misfiring at off idle revs - Triumph Forum: Triumph Rat Motorcycle Forums
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post #1 of 12 (permalink) Old 08-24-2019, 04:05 PM Thread Starter
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misfiring at off idle revs

Hi. My 2010 T100 efi Bonneville, engine number 455750, 18000miles on the clock, started to misfire after a 10 mile run, No engine management light on. I managed to limp back home but at revs above 2000 it misfired badly, though at idle both cylinders fired ok. I had taken on fuel 60 miles ago, a few days ago.
On returning home. I removed seat and tank, checked connectors and spark plugs, the resistance across the 2 coil primary connectors showed 2.7 ohms, the Crank position sensor resistance showed 211ohms at 20 deg C. I do not wish to throw components at it, to get a fix. Any ideas Guys?
ps the battery shows 12.85 volts.

Last edited by triton120; 08-24-2019 at 04:14 PM. Reason: more info
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post #2 of 12 (permalink) Old 08-24-2019, 07:56 PM
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I'm debugging something similar...feels like a misfire but no popping out the back end....most noteable at steady throttle positions at higher revs, cruising along. Bike seems to just instantaneously drop a bit of power then back on. Keeps doing this forever.
I've checked primary coil resistance as 33 Ohms and secondary to plug end of wire caps at 5k Ohms each side.
My next check will be with TuneECU to confirm if throttle valves are in sync. Also will be rechecking for air leaks around intake boots and map sensor rubber connections.

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post #3 of 12 (permalink) Old 08-24-2019, 08:01 PM
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Vacuum leak? what do the plugs look like? The leads sometimes go bad as well.
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post #4 of 12 (permalink) Old 08-26-2019, 02:56 PM Thread Starter
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I checked the Crank Position Sensor today, resistance 211 ohms , put it in boiling water, resistance only went up to 270 ohms. Would you declare it serviceable and look elsewhere or replace it?
The plugs seem ok light straw colour, both the same.
Cheers
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post #5 of 12 (permalink) Old 08-26-2019, 06:33 PM
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I have the same problem only at 3-4k. No help but I can verify any numbers you find. I'm at a loss for these efi bikes.
https://www.triumphrat.net/air-coole...der-25mph.html
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post #6 of 12 (permalink) Old 08-27-2019, 12:21 AM
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I'm going to swap out my coil for a new one. Note that resistance and testing of a coil is not conclusive unless values are out of spec. Coil can perform poorly while riding due to heat or vibrations. Also the high voltages involved can mean internal arcing leading to weakened spark at the plug gaps.
Found a thread on here showing a compatible replacement coil for Honda at less than half price of new triumph part.

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post #7 of 12 (permalink) Old 09-05-2019, 07:56 PM
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Originally Posted by Tornado99 View Post
I'm going to swap out my coil for a new one. Note that resistance and testing of a coil is not conclusive unless values are out of spec. Coil can perform poorly while riding due to heat or vibrations. Also the high voltages involved can mean internal arcing leading to weakened spark at the plug gaps.
Found a thread on here showing a compatible replacement coil for Honda at less than half price of new triumph part.
Well got the new coil installed but I still have the issue. Need to run more checks now....Definitely experiencing a mild "tug" at pretty much all rpms and most noteable while pulling up a long smooth hill with throttle held steady. Can also see a very slight waver on the tacho needle while holding throttle steady at speed and even while released idling.

Will check the ignition pickup coil resistance and try to see if heating coil or jiggling it about makes any difference in resistance. Will also run TuneECU hook up to check throttle balance and other readouts Throttle Position Sensor. Also likely to do a vacuum leak test on all the rubbers into the intake manifold.

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post #8 of 12 (permalink) Old 09-09-2019, 03:31 PM Thread Starter
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Update.... I replaced the Crank Position Sensor as I was changing the oil anyway, still misfiring, changed the spark plugs ...now revs fine. I had previously replaced the plugs 1000miles ago so maybe a duff NGK that l fitt.ed. I now have a spare Crank Sensor!
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post #9 of 12 (permalink) Old 09-09-2019, 05:12 PM
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Originally Posted by triton120 View Post
Update.... I replaced the Crank Position Sensor as I was changing the oil anyway, still misfiring, changed the spark plugs ...now revs fine. I had previously replaced the plugs 1000miles ago so maybe a duff NGK that l fitt.ed. I now have a spare Crank Sensor!
Good to hear. I pulled my plugs and though they looked fairly clean, noted the gaps were under spec (0.8-0.9mm....mine were closed to 0.6mm). Also ordered some 7mm cable and new NGK caps to make up new cable sets (about $20 in parts....not paying through the nose for the triumph store cable sets ($90+ per one).

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Last edited by Tornado99; 09-09-2019 at 05:20 PM.
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post #10 of 12 (permalink) Old 09-20-2019, 04:41 AM
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Well new plugs (Iridium), new HT cables and caps (I ordered the parts and cable separately from on-line places and made them up myself for $15 vs $200 for the Triumph made assemblies). No improvment.

Ran TuneECU today and found the throttles out of balance by 20 hPa...which is the high side of spec. Tweaked the balance screw to get them bang on the same. Also found TPS at 0.62 or 0.63v....and set it to the spec 0.6v. Did what I thought was Adaptation Reset step in TuneECU but didn't recall the proper steps like turning off ign and waiting for TuneECU to signal ready to disconnect (green light going out???). so not sure if it actually reset anything.

Anyway the stumbles/misfires became seriously severe on the first test ride after these changes. Before it was subtle, hard to detect, kinda like going over rough ground. Now it was a severe cough while toodling along city streets at steady throttle. Kept riding for 20-35 min trying to id a throttle position/rpm/speed where the problem occurred frequently. Got to top of a local mountain and had a few coughs around 3k rpm so decided to stop and record on my phone. By time I climbed off bike, got camera recording, I could not get it to reoccur. Got back on and kept riding rest of day and seemed the problem had all but cured itself...rarely detected anymore stumbles/misfires...even the subtle ones. Only thing I can think of....the ECU was re-learning/gathering datapoints which lead to the severe misfires. As I got more time riding these settled down.
I do recall some write up on the adaptation process where there was some mention about requiring a bit of full throttle opening for proper learning to occur. I did a few bits of that today on the highway....

Will need more rides to finally know if this is completely fixed....

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Last edited by Tornado99; 09-20-2019 at 04:44 AM.
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