Misfire & data logs

Santa-2512

Santa-2512

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Did a couple of runs out yesterday with the GS911 connected as a data logger

The misfire once warm is still there.. :(

Still under the diagnosis stage at the moment... not sure if its plugs, coil, or fuel at this stage.

ive downloaded the relevant engine data log for the run.

what values would show the misfire ??

next step would be to get it hot and disconnect coils to see if that shows which coil ( i dont fancy replacing all four

at once lol )
 
Not sure that it will actually show this directly, the only real test being the resistance test on the coil itself, and only then when its in its "breakdown" phase. Do you have a mate with matching bike that would lend you a coil? Usually the secondaries break down first - because they are more exposed?
I think what you might be looking for is a "dyno" type graph which would allow you to visualise the problem? Don`t think this is available.
 
Last edited:
My primary coils smelled of hot insulation. Just removing the plastic covers you could not miss it. The new coils have no smell at all. I have run the bike with and without secondary coils it does not cause a missfire and the O2 sensors remain a good colour.


Sent from my iPhone using Tapatalk Pro
 
Oh dear thats exhausted my contribution!
Lets hope someone comes along shortly with a better offering.
 
Follow the trace of the O2 sensors. If it is a miss fire should spike rich, if its fuel it should spike weak. The O2 sensor will show the side its all happening at. Its possible if it is just missing once every so often it won't show anything but if you are feeling it then it should show as it is a longer event

Random misfires are rarely fuel and more likely coil or possibly plug.
 
Misfire & data logs

My last bike (air cooled) with two wasted spark coils and ht leads would kill a set of plugs in 10,000 miles. Twin electrode plugs might have lasted longer but after a year the exposed plugs were tight indeed. I check the BMW plugs at same mileage partly habit but I don’t want the secondaries to get stuck solid.
The issue could easily be plugs. You can get the NGKs in same heat range in single electrode type for not much money.
 
Bendy toy said:
My last bike (air cooled) with two wasted spark coils and ht leads would kill a set of plugs in 10,000 miles. Twin electrode plugs might have lasted longer but after a year the exposed plugs were tight indeed. I check the BMW plugs at same mileage partly habit but I don’t want the secondaries to get stuck solid.
The issue could easily be plugs. You can get the NGKs in same heat range in single electrode type for not much money.
Click to expand...

Thats my first port of call, before spending gazillions on new coils, but knowing my luck the secondarys will be siezed solid
 
Marki_GSA said:
Follow the trace of the O2 sensors. If it is a miss fire should spike rich, if its fuel it should spike weak. The O2 sensor will show the side its all happening at. Its possible if it is just missing once every so often it won't show anything but if you are feeling it then it should show as it is a longer event

Random misfires are rarely fuel and more likely coil or possibly plug.
Click to expand...

These are the options the GS reports on - Lambda control factor (cylinder 1), Lambda control factor (cylinder 2), Knock sensor 1( V), Knock sensor 2( V),

Lambda sensor voltage (cylinder 1)( mV),Lambda sensor voltage (cylinder 2)( mV),

is it any of those

??
 
Sensor voltage will tell you. Head over to the Hexcode site and lookup what the voltages mean and how to use them. You will learn far more there than from me on a forum. Pretty sure someone over there has done a program that will graph the results as well making it really obvious if something is odd.
 
Misfire & data logs

When you have a missfire, fuel injection behaves seemingly strange. The unused oxygen (left over by missing sparks) causes the ECU to add more fuel. This makes the engine run rich often sooting up the O2 sensor.
When it happens on one side the effect is easily proved by swapping coils left/right. When it happens on both sides, the least cost test is to borrow some known good coils.
Just to be helpful, primary coils tend to fail in pairs. Who knows why BMW did not use four identical coils with elbow adapters for the secondaries. But that would be too convenient.
 
In the past I have always used Livegraph for GS911 .csv files & Logworks for other .log files.
 
It's only a suggestion and apologise if useless.


Check the clamps on your throttle bodies and the big clamp at the airbox end of the tube.

Sent from a U11
 
younger06 said:
It's only a suggestion and apologise if useless.


Check the clamps on your throttle bodies and the big clamp at the airbox end of the tube.

Sent from a U11
Click to expand...

If its not raining tommorrow, i will do that, as well as sniff the coils :)
 
Just pulled both primaries

LH Cyl (2 i think) had no smell whatsoever RH (cyl 1?) has a faint oily type smell could be hot, burnt but ive never smelt a bad

one lol

Should i do the secondaries?
 
Bem said:
Usually the secondaries break down first - because they are more exposed?
Click to expand...
It's usually the main coils that fail, not the secondaries
Santa-2512 said:
Just pulled both primaries

LH Cyl (2 i think) had no smell whatsoever RH (cyl 1?) has a faint oily type smell could be hot, burnt but ive never smelt a bad

one lol

Should i do the secondaries?
Click to expand...
. You've data logged information (none of which will tell you if the coils are the problem) and yet you're resorting to smelling the coils :D ... Just unplug the secondary coil connectors and take it for a ride, In fact simply trying to start it may reveal all.
 
Misfire & data logs

In the old days of distributor caps and external coils, people would often fit a new coil while searching out a problem. Almost invariably the coil was not the problem.

Burnt (black painted BMW) primary coils smell so much you’ll notice when the covers are taken off. No smell almost certainly means no (obvious) problem.

My secondary plugs are working (correct tip colour etc) but disconnecting secondary coil wiring connectors makes no difference I can detect.

A failing primary without the support of a secondary spark should make an obvious difference to how the engine runs. Do one at a time.

Get the engine hot and playing up before disconnecting secondaries.
 
Steptoe said:
It's usually the main coils that fail, not the secondaries
. You've data logged information (none of which will tell you if the coils are the problem) and yet you're resorting to smelling the coils :D ... Just unplug the secondary coil connectors and take it for a ride, In fact simply trying to start it may reveal all.
Click to expand...

Hi Neil,

Edit, just realised what you meant - will disconnect the secondarys ;)

Invariably it starts fine and will run fine for xx time then it starts to misfire,
usually its as ive, slowed down or on low throttle / opening back up it appears to be around the 2-3k mark.

I'll get some tools out and take it for a run and let you know ;)
 
Right just been outside - Pissing down :( i'm not going for a run in that lol

Disconnected both secondarys - and tried to start it

A bit hesitant, needed a tiny amount of throttle, but started and ran a bit lumpy for a few seconds 1.2-1.5k , then settled down

into a reasonably smooth idle - 1-1.2K

slightly lumpy on opening the throttle, but that appeared to clear.

Reconnecting both secondarys made no difference

I guess then next step is to disconnect the secondarys and go for a ride
 
Misfire & data logs

All you need is a small flat screwdriver to release the secondary coil cable connectors.
 
Nippy Normans supply Touratech, Wunderlich, Desert Fox and many other makes of accessories.
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