R1100GS Misfire - Help Needed Please

[JoePap]

Any ideas from forum members would be much appreciated. I'm not a mechanic but I've always maintained my own motorbikes.

I've owned my R1100GS since Jan 2012 and it's been reliable. It's standard with no catalytic converter and no lambda sensor. There's never been any coding plug in the fuse box. It's done about 40,000 miles. It was imported from Germany in 2002 by the previous owner. I've owned it for three years with no engine problems and done a few thousand miles (I've other bikes).

It developed a misfire and I've had no luck fixing it. The misfire is only apparent under load, i.e. accelerating through the gears second and onwards. It comes on when the throttle is opened wide. On slight throttle in first gear the bike will rev to the red line. It's not quite so bad when the bike is cold but gets very bad when the bike is warm. The bike is always stored in the garage and the problems occurred at the start of this summer when everything was nice and dry and warm.

The air-bleed caps are in place on both throttle bodies.
The valve clearances were checked recently and only slight adjustment was needed.
I balanced the throttle bodies recently. The bike seemed OK before and ran well afterwards. Not really sure if it improved.
I've drained and examined the fuel, finding no water or contamination.
The fuel pump can be used to pump out the tank with no sign of any flow restriction as the tank empties
I've changed to fresh fuel
The air-filter is new and the air-box is clean. If I disconnect the airbox pipes and run with open carbs the fault is still the same.
The throttle cable works smoothly and both throttles open progressively and seem mechanically fine
The choke cable seems to work fine - nothing's sticking
Replaced the spark plugs
Replaced the coil and leads
Replaced the hall sensors
Made up a mini wiring loom that runs the ignition and fuel system independent of the main loom. The bike runs the same on that, or on the original loom.
The mini loom has a different CO potentiometer
The fuel pump runs well and circulates the fuel quickly
Fuel is being delivered rapidly to both fuel injectors (Can only test this on the ramp though)
My Throttle Position Sender seems to work OK. I've wired a voltmeter to both tracks and see the volts rising as I turn the throttle up to approx 4v on the quarter turn and on the other track on the full turn.
I've tried another ECU and again the fault is the same.
along the way I have experienced the following three motronic fault codes but after changing things around they are now all cleared and I'm getting 4444 = No faults

1111- CO2 Potentiometer
1215 - Throttle Position Sender
- Hall Sensor 2 (Can't remember what that code was)

So now the tester reads 4444 - No faults - but the misfire remains none-the-less
I've got some more ideas to try

Compression test
Rechecking the valve clearances
Rechecking the throttle balance
Having the injectors cleaned and serviced

But it feels like I should have solved it by now so I'd appreciate any ideas anyone can give me.

Sorry this is such a long and detailed first posting.

Thanks.

Joe

 

[MikeO]

When you checked the injectors, did they both spray a similar fan shaped pattern?*A blocked or worn injector could possibly cause those symptoms...

 

[cele0001]

From the description, you have fuel starvation issue. If it only happens under load it should be fuel. Is it pop, pop misfire or more bogging down lack of acceleration?. Make sure fuel pressure and delivery volume are OK.

 

[JoePap]

Yes, the fuel injectors both seem to deliver a similar fan shaped pattern and delivery increases nicely as the bike is revved.
When the throttles opened wide in gears above 1st the bike seems to bog down and there are sometimes pops.
There is a strong flow of fuel at each pipe to the injectors and each injector seems to fire and deliver OK.
Thanks for the suggestions.

 

[GORILA]

Can't harm to have your injectors reconditioned. I had what seemed like fuel starvation problems on my 98 R1100GS. In the end a refurb sorted out my problems
I used the following link http://mrinjectoruk.co.uk/BMW-motor-cycle-fuel-injector-service-P2620607.aspx, which may be of use to you!

regards.

 

[Pekkavee]

What is your TPS reading in Volts? In standstill, no throttle.

Pekka

 

[JoePap]

The readings from the TPS with the throttle closed are
- Track 1 (The track that does the first quarter throttle) 0.39
- Track 2 (The track that covers the full throttle range) 0.02
The readings from both tracks look normal as the throttle is opened. Rising to over 4v.

