Tickover racing when hot......................................

[52blackshadow]

Evening All,
my 04 reg 1200GS has a problem. When it gets warn, the tickover becomes really fast. If I stop the engine, turn the ignition back on, twist the throttle a couple of times then restart it settles down to an even tickover again, but once ridden away it soon goes back to a really high tickover.

I suspect it's a sensor of some sort, perhaps the Lambda sensor in the exhaust, but don't want to start buying bits at random until I find what is causing the problem. Anyone had this happen before? Or anyone know what the problem is likely to be?

Appreciate any help,

Keith.

 

[Bendy toy]

Do a TPS reset.
Check connectors to throttle stepper motors.

 

[Spout]

Could be one of the plastic covers on the throttle cams is dislodged. Holds open the throttle slightly.

 

[52blackshadow]

Thanks Chaps............................................

Thanks for the input Chaps. I don't think it's the cable or plastic cover, because if I stop and then do a TPS reset it settles down to a steady normal tickover, the increases with riding. I did open the connections to the stepper motors and clean them, but it doesn't seem to have made any difference. I disconnected the Lambda sensors this morning, and the Tickover so far has stayed slow and steady, so I suspect this might be the problem.

Anyone able to advise on a. testing the Lambda sensors, and b. the impact of leaving them disconnected?

Ride safe,

Keith.

 

[Bendy toy]

My lambdas got sooted up badly when primary coils were failing otherwise have been 10% solid.
You could also check connector to air inlet temperature sensor.
If that is flicking about fuel mixture will vary.
Dodgy crank position sensor can do strange things when hot. But very hard to test.
You probably need a GS-911 to find the culprit.

 

[DrFarkoff]

Slacken cables off so that the throttles are properly closed (i.e. a mm or so of slack in cables) at tickover then the Steppers adjust the rate of bled in air to control the tickover

It takes very little air to make them rev up

 

[Deleted account 190920001]

I can't see it being the O2 sensors. They affect how much fuel goes in, not how much air. They also do nothing at idle.

Grab a can of wd40 and spray round the joint of TB to cylinder head. If the revs rise you have a vacuum / air leak which would very definitely give you erratic and high idle. Grab the TB and give it a good push pull while your doing it.

Other solution would be the throttle hanging up or a sticky idle stepper valve.

I am going for the air leak though.

 

[Bendy toy]

Has the bike been serviced recently?

 

[52blackshadow]

Servicing...................................

Hi, I service the bike myself, and last did so about 1500 miles / 6 months ago. Disconnecting the Lambda sensors has cleared the problem up for almost 100 miles, so suspect this is the cause. So back to the earlier questions, can each one be tested - if so, how? and what is the impact of just leaving them disconnected?

Appreciate any feedback, the bike is approaching 110000 miles, so I don't really want to spend much on it.

Cheers,
Keith.

 

[Bendy toy]

The sensors measure oxygen content in the exhaust gas (as we know). Too much unburnt fuel from say a faulty spark plug will leave some O2 unused so the sensors can make the engine run rich and really soot up the plugs aggravating the problem.

If there is an air leak after the throttle valve there will be too much O2 so the sensors cause the ECU to add more fuel to correct the picture. Engine then runs fast on tickover because the ECU simply matches fuel fuel and air flows.

In either case, disconnecting the sensors "solves" the problem but has only removed the symptom because the mixture measurement system is now not working as it should.

@Marki-GSA's suggestion sounds likely. Try the air leak test with Easy Start or WD-40. Best done with the sensors unplugged as they will otherwise correct the lean mixture and cause the engine to rev.

 

[52blackshadow]

Thanks Bendy Toy, that makes a lot of sense! Will check later.

Cheers,
Keith.

 

[52blackshadow]

Update.............................

Well, I left the Lambda sensors disconnected, and after a couple of days, the idle speed has started to rise again, not as sharply as it did previously, and it does tend to come down again slowly if the throttle is blipped! I tried spraying WD40 all around the throttle bodies and connections with the bike ticking over, and it didn't make any difference, so suspect it isn't an air leak. Will try disconnecting the temperature sensor for my run home, and see if that changes anything!

This is why I hate my 1200GS sometimes!

Ride safe,

Keith.

 

[Spout]

When tickover is racing, try closing the throttle cams fully (fingers behind the bodies).

 

[Deleted account 190920001]

I think its time you got hold of a GS911. Tracking this down could take a long time otherwise on something fairly complicated like a hexhead.

 

[DrFarkoff]

I tried spraying WD40 all around the throttle bodies and connections with the bike ticking over, and it didn't make any difference, so suspect it isn't an air leak. Will try disconnecting the temperature sensor for my run home, and see if that changes anything!

You may as well have pished on it! than spray that schite near all the rubber bits Keith

Did you check you definitely have free play on the throttle cables at LEAST 1mm

It takes a Gnats Gnadger of throttle opening to make them rev up 2 ~500 rpm

 

[Mistacat]

+1 for the GS911.
There are so many things that it could be , plug a GS911 in and study the real time data, you will also be able to look at the output wave forms from the lambda sensors to check them. ( it wont use one of the vin slots on the GS911).
Must be someone in your area with one. I would be happy to plug it in for you if you were in this area.

 

[Bendy toy]

It's counter intuitive but engines running weak will tick over fast. 2 strokes are especially prone to it but 4 strokes also do it. This suggests there is an air leak between throttle valve and cylinder head.

 

[Spout]

This suggests there is an air leak between throttle valve and cylinder head.

Or the throttle valve not closing properly. Caused by "malfunction" of:

Twistgrip
Throttle Cables
Cable Junction Box
Throttle Cams
Throttle Valve Spindle
Crud

 

[DrFarkoff]

Spout ,

You can lead a horse to water and all that ......

I have been saying like but they must think I am some looney looking to make a flux capacitor

Or the throttle valve not closing properly. Caused by "malfunction" of:

Twistgrip
Throttle Cables
Cable Junction Box
Throttle Cams
Throttle Valve Spindle
Crud

 

[Bendy toy]

Or the throttle valve not closing properly. Caused by "malfunction" of:

Twistgrip
Throttle Cables
Cable Junction Box
Throttle Cams
Throttle Valve Spindle
Crud

Yes but the OP's bike only revs when hot.