Misfiring under acceleration

My Yami was worse under load too. It seems the more physical stress on the bike, the worse the contact of the wires. Espacially because my fuse box was directly under the seat, so as I slid back on the seat while accelerating, the wire pulled away from the box.

 

I'm going to have to agree with Bubba. Every intermittant issue I've had in a vehicle - '89 Buick, a '74 and '75 Fiat (ok, those don't really count), '94 FZR, and a couple of others - all came down to the voltage regulator/rectifier.
The easiest way to check the regulator is to put a voltmeter across the battery when it is running and when it isn't. Also run through the RPMs a little while looking at the voltage. If the voltage doesn't change at any point and is the same as when the bike isn't running, you might want look into replacing the voltage regulator. I believe they have a reputation for being problematic.

 

Hey guys, thanks for all the advice so far. I had replaced the spark plugs about 3 months ago, I do have a K&N aircleaner and I reoiled it, but did so after the problem started happening.
A few weeks ago I was checking all the spark plug leads and one of them was a bit dodgy, had some melted spots in the lead, so I replaced that last night (Honda had none in Australia and had to order from Japan which took 3-4 weeks >_< ) but that didn’t solve anything.
So I did a quick check of the voltage regulator the way RGonVRF suggested.
I checked the battery voltage when the bike was off - 12.81v and when the bike was on - 14.23v. The voltage did not change when I reved the bike apart from a .02 drop in voltage occasionally. I also checked it while the headlights were on highbeam (as the manual suggests) and it didn't make any difference.
So could this be a problem?

 

I have been leaning towards a coil issue. It is an ignition system malfunction issue. A misfire means that the fuel charge is igniting, just not correctly.

 

Norcal, thats why I thought a fuel map problem initially, as it was only happening above 5000rpm and with the throttle wide open. They it started happening occasionally at lower engine speeds and throttle positions. Then there was the instance when the bike just cut out all together.

 

Not sure if this is relevent or not, but while the bike is running on choke, I usually set it to about 2000rpm til it warms up. The idle is usually a bit rough, it will hover around 2k but move +/-100rpm or so.
Just some extra info I thought I'd add.

Anyway, I just checked all the spark plugs and they are still looking good. I tested the coils according to the manual which states the peak voltage should be 100V minumum! I can only assume the coil boosts the battery voltage to this figure. Anyway, the voltage actually dropped to about 10.3v when cranking the engine over. i don't have a peak voltage attachment for my multi, so not sure if this would make a difference???

 

Something else to consider, you could have an intake or vacuum leak. Maybe you have already checked but I would look at all your hose connections and
also your carb. to intake connections and any clamps that are in the circuit. eddie

 

Hey Eddie, no vac leaks as far as I can see, I've cheked everything to do with that.

Yesterday, after checking the coils I went to start the bike and it wouldnt fire up - I got an error code for the IAT sensor (again). The fact that this error keeps popping up can't be ignored despite the sensor itself already having been replaced. So I started testing the wiring by wiggling it around while monitoring the voltage coming from the IAT CONNECTOR PLUG. This produced some interesting results - the voltange would intermittently (yes everything here is intermittent) drop when wiggling it, so I inspected the wiring as far as I could see (up to the point where it joins into the loom) and found no defects. I haven't been able to reproduce the voltage drop again since this morning, but there was definitly a voltage drop this morning.

Just wondering if VFRs have been known to misdiagnose problems? I.e send an error code form one sensor, when really something else is wrong?

 

I think you may have found at least part of your problem. In most cases the ECU has know way of knowing if its the actual sensor or the wiring going to/from it. All it knows is that its getting the wrong signal. Since you are seeing different voltages at the plug when moving the wires around, I would start looking at individual wires and work my way from the plug back toward the power source. Look closely where the wires are joined by connectors. Hopefully you can find it with out digging too much deeper.

Action

 

Didn't we have a post a little while back about a wiring harness issue that caused a full blown melt down. It started as a battery issue, then moved to other components in the electrical and was due to the regulator sending too much voltage and burning out the harness.

This doesn't sound like the exact same problem, but if it is in the main harness it can build heat and catch fire rather easily. I know unwraping the main harness is a pain but I think that would be my next place to look for a problem. Check for melted or discolored insulation, if a wire has been over heated it won't transfer voltage properly and will build up heat.

I hate trying to sniff out electrical issues.

 

You and me both. But I think that is my next target.

 

Hey guys.
The bike is currently sitting at the mechanics awaiting a good once over to see if we can nip this in the butt.