I tried riding the bike with first the left hand injector lead unplugged and then with the right hand unplugged.
Either way it seemed the fault was present with similar very poor power at full throttle. But did seem that the right injector performed worse, with occasional spits back through the throttle body.

Even with both injectors firing the performance is awful. Even in second gear the bike won't rev with the throttle wide open. It bogs appallingly.

It was absolutely fine before the fault developed.

Maybe an injector overhaul is the way forward but I'm also wondering about the TPS and throttle body sync. Could the position of the TPS and or throttle sync cause such a serious power loss and misfire?

I'm not really very familiar with how to set up the throttle bodies properly. They've never needed attention before. I balanced them once -following instructions and the result seemed fine. I've left them alone since.

Thanks.

 

[Smug]

Have you done a compression test?

 

[JoePap]

Compression test : I've got 165 psi on both cylinders.

 

[Roger 04 RT]

Although you've made a lot of checks on your fuel system, I agree withe cele0001. Here is a better way to test fuel capacity: measure the volume of fuel returning TO the tank at idle. That means measuring the flow of the top plastic tube coming FROM the fuel distributor.

On the R1150 it's easier because there is a QD, quick disconnect. On the R1100 you need to interrupt the hose going back to the tank (top hose) and measure the flow coming out of the top tube of the fuel distributor. It should be two liters per minute at idle. If you get that it means that you pump operates at full capacity, the filter isn't clogged and the in-tank hoses don't leak.

The tests you made so far only show that there is some fuel under pressure, not that there is enough volume at full pressure.

 

[JoePap]

Hi Roger

Yesterday I checked the valve clearances and they are fine. No signs of any problems, valves operate as they should. As mentioned in the previous post, the compression is good on both cylinders.

I've got a simple switch to power the fuel tank. I've been using it to drain the tank which has been on and off many times now. Certainly the flow seems fairly fast but I agree I should check it. Thanks for confirming the flow-rate should be two litres per minute. I'll test and report back.

So with my manual over-ride switch I can test the flow rate without the bike running but do you think I should also test the flow from a T-piece with the bike running?

Thanks Roger.

 

[JoePap]

I've checked the fuel deliver taking off and measuring the fuel from the return union. I get two litres after one minute. So that too seems fine.

Sending away the injectors for checking seems the next step however, the bike is booked in to SBW Motorrad in Welwyn Garden City Saturday 29th so I'll get SBW to check the injectors.

In the meantime, any other suggestions would be appreciated.

Thanks.

 

[Timolgra]

Your pump is delivering plenty of fuel at idle and the test suggests it would also at full throttle.

So why not?

I'd be replacing the filter as well as all the fuel lines and clamps in case they've broken down internally causing a partial blockage or leak at high fuel volume.

 

[Roger 04 RT]

I've checked the fuel deliver taking off and measuring the fuel from the return union. I get two litres after one minute. So that too seems fine.

Sending away the injectors for checking seems the next step however, the bike is booked in to SBW Motorrad in Welwyn Garden City Saturday 29th so I'll get SBW to check the injectors.

In the meantime, any other suggestions would be appreciated.

Thanks.

If you get two liters per minute at idle then your pump, filter and hoses can supply approximately 3X the quantity of fuel required at full power. I'd say you're good to go on the in-tank fundamentals.

The R1100 and R1150 circulates full fuel flow even at idle. It just returns less to the tank if more is used by the injectors. A 90 HP engine uses about 45 lbs of fuel per hour at full power. That's roughly 8 gallons per hour. Your pump is outputting 30 gallons per hour so you're right in spec.

 

[Smug]

Have you checked fuel pressure at the injectors?

