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 Misfire on right cylinder.

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Jason Bailey
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Join date : 2019-11-24

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PostSubject: Misfire on right cylinder.    Misfire on right cylinder.  Icon_minitime1Thu Dec 19, 2019 11:09 am

I tried to search for all similar issues, but could not come up with anything. I have a 15 GRiSO 8v, Mistral pipe, Beetle map. I picked the bike up recently. The right bank is misfiring intermittently, mostly at lower rpms.

I've checked;

1. all fuses

2. caps, boots, wires and coils (all are after market)

3. changed plugs (right one was dark)

4 I tried to connect the computer with the diagnostic program, but it did not connect. The dealer ran into the same issue.

I need to check the valves, but I haven't had time.

Has anyone ran into this connection issue. the bike runs and feels strong at higher rpms. There was a thread about a dead bank, but I couldn't find a connection or a fix .

Any help would be much appreciated.


Last edited by Jason Bailey on Thu Dec 19, 2019 12:29 pm; edited 1 time in total
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kiwi dave
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PostSubject: Re: Misfire on right cylinder.    Misfire on right cylinder.  Icon_minitime1Thu Dec 19, 2019 12:15 pm

Do a search on "Spark Plug Leads" on this forum. Lots of stuff to digest.
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Jason Bailey
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PostSubject: Re: Misfire on right cylinder.    Misfire on right cylinder.  Icon_minitime1Thu Dec 19, 2019 12:27 pm

I read most of them. The first thing I checked was wires and boots. Switched sides, to be sure. The problem didn't follow the wire. they seem to be fine. I'm picking up a tester for the coil, they are pretty new, sub 1000 miles.
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Pete Roper
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PostSubject: Re: Misfire on right cylinder.    Misfire on right cylinder.  Icon_minitime1Thu Dec 19, 2019 12:34 pm

Stick a strobe on the HT leads. That will rule out spark if it isn't just arcing. Are the clips that retain the injector plugs present?
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Jason Bailey
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PostSubject: Re: Misfire on right cylinder.    Misfire on right cylinder.  Icon_minitime1Thu Dec 19, 2019 12:41 pm

I'm grabbing a strobe today. I don't have one. I will take a closer look at the injector when I get home. Thanks.
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kiwi dave
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PostSubject: Re: Misfire on right cylinder.    Misfire on right cylinder.  Icon_minitime1Thu Dec 19, 2019 12:44 pm

Swapping the HT coils over may pin point if it's a coil problem.
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Jason Bailey
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PostSubject: Re: Misfire on right cylinder.    Misfire on right cylinder.  Icon_minitime1Thu Dec 19, 2019 12:57 pm

I did swap wires, at the dealer. It would be hard to pinpoint at home. The PC connector isn't working. I need to rewire maybe? I get nothing to the dio program.
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Kiwi_Roy
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PostSubject: Re: Misfire on right cylinder.    Misfire on right cylinder.  Icon_minitime1Thu Dec 19, 2019 6:19 pm

Do a quick check of the plug leads and connections with your multimeter
[You must be registered and logged in to see this link.]
If you pull off the plug caps the resistance from plug cap to chassis should be the same on both sides, I would guess about 8kOhms, anyway the same on both sides.
This tests the plug cap, leads and coil in one go.
Note:
     I'm assuming this bike only has one plug per cylinder as per the schematic, if its 2 plugs per cylinder you will need to measure Ohms from inner to outer plug cap instead

If you find one side open it probably has that nasty carbon core lead, it sometimes arcs and burns it's way up the cable, a quick fix is poke a strand of wire or a sewing pin up the cable to bridge the gap.

You can also check the leads one component at the time i.e from cap to lead about 5K, lead 5k, coil 3k
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Griso Von
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PostSubject: Re: Misfire on right cylinder.    Misfire on right cylinder.  Icon_minitime1Wed Jan 22, 2020 1:27 pm

My 2016 GRiSO had the valves adjusted at a Dealer out West and they left the ground wire off on the left cylinder, it seemed to run fine but check the ground wire on your individual coils. Dave
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Kiwi_Roy
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PostSubject: Re: Misfire on right cylinder.    Misfire on right cylinder.  Icon_minitime1Fri Jan 24, 2020 9:41 pm

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The two relays 28 and 29 are critical, if either of those drop out for a split second it will play havoc with the running.
Try picking up small lamp preferably 12V LED on the downstream side of the (29) relay contact, Mount the lamp up front on the bars you should see a steady light, no flickering.
If there is anything wrong with (28) relay it will show up at (29) also, you can always go back to that relay to narrow down the fault.
It's probably not going to show anything but at least it will eliminate a couple of possibilities.
I was recently working with a Stelvio owner (almost identical wiring), his bike started cutting out, turned out to be the speed pickup wire pinched shorting the Red/black wire to chassis.


