Riddle me this (misfiring cause)
Discussion
I have just spent a week riding my 2005 ZX6R and what started as an annoying fault ended up making the bike borderline unrideable.
Day 1 - 300 miles, faultless
Day 2 - 300 miles, faultless
Day 3 - after about 100 miles of faultless riding, I do about 50 miles through 30 mph city traffic and it's about 30/35 degrees outside. Water temp around 95-100 degrees, when the fan cuts in. Initially I hear a few splutters from the engine, and then the bike starts to misfire badly, despite a steady throttle it's kangarooing violently until finally the FI light comes on and it dies. I give it half an hour to cool down and it does the remaining 100 miles faultlessly.
Day 4 - 300 miles, faultless
Day 5 - 300 miles faultless, except right at the end, at night, water temp mid 70s riding on flowing roads and the bike starts to stutter again, but only maybe once every 30 seconds, so is still perfectly rideable.
Day 6 - 100 miles in and it starts to stutter again, exactly like on day 5, except it is during the day time and in hot 30 degree sun at altitude, and the bike starts to run very hot.
Day 7 - coolant flushed and replaced, radiator cleaned out and air filter cleaned. Bike seems much happier.
Day 8 - see day 5 except the misfiring only starts after 400 miles.
Day 9 - after 12 hours and 600 miles, the bike starts to stutter, starting with slight misfiring but I need to keep going and nurse it home a further 100 miles, by which point it almost totally unrideable as the kangarooing is so violent and it frequently cuts out, barely able to hold 40mph and with the FI light frequently on. Magically with 10 miles to go, the issue totally goes away and it is totally fine.
The problem started when the bike got very hot on day 3 and was intermittent thereafter. As a result, I had the coolant changed, which significantly reduced its running temperature. However, the misfiring continued. On day 9, I noticed that the problem got worse when riding over heavy bumps, as the bike would cut out at that particular moment, but would then continue to misfire. A relatively successful way of riding around it was instead of holding a steady throttle, to accelerate and decelerate relatively hard on/off every half second or so (that was fun on the motorway).
Any ideas as to the cause? It's an odd one, as the bike almost always seems to run perfectly for the first 6 hours or so of any ride, but then inevitably becomes unrideable. My first thought is either the coils or a short or faulty earth somewhere in the wiring. The problem seems to be linked to (i) running time, (ii) operating temperature and (iii) bumps. Turning the bike off and giving it five minutes seems to temporarily alleviate the symptoms, as does chucking water at the engine and exhaust. I wonder if the hot running on day 3 damaged some wiring and started the problem.
Does this sound like a typical problem linked to the coils? I'd be grateful for any pointers of what to look for before I start poking around the wiring or attacking the b
d bike with a hammer. Would coil damage be visible?
Thanks
Day 1 - 300 miles, faultless
Day 2 - 300 miles, faultless
Day 3 - after about 100 miles of faultless riding, I do about 50 miles through 30 mph city traffic and it's about 30/35 degrees outside. Water temp around 95-100 degrees, when the fan cuts in. Initially I hear a few splutters from the engine, and then the bike starts to misfire badly, despite a steady throttle it's kangarooing violently until finally the FI light comes on and it dies. I give it half an hour to cool down and it does the remaining 100 miles faultlessly.
Day 4 - 300 miles, faultless
Day 5 - 300 miles faultless, except right at the end, at night, water temp mid 70s riding on flowing roads and the bike starts to stutter again, but only maybe once every 30 seconds, so is still perfectly rideable.
Day 6 - 100 miles in and it starts to stutter again, exactly like on day 5, except it is during the day time and in hot 30 degree sun at altitude, and the bike starts to run very hot.
Day 7 - coolant flushed and replaced, radiator cleaned out and air filter cleaned. Bike seems much happier.
Day 8 - see day 5 except the misfiring only starts after 400 miles.