 

[JoePap]

Sorry, I don't yet have a fuel-pressure tester. They're cheap enough on ebay but the bike's booked to go to SBW Motorrad on Saturday. If I buy a tester it won't arrive before then.
The fuel flow is good at two litres per minute so it seems likely the pressure is OK.
Any other suggestions would be appreciated in the next day or two. I'd like to find the fault myself but the most likely seems to be the injectors giving a weak spray on full throttle. I don't have any way to test the injectors either before it goes to SBW so unless there's anything else to try, it's going to be over to them.
Thanks for the suggestions so far.
Joe

 

[GORILA]

Why don't you try refurbishing your fuel injectors. For £25 you may solve your problem, certainly cheaper than the dealer will.

 

[Nick591]

Some suggestions/thoughts. Might be an ignition timing issue caused by confused ECU. How does the ECU detect engine rpm? Could there be a fault with that sensor? AFAIK your bike should have a beige cat code plug too (I have a 1999 1100GS with no lambda or cat and it has a beige plug). What year is yours? Have you checked your TPS setting to be 0.377V with throttle closed? Have you checked the CO pot setting? If something is confusing the ECU with an unexpected input it might cause these symptoms. Many threads on here from experts like Roger04RT about checking TPS and CO settings.

Sent from my GT-I9505 using Tapatalk

 

[Roger 04 RT]

Sorry, I don't yet have a fuel-pressure tester. They're cheap enough on ebay but the bike's booked to go to SBW Motorrad on Saturday. If I buy a tester it won't arrive before then.
The fuel flow is good at two litres per minute so it seems likely the pressure is OK.
Any other suggestions would be appreciated in the next day or two. I'd like to find the fault myself but the most likely seems to be the injectors giving a weak spray on full throttle. I don't have any way to test the injectors either before it goes to SBW so unless there's anything else to try, it's going to be over to them.
Thanks for the suggestions so far.
Joe

Joe, You've done a great job checking the basics. Compression, spark, fuel flow, spray pattern all seem good.

Unlike the R1150 where a GS-911 can read the sensors, on the R1100 you're flying blind on what the sensors are doing. To calculate how long to open the injectors the Motronic takes RPM dats from the HES and throttle data from the TPS to determine the "engine load". Using those two sensors, the Motronic uses a look up table and finds injector on time. That injection time is then slightly modified for air temperature and barometric pressure. Of all four sensors, the TPS signal most influences injection pulse length because throttle angle is the closest measure of engine load.

This is just a guess, but it may be that your TPS isn't sending a good signal to the Motronic, or your HES is acting up. Can you borrow a known good TPS? If you can, set the voltage between pins 1&4 to 340 mV (not critical for high power tests) and see if the TPS replacement improves things. If not, you probably should inspect or replace the HES.

I'm not positive but I believe that your injectors put out about 300 cubic centimeters of fuel per minute. You could power up the fuel pump by jumpering the fuel relay and then energize the injector and see you much fuel you collect in a minute.

 

[DrAlf]

Joe, You've done a great job checking the basics. Compression, spark, fuel flow, spray pattern all seem good.

Unlike the R1150 where a GS-911 can read the sensors, on the R1100 you're flying blind on what the sensors are doing. To calculate how long to open the injectors the Motronic takes RPM dats from the HES and throttle data from the TPS to determine the "engine load". Using those two sensors, the Motronic uses a look up table and finds injector on time. That injection time is then slightly modified for air temperature and barometric pressure. Of all four sensors, the TPS signal most influences injection pulse length because throttle angle is the closest measure of engine load.

This is just a guess, but it may be that your TPS isn't sending a good signal to the Motronic, or your HES is acting up. Can you borrow a known good TPS? If you can, set the voltage between pins 1&4 to 340 mV (not critical for high power tests) and see if the TPS replacement improves things. If not, you probably should inspect or replace the HES.

I'm not positive but I believe that your injectors put out about 300 cubic centimeters of fuel per minute. You could power up the fuel pump by jumpering the fuel relay and then energize the injector and see you much fuel you collect in a minute.

What an incredibly detailed and interesting response I didn't know that the R1100 wasn't compatible with a GS-911. I'm guessing that means that the dealer will also have limited visibility of the fault when the bike is taken there on Saturday right?!

Please do keep this thread updated with findings - it sounds like a particularly difficult problem to sort. Good luck