Last edited by Kiwi_Roy on Thu Feb 06, 2020 6:49 am; edited 4 times in total
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Jason Bailey
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PostSubject: Re: Misfire on right cylinder.    Misfire on right cylinder.  Icon_minitime1Sat Jan 25, 2020 10:08 am

I, certainly, would not have thought of that. Thank you..
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Kiwi_Roy
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PostSubject: Re: Misfire on right cylinder.    Misfire on right cylinder.  Icon_minitime1Thu Feb 06, 2020 5:30 am

Look how absurdly simple the wiring of the main components is, sketch it out.
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Starting at the Main Injection Relay (28) from Left to right
Ground to chassis, +12 from ignition switch,+12 from relay to a whole bunch of stuff including ECU pin 17, +12 from Fuse 4. so that relay should be always On the Red/black wire always alive.
Now look at the Secondary Injection Relay (29) from left to right.
Wire from pin 6 of the ECU to the coil, other side of coil from relay (28) we know this is +12 so assuming pin 6 of the ECU is grounded to chassis relay (29) is closed, the red wire on pin 3 will be +12 also
Look what that wire feeds as it goes left,
The fuel pump (35), Right coil (44), Left coil (45), Right injector (46), Left injector (47) so far everything is common to both cylinders and the Voltage should be steady 12 Volts hence my suggestion to monitor this point with a 12 Volt LED, you will easily see if anything is amiss by flickering.
Now look at pin 2 of the coils and injectors, in every case it goes to an ECU pin these pins are pulled to chassis to fire the coil or injector, as long as the wire is intact then we just need to have faith in the ECU firmware. The only thing not common to both cylinders is the coils or secondary leads, measure from the plug cap to chassis on each side, should be around 8k Ohms I think, both the same. If one cap to chassis is open I suggest you have that nasty carbon core lead, I replace it with copper core if ever I find it, Inspect the leads for possible arc to ground. Everything so far is straight forward eh!
So how does the ECU know when to ground the 4 outputs I hear you ask? That's all triggered by the pickup (50)
On the camshaft is a multi tooth wheel with one tooth missing, The ECU looks for that missing tooth in the pulses from (50) then it starts counting, at a certain count it fires the right injector, at another count the right coil, the left injector, the left coil.
I know this is over simplified there's a lot more going on in software that Beetle tweaks to make the bike run better but nothing he will do to make it miss intermittently on one cylinder.
Of course the sensor (50) can be faulty but if its erratic its not likely it will effect one side, more likely to effect both or swap from side to side.

Be gentle on me Mark and I will change this explanation of the ECU accordingly lol
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Kiwi_Roy
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PostSubject: Re: Misfire on right cylinder.    Misfire on right cylinder.  Icon_minitime1Fri Feb 07, 2020 1:38 am

Really the only other suggestion would be to swap the coils to see if the fault moves.
That and examine the connectors 1&2 at each coil and injector under a magnifying glass for any sign of corrosion
Also the connector at the ECU pins 10, 28, 57 & 58 at the ECU These connectors have to pass a lot of current for their size you cannot afford to have any resistance at all.
I'm a big fan of Vaseline on connectors Definitely NOT Di-electric grease although I might spring for a can of Craigs De-oxit in this case
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Kiwi_Roy
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PostSubject: Re: Misfire on right cylinder.    Misfire on right cylinder.  Icon_minitime1Sun Feb 09, 2020 4:47 am

Examine the connectors 1&2 at each coil and injector under a magnifying glass for any sign of corrosion
Also the connector at the ECU pins 10, 28, 57 & 58 at the ECU
I'm a big fan of Vaseline on connectors Definitely NOT Di-electric grease although I might spring for a can of Craigs De-oxit in this case

Re Crank Position Sensor
It could possible be the crank position sensor too far away from the toothed wheel there's a very good article called Efiman that goes into fuel injection. the sensors usually weep oil and sometimes an owner will pull it off and add another gasket gapping it too far. Its hard to check the gap, heres what I do. Take the sensor off and put a small blob of JB Quick on the tip then bolt it back in, give it time to set without turning the engine then take it off and measure how thick the JBW is.
I think if it was a gap problem it might effect one cylinder more than the other because it's further away from the index point (missing tooth)
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This document describes an early fuel injection, although its very old most things still apply.
Page 13, the gap is 0.6 to 1.2mm so its quite forgiving measures 680 Ohms.
These sensors consist of a tiny magnet with a coil wound around it, as the steel teeth pass the sensor they disturb the field creating little AC waveforms which the ECU counts to keep track of where it's at. When it comes to the missing tooth it starts again.
Occasionally these things fail open leaving you dead in the water its not a bad idea to get a spare off ebay or somewhere they are impossible to find when you really need one.

It has to be something really simple, you may fix it and never know what it was
You dont have that nasty carbon core cable do you, I hate that stuff, sometimes it will arc up the cable creating a gap that the spark has to jump, usually shows up under aceleration because its harder to jump across the spark gap under pressure,
If you have 5 k resistor caps you should use copper.
I think if you measure from cap to chassis it should read about 8 kOhms 5 for the cap and 3 for the coil, whatever it is both sides should be identical.
Try running it in the dark just incase there's a leakage to ground from a lead.
Grab the lead in your hand it will let you know if it's leaking but don't run it from arm to arm.
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