Day 9 - after 12 hours and 600 miles, the bike starts to stutter, starting with slight misfiring but I need to keep going and nurse it home a further 100 miles, by which point it almost totally unrideable as the kangarooing is so violent and it frequently cuts out, barely able to hold 40mph and with the FI light frequently on. Magically with 10 miles to go, the issue totally goes away and it is totally fine.
The problem started when the bike got very hot on day 3 and was intermittent thereafter. As a result, I had the coolant changed, which significantly reduced its running temperature. However, the misfiring continued. On day 9, I noticed that the problem got worse when riding over heavy bumps, as the bike would cut out at that particular moment, but would then continue to misfire. A relatively successful way of riding around it was instead of holding a steady throttle, to accelerate and decelerate relatively hard on/off every half second or so (that was fun on the motorway).
Any ideas as to the cause? It's an odd one, as the bike almost always seems to run perfectly for the first 6 hours or so of any ride, but then inevitably becomes unrideable. My first thought is either the coils or a short or faulty earth somewhere in the wiring. The problem seems to be linked to (i) running time, (ii) operating temperature and (iii) bumps. Turning the bike off and giving it five minutes seems to temporarily alleviate the symptoms, as does chucking water at the engine and exhaust. I wonder if the hot running on day 3 damaged some wiring and started the problem.
Does this sound like a typical problem linked to the coils? I'd be grateful for any pointers of what to look for before I start poking around the wiring or attacking the b
d bike with a hammer. Would coil damage be visible?Thanks
I suspect the initial heating has caused a partial breakdown of some electronic component - could be a sensor, coil as you suspect, ECU possibly (although unlikely).
This then manifests itself when the bike now gets warm rather than super-hot. Might be worth letting it get hot and trying to read error codes from the management.
I'd lay it on a crank/camshaft sensor (as they're directly connected to the engine and therefore get a lot of heatsoak) or a coil.
This then manifests itself when the bike now gets warm rather than super-hot. Might be worth letting it get hot and trying to read error codes from the management.
I'd lay it on a crank/camshaft sensor (as they're directly connected to the engine and therefore get a lot of heatsoak) or a coil.
Bringing this back from the dead, virtual pint to those who said spark plugs - changed them and they did not look in great nick - with rust marks and some deposits.
From a 70 mi test ride, bike seems to run faultlessly, albeit with an FI light that still comes on after half an hour, but I think that's unrelated and due to needing an exhaust servo resistor.
To the extent anyone is interested, I tested the resistance of the coils and got the following readings:
Cyl 1 p 1.8 s 9.27k
Cyl 2 p 1.8 s 9.41k
Cyl 3 p 1.9 s 9.4k
Cyl 4 p 1.9 s 9.45k
The service manual suggests the following readings:
Primary Windings: 1.2 ? 1.6 ?
Secondary Windings: 8.5 ? 11.5 k?
So the secondaries are all in spec but all of the primaries are out of spec, yet they are very consistent. From my limited knowledge I would have thought the secondaries would be more likely to cause problems if out of spec but happy to be corrected. I just think it's unlikely for the primaries to all be out of spec by almost the same amount.
I thought one of the rudimentary tests for a faulty coil was shaking to check for rattles. 3 of the 4 coils rattled when shook, but given the resistance values, not sure if this is a red herring.
From a 70 mi test ride, bike seems to run faultlessly, albeit with an FI light that still comes on after half an hour, but I think that's unrelated and due to needing an exhaust servo resistor.
To the extent anyone is interested, I tested the resistance of the coils and got the following readings:
Cyl 1 p 1.8 s 9.27k
Cyl 2 p 1.8 s 9.41k
Cyl 3 p 1.9 s 9.4k
Cyl 4 p 1.9 s 9.45k
The service manual suggests the following readings:
Primary Windings: 1.2 ? 1.6 ?
Secondary Windings: 8.5 ? 11.5 k?
