My GS is really thirsty!

Tonguska

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Hello everyone!

Quick question. What is your average motorway MPG? My 2011GS has suddenly developed a massive thirst for petrol. It says on average 35miles per gallon and range of 120miles on a full tank. That isn't normal, right?
I am using it only to get to work and back which is 95% motorway where I am sitting at 70mph and 4.5-5k revs all the time. What could be the cause of this?
 
All 3 Hexhead GSA's I have owned returned mid 50's mpg on the motorway, with 55-60 average pootling around. Lowest ever on motorway 46mpg loaded, two up and shall we say making progress.
 
My 09 GS averages 49.8 get used enthusiastically.
But I guess you’d rather have possible causes proffered...
Check plug colour, air filter and particularly binding brakes if first too seem ok.
 
Fuel consumption

"sitting at 70mph and 4.5-5k revs all the time"

Your revs sound high at 70mph?
 
Fuel consumption on mine dropped like yours one time. After much prodding and probing with a gs911 it was the throttle position sensor. Replaced it and back to normal service.
 
All 3 Hexhead GSA's I have owned returned mid 50's mpg on the motorway, with 55-60 average pootling around. Lowest ever on motorway 46mpg loaded, two up and shall we say making progress.

Yep, wot he said.....
 
Fuel consumption on mine dropped like yours one time. After much prodding and probing with a gs911 it was the throttle position sensor. Replaced it and back to normal service.

That would actually make a lot of sense. I had a problem with my throttle after changing the battery few months ago and that's when it all started going downhill for my bike. What would be the best method of checking if it is actually a throttle position sensor?
 
Did you do a TPS reset after connecting the new battery?

Al.

Edit, beat me to it mucky helmet.
 
Yes I did! 😀😀 Is it possible that TPS did register it? Or actually what is more likely is that I messed it up.... Should like me actually 😑
 
Reset not necessary it learns itself as you ride it

1200 Hex head TPS are not adjustable Just buy a new one

I "think" I saw on here someone had found an after market TPS from an early 3 series that fitted

Edit I really should slap myself :rob Diagnosis is required! rather than just swapping bits Unless you have a chum with a 1200 that will let you

As an Explanation the TPS basically tells the ECU the angle of the Throttle valve

So when the throttle is closed the ecu only injects enough fuel for tickover If yours is faulty and showing 25% throttle it will inject fuel for that throttle opening

If you notice your exhaust putting out soot when at tickover this is a good indicator

TPS sets fuelling but you need a known good one or a GS911 or similar to check

Lamda corrects fuelling and same as above but there are two of them Definitely a GS911 or other diagnostic needed

Main Plug stick coils are prone to failing so that could also be an issue as the bike will not be running efficiently! Do you notice a misfire under load? Is the tickover rougher than normal ??
 
The aftermarket ones were about £25. Ebay. Two screws and an electrical connector is all. Plug and play from memory (you might need to do an adaptations reset actually do a GS911 may be needed.

If you want to check first though you need a GS911. Go on real time data or whatever it’s called. Select the TPS and max sampling rate. Watch the read out on the graph and you should see nice smooth progression (actually it’s very small steps as the throttle opens in tiny steps) as you open and close the throttle. Anything else is not right. I started a thread I think on my problems. It’ll be about 2017 or 2018.
 
How come when I changed my battery and was ignorant of the TPS reset, my bike is all OK?
 
How come when I changed my battery and was ignorant of the TPS reset, my bike is all OK?
Coz you don’t need to do a tps reset when you change the battery. At least I never did. I will have disconnected my battery dozens of times.

Tbh I am not actually sure what a tps reset is or how it works. There’s an adaptations reset needed just about anytime you fiddle with the throttle settings. But a tps reset???
 
The TPS ( Throttle position sensor) reset is not required on R1200GS bikes only the 1150 bikes with adjustable TPS the R1200 TPS is not adjustable.
If the battery is disconnected for a few minutes the adaptations made to the long term fuel trims are lost, It will re build these adaptations over a few tanks of petrol.
There may also be changes to the Ignition map etc ? I have no way of measuring those.
I have fitted the aftermarket (Hella) TPS sensors from ebay and would consider them a service item every 50K miles.
 
In addition to the potential TPS issue, there is one more part that may cause a problem. A failed O2 sensor/sensors may also contribute to increased fuel consumption, as the fueling is based on feedback from the O2 sensor and adjusted accordingly. So... a faulty feedback may mean an incorrect (as in higher) fuel flow.

Before running of replacing components i humbly suggest that the bike is properly diagnosed and analyzed.

Proper TPS function my be checked by comparing the vacuum after the throttle valve on both sides. The TPS value may be read as a voltage, but a faulty feedback may be a potential issue.
If both sides operates with similar vacuum, the TPS is probably working as it should, and next focus should be on the O2 sensors.

A too rich mixture would be reflected by the color of the sparkplug.
Also, resetting the long term fuel trim and checking the lambda correction value in real time may give a clue to a faulty sensor.

Allow me to elaborate this point:
With a stock mufler and fresh air filter, the standard OEM mapping in the bike should be fairly close to what the engine needs for proper fueling. Thus, on a new engine, it should be running well even before the adaptive table (long term trim on the non BMW world)is built. Actually, you may even experience that the OEM mapping calls for a slightly too rich fueling in order to make sure the engine does not run too lean. Hence, with a reset adaptive table, the lambda correction with a healthy O2 sensor should be next to nothing, with a possibility for a negative adjustment.
On the other hand, if the O2 sensor reports a too lean feedback when the actual fueling is normal, the ECU will command an adjustment command to increase the fueling in order to reach the proper mixture, based on the feedback from O2 sensor.
 


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