipation Johnny

 

[DrFarkoff]

Overcomplicating it @Johny w

Number 1 Did you run it with the Lamda disconnected ??? This will prove it is the Lamda that is source of the problem ??

Anyway ...Undo Bolt to frame on silencer undo the clamp that is also the Chrome shroud at the front of it adn slide silencer backwards but keep shroud on cat side of things

Undo clamps x 2 on the Headers to Cat

(There may be 2 x countersunk allen screws towards the centre of the bike but depending on year if they were fitted or not! Age dependent thing)

Fit the Lamda into the Cat

Fit the cat to the bike with the Lamda cable out to the right side of the bike

Fit rear can

Align everything

Tighten all clamps and mount screws

Follow routing of the old lamda cable and connect it at the tubular frame rail

 

[Johny w]

Overcomplicating it @Johny w

Number 1 Did you run it with the Lamda disconnected ??? This will prove it is the Lamda that is source of the problem ??

Anyway ...Undo Bolt to frame on silencer undo the clamp that is also the Chrome shroud at the front of it adn slide silencer backwards but keep shroud on cat side of things

Undo clamps x 2 on the Headers to Cat

(There may be 2 x countersunk allen screws towards the centre of the bike but depending on year if they were fitted or not! Age dependent thing)

Fit the Lamda into the Cat

Fit the cat to the bike with the Lamda cable out to the right side of the bike

Fit rear can

Align everything

Tighten all clamps and mount screws

Follow routing of the old lamda cable and connect it at the tubular frame rail

 

[Johny w]

Thanks very much for that, I didn't run it with it disconnected, ....I've been away for a month so thought I would just do it anyway.
It seems pretty likely to be that, but it will eliminate it if not.
I'll let you know how I get on, thanks again

 

[Johny w]

Done the 02 sensor today......good result, it took quite a bit effort to get the rear can off, but managed eventually.......running great now, thanks for the advice.

 

[Johny w]

Overcomplicating it @Johny w

Number 1 Did you run it with the Lamda disconnected ??? This will prove it is the Lamda that is source of the problem ??

Anyway ...Undo Bolt to frame on silencer undo the clamp that is also the Chrome shroud at the front of it adn slide silencer backwards but keep shroud on cat side of things

Undo clamps x 2 on the Headers to Cat

(There may be 2 x countersunk allen screws towards the centre of the bike but depending on year if they were fitted or not! Age dependent thing)

Fit the Lamda into the Cat

Fit the cat to the bike with the Lamda cable out to the right side of the bike

Fit rear can

Align everything

Tighten all clamps and mount screws

Follow routing of the old lamda cable and connect it at the tubular frame rail

Thought it was solved, but I was mistaken, once I'd been on a good run the problem was still there.
Doesn't seem as bad, but it's still a niggle I'd like to solve. I was thinking it. May be the air sensor above the air filter......any pointers would be appreciated.

 

[theoneandonly]

have you plugged any diagnostics into the bike ?

 

[Johny w]

have you plugged any diagnostics into the bike ?

No, I don't possess one, and the dealer charges are extortionate.

 

[theoneandonly]

No, I don't possess one, and the dealer charges are extortionate.

try a normal bike shop , or find an indy. there must be an indy not too far away ?
a shop should have a diag kit , you might have to pay for a lead ( which will be yours )

 

[Johny w]

try a normal bike shop , or find an indy. there must be an indy not too far away ?
a shop should have a diag kit , you might have to pay for a lead ( which will be yours )

Thanks, I do know a non BMW shop, I could ask the question.
A gs911 would be handy, but it's a lot to fork out for a once in a blue moon use.
I've exhausted my easy fixes apart from the air sensor, before spending say £40 for a shop to do a two minute test, do you not think that money would be better spent on a gamble on a sensor?