So the secondaries are all in spec but all of the primaries are out of spec, yet they are very consistent. From my limited knowledge I would have thought the secondaries would be more likely to cause problems if out of spec but happy to be corrected. I just think it's unlikely for the primaries to all be out of spec by almost the same amount.
I thought one of the rudimentary tests for a faulty coil was shaking to check for rattles. 3 of the 4 coils rattled when shook, but given the resistance values, not sure if this is a red herring.
Well it isn't the coils. Chucked a full secondhand set on and the bike was even worse - sounded a little offbeat and was vibey as hell. Then twenty minutes in, the first little hiccough and misfire. It is drastically better than it was last summer but something is still not right.
I am thinking it could be the crank/camshaft sensor but who knows. I will see if I can read the error codes but if that doesn't help it is just going to a shop.
I am thinking it could be the crank/camshaft sensor but who knows. I will see if I can read the error codes but if that doesn't help it is just going to a shop.
Fuel surely??
Maybe the fuel pump is giving in or you have a collection of crud slowly blocking the system.
Intermittent electrical connection to the fuel pump?
Faulty fuel pressure regulator in the pump assembly
if you've changed the coils (why it would run worse?? ) and no difference then I'd be looking at fuel.
If the cam sensor was iffy, it's be so all the time, not after 100's of miles.
Maybe the fuel pump is giving in or you have a collection of crud slowly blocking the system.
Intermittent electrical connection to the fuel pump?
Faulty fuel pressure regulator in the pump assembly
if you've changed the coils (why it would run worse?? ) and no difference then I'd be looking at fuel.
If the cam sensor was iffy, it's be so all the time, not after 100's of miles.
Blocked fuel cap vent is an interesting one - not sure it fits with how the bike feels but will take a look.
Clearly from my rambling I have no clue so am just fumbling in the dark and searching for ideas before I chop it in! My next step will be to read the codes and see if there is anything in there, but just thought I would put it up here in case anyone had any bright ideas or to help anyone having similar issues.
No idea why the coils have made it run a bit worse - surely you have spark or no spark - but it just felt significantly rougher and more vibey as soon as I started it. I do think the TBs need balancing which won't help, but this could only be related to changing the coils as that was the only variable (aside from me checking the plugs and putting them back in). I found that although they are identical the replacement (used) coils did not seat as securely as the original ones, as you could pull them out with one finger. Doubt that is related though?
The trouble I am having is that I think there are two separate things at play. I am pretty sure the violent misfiring last year was just the plugs as that has not replicated itself since changing them and the bike does seem happier . I thought it was fixed until it died in traffic at 103c the other week. But equally it was fine in traffic yesterday after I changed the coils. So although the bike is not running as well, the cutting out may have been due to the coils. I noticed one of the coils had a small area that had melted part way down, so maybe that was it. I don't know. That's the problem - it is so intermittent it is making it hard to diagnose.
Aside from the cutting out and violent misfiring, there is a secondary, possibly related, possibly not, underlying issue where it is not quite running right and has the occasional misfire, and this is what I am now trying to sort out. One thing I have noticed before and dismissed, but which might be relevant, is that on a steady throttle you can sometimes hear a very very subtle popping from the exhaust almost as if you are on the overrun (except this is when you have throttle on). It's very subtle, to the extent I have previously dismissed it, but I am wondering if I am not imagining it, and there is something wrong that is constant rather than intermittent. And I feel like if so, then it is connected to the misfire. It's almost as if it's just constantly running way way too rich. Except the plugs and exhaust look good.
One thing I did notice is that it does have an exhaust servo eliminator fitted by the previous owner. If it's a cheap ebay jobby and is failing, I wonder if that could cause these issues?
Just from the feel of it, it seems more electrical than fuel-based. But of course, as suggested above, it could be the vent cap, so at least I have narrowed it down to just spark, fuel or air
Steve Bass said:
Fuel surely??
Maybe the fuel pump is giving in or you have a collection of crud slowly blocking the system.
Intermittent electrical connection to the fuel pump?