A few weeks ago I went out and pulled the whole bike apart and went to town with my multi-meter. Not surprisingly, I discovered a hiccup in the IAT sensor. I found, that furiously wiggling the wires around made the resistance reading fluctuate. Of course this was very intermittent (as all things are), and eventually by the end of the day, no ammount of wiggling of wires would make the problem reoccur, as if the problem had just solved itself.
Anyway, I inspected the wiring as far as I could see (up to where it bundles in with the loom) and found no defects. i decided to put the bike back together after deciding that there was no more that I could do.

For weeks the bike seemed to be free of problems, somehow by pulling all the wires and connections I'd fixed it. Now the bike runs perfectly 99% of the time. It doesn't jolt or missfire at more than 5k rpm or when I hit pot holes. However, every so often, maybe once every...200-300km, for no apparent reason the bike will just cut out voilently while open throttle.

So I've dumped it at the mechanics and told them to look over the IAT sensor circuitry.

 

How would you check if a coil was bad? do they lose insulation as they age, eg shorting out to the frame? my no 3 coil I think it is ( be at your left knee sat on the bike) appears to be shorting out 'sparking' to the frame when checked by a mechanic mate using a screwdriver across the coil almost touching the frame, he can see a spark from it and reckons that could be why my bike is running fairly bad, slight miss and just not taking the throttle clean. I have fitted new plugs, full service recently.

 

Too bad OP didn't come back and give more info on this issue.

Refer to manual on how to test coils. You measure resistance of primary and secondary terminals. If mechanic can't provide concrete measured numbers, best to find more qualified one.

Can you provide more detail on how mechanic is testing with screwdriver? Does he take hi-tension wires off first before using screwdriver? If not, it just means you have cracks in hi-tension wires that allow high-voltage to short to frame. One easy way to test for this is run bike at night and look for sparks along hi-tension wires. This shows areas with cracks and escaping high-voltage.

As mentioned in this thread and elsewhere, ignition system is fairly robust. More likely you have calibration or wiring issue with some sensor: AIT, TPS, TPS idle-switch, MAP, ECT, etc. This causes ECU to receive incorrect data about environmental and engine conditions. Thus calculating incorrect fuel & ignition values. Each and every sensor has test-procedure in manual that will confirm sensor is good or bad or just mid-adjusted.

Does bike run better after warm-up?
What non-stock mods do you have on bike?
OP has PowerCommander which is source of issue in +80% of cases like this. Bad installation or bad programming. Removing it typically restores it to working perfectly fine like bike just off showroom floor.

 

Thanks, no he disconnected nothing, just layed the screwdriver across the top of the coil almost touching the frame, he would shield his eyes and said it's sparking/shorting to the frame, he reckoned that coil was bad, he checked the other 3 coils the same way and they weren't doing it, this guy has 30 years experience so I think he must know what he's at.
I'm a bit lost otherwise, there would be other mechanics/shops I could try I suppose I will have to find someone that can find what's wrong,
the bike runs bad warm or cold, it's like as if you had dirty fuel or a bad plug at times, hard to explain, just not running as clean as it should,
recent oil and filter, air filter, new iridium plugs, ran some Redex fuel cleaner through a few tanks of petrol, I also fitted a new chain and sprockets last week, I thought some of the roughness I was feeling coming through her was being caused by a worn front sprocket causing vibration that was amplified at speed,
which are the high tension wires? there's 2 wires I see going into the coil and the spark plug lead comes out the other side.

 

hi-tension = spark-plug wires. They should have cap at coil end that makes sealed connection to coil. Maybe new spark-plug wires are needed if they're leaking. Measure coil first.

• EFI is very sensitive to vacuum-leaks. Spray carb-cleaner around manifold boots at head to see if engine-note changes or idle-speed.
• Verify TPS closed-angle and idle-switch. Measure TPS-output voltage from closed to WOT.
• Measure IAT/ECT resistance from freezer, then in water-pot at room-temp and brought up to boiling. These provide fuel-enrichment compensation based upon air and engine-temps.

Basically go through manual and do test-procedure for all sensors.

 

Thanks, that's double dutch to me really, I'll ask a man who knows well hopefully he knows more than me about it which is nothing, do you need the tank up to get at the manifold boots with spray? must sync the starter valves too, trouble here is finding a mechanic that's any bloody good, they all want easy work, quick buck/simple servicing or fitting new parts.

 

For anyone reading this thread in future, found and fixed the problem myself, it was all caused by a vacuum leak. thanks for the help.

 

Where was leak? How did you find it?

 

It was as simple as looking under the tank, a vacuum pipe was just disconnected somehow, refitted it and the bike is running perfect now.
I had looked at everything, coils, plug leads, fitted new plugs etc, still all is good now, if only we had the weather to ride.