Faulty fuel pressure regulator in the pump assembly
if you've changed the coils (why it would run worse?? ) and no difference then I'd be looking at fuel.
If the cam sensor was iffy, it's be so all the time, not after 100's of miles.
Well if I knew what it was, I wouldn't be writing here Maybe the fuel pump is giving in or you have a collection of crud slowly blocking the system.
Intermittent electrical connection to the fuel pump?
Faulty fuel pressure regulator in the pump assembly
if you've changed the coils (why it would run worse?? ) and no difference then I'd be looking at fuel.
If the cam sensor was iffy, it's be so all the time, not after 100's of miles.
Clearly from my rambling I have no clue so am just fumbling in the dark and searching for ideas before I chop it in! My next step will be to read the codes and see if there is anything in there, but just thought I would put it up here in case anyone had any bright ideas or to help anyone having similar issues.No idea why the coils have made it run a bit worse - surely you have spark or no spark - but it just felt significantly rougher and more vibey as soon as I started it. I do think the TBs need balancing which won't help, but this could only be related to changing the coils as that was the only variable (aside from me checking the plugs and putting them back in). I found that although they are identical the replacement (used) coils did not seat as securely as the original ones, as you could pull them out with one finger. Doubt that is related though?
The trouble I am having is that I think there are two separate things at play. I am pretty sure the violent misfiring last year was just the plugs as that has not replicated itself since changing them and the bike does seem happier . I thought it was fixed until it died in traffic at 103c the other week. But equally it was fine in traffic yesterday after I changed the coils. So although the bike is not running as well, the cutting out may have been due to the coils. I noticed one of the coils had a small area that had melted part way down, so maybe that was it. I don't know. That's the problem - it is so intermittent it is making it hard to diagnose.
Aside from the cutting out and violent misfiring, there is a secondary, possibly related, possibly not, underlying issue where it is not quite running right and has the occasional misfire, and this is what I am now trying to sort out. One thing I have noticed before and dismissed, but which might be relevant, is that on a steady throttle you can sometimes hear a very very subtle popping from the exhaust almost as if you are on the overrun (except this is when you have throttle on). It's very subtle, to the extent I have previously dismissed it, but I am wondering if I am not imagining it, and there is something wrong that is constant rather than intermittent. And I feel like if so, then it is connected to the misfire. It's almost as if it's just constantly running way way too rich. Except the plugs and exhaust look good.
One thing I did notice is that it does have an exhaust servo eliminator fitted by the previous owner. If it's a cheap ebay jobby and is failing, I wonder if that could cause these issues?
Just from the feel of it, it seems more electrical than fuel-based. But of course, as suggested above, it could be the vent cap, so at least I have narrowed it down to just spark, fuel or air
Edited by Deranged Granny on Monday 29th June 13:29
Edited by Deranged Granny on Monday 29th June 13:32
Deranged Granny said:
Blocked fuel cap vent is an interesting one - not sure it fits with how the bike feels but will take a look.
Clearly from my rambling I have no clue so am just fumbling in the dark and searching for ideas before I chop it in! My next step will be to read the codes and see if there is anything in there, but just thought I would put it up here in case anyone had any bright ideas or to help anyone having similar issues.
No idea why the coils have made it run a bit worse - surely you have spark or no spark - but it just felt significantly rougher and more vibey as soon as I started it. I do think the TBs need balancing which won't help, but this could only be related to changing the coils as that was the only variable (aside from me checking the plugs and putting them back in).
The trouble I am having is that I think there are two separate things at play. I am pretty sure the violent misfiring last year was just the plugs as that has not replicated itself since changing them and the bike does seem happier better. I thought it was fixed until it died in traffic at 103c. But equally it was fine in traffic yesterday after I changed the coils. So although the bike is not running as well, it might have stopped cutting out now? I don't know. That's the problem - it is so intermittent it is making it hard to diagnose.
Aside from the cutting out and violent misfiring, there is a secondary, possibly related, possibly not, underlying issue where it is not quite running right and has the occasional misfire. One thing I have noticed before and dismissed, but which might be relevant, is that on a steady throttle you can sometimes hear a very very subtle popping from the exhaust almost as if you are on the overrun (except this is when you have throttle on). It's very subtle, to the extent I have previously dismissed it, but I am wondering if I am not imagining it, and there is something wrong that is constant rather than intermittent. And I feel like if so, then it is connected to the misfire. It's almost as if it's just constantly running way way too rich. Except the plugs and exhaust look good.
One thing I did notice is that it does have an exhaust servo eliminator fitted by the previous owner. If it's a cheap ebay jobby and is failing, I wonder if that could cause these issues?
Just from the feel of it, it seems more electrical than fuel-based. But of course, as suggested above, it could be the vent cap, so at least I have narrowed it down to just spark, fuel or air
Remember that faults in the EFI system feel very different to how they feel on a set of carbs. Steve Bass said:
Fuel surely??
Maybe the fuel pump is giving in or you have a collection of crud slowly blocking the system.
Intermittent electrical connection to the fuel pump?
Faulty fuel pressure regulator in the pump assembly
if you've changed the coils (why it would run worse?? ) and no difference then I'd be looking at fuel.
If the cam sensor was iffy, it's be so all the time, not after 100's of miles.
Well if I knew what it was, I wouldn't be writing here Maybe the fuel pump is giving in or you have a collection of crud slowly blocking the system.
Intermittent electrical connection to the fuel pump?
Faulty fuel pressure regulator in the pump assembly
if you've changed the coils (why it would run worse?? ) and no difference then I'd be looking at fuel.
If the cam sensor was iffy, it's be so all the time, not after 100's of miles.
Clearly from my rambling I have no clue so am just fumbling in the dark and searching for ideas before I chop it in! My next step will be to read the codes and see if there is anything in there, but just thought I would put it up here in case anyone had any bright ideas or to help anyone having similar issues.No idea why the coils have made it run a bit worse - surely you have spark or no spark - but it just felt significantly rougher and more vibey as soon as I started it. I do think the TBs need balancing which won't help, but this could only be related to changing the coils as that was the only variable (aside from me checking the plugs and putting them back in).
The trouble I am having is that I think there are two separate things at play. I am pretty sure the violent misfiring last year was just the plugs as that has not replicated itself since changing them and the bike does seem happier better. I thought it was fixed until it died in traffic at 103c. But equally it was fine in traffic yesterday after I changed the coils. So although the bike is not running as well, it might have stopped cutting out now? I don't know. That's the problem - it is so intermittent it is making it hard to diagnose.
Aside from the cutting out and violent misfiring, there is a secondary, possibly related, possibly not, underlying issue where it is not quite running right and has the occasional misfire. One thing I have noticed before and dismissed, but which might be relevant, is that on a steady throttle you can sometimes hear a very very subtle popping from the exhaust almost as if you are on the overrun (except this is when you have throttle on). It's very subtle, to the extent I have previously dismissed it, but I am wondering if I am not imagining it, and there is something wrong that is constant rather than intermittent. And I feel like if so, then it is connected to the misfire. It's almost as if it's just constantly running way way too rich. Except the plugs and exhaust look good.
One thing I did notice is that it does have an exhaust servo eliminator fitted by the previous owner. If it's a cheap ebay jobby and is failing, I wonder if that could cause these issues?
Just from the feel of it, it seems more electrical than fuel-based. But of course, as suggested above, it could be the vent cap, so at least I have narrowed it down to just spark, fuel or air
EFI fuel pressures are important as a drop in pressure effectively leans out the motor. Popping would be a sign of a lean condition so you may well have an intermitent fault in either the pump asseembly itself, wiring to the pump or a positive feed to the injectors (-ve switched at ECU) amongst other things.
Definitely read the codes and report back.... stat
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