Misfiring Problem

[Guest Rock]

Hey guys,

I've had a problem with my bike for quite some time now. It seems to come and go intermittently and the symptoms have changed relatively as well over the past 2 years. The problem causes the bike to misfire. It seems to be relative to the engine temp and to a lesser extent the ambient air temp. The bike seems to run best at cooler temps, from 35 - 75C, V.Smooth idling, good power delivery through rev range etc. After 75C things start to go a bit funny.

At the moment once the bike gets over 75-80C, the idle starts to get a bit jumpy, and when I rev the bike slowly, between 2k-3.5k it misfires quite noticably. And power delivery can be quite sluggish, almost as if it is running way too rich. Once it gets to about 4000rpm it runs fine. I've recently changed the spark plugs, cleaned the air filter and ran a batch of injector cleaner through the tank <- the injector cleaner made it run really bad actually. At the moment I'm not getting any ECU error codes.

I'm not really sure if this is the same issue with new symptoms or if it is completely unrelated:

About 2 years ago the bike had a problem that caused it to misfire and cut out after 5000rpm when accelerating heavily. It gave an error code indicating that the Air Intake Temp (AIT) sensor was faulty. I checked it with a multimeter and it tested fine, but I replaced it anyway. I also tested the wiring to it and that was fine as well.

After replacing the AIT sensor the problem persisted and I kept getting the same error code. After getting the bike checked by a EFI specialist, they still couldnt find the problem. But eventually the problem just resolved itself. Since then I have only had the bike misfire once or twice when accelerating heavily, and it is usually in very hot temps and after about 1 hour + of riding time.

The bike is a '99 VFR800, done about 75,000km. It has a Power Commander 2 and runs on a downloaded 'best fit' map. A staintune can only, and a K&N air filter. It seems to run best on 91RON fuel, 95 and 98RON fuels make it run like shit, with very poor ecconomy and performance, as well as spluttering and misfiring. I've tried running the bike on the factory ECU but the same problems persist.

I'm wondering if anyone else has had any similar experiences and what they've done to fix them?

I'll be keeping the bike for another year before I go overseas so I may invest in getting the PC2 tuned properly on a dyno if that is likely to fix the problem but I'm not really 100% sure that it will.

[enzed_viffer]

I'm wondering if anyone else has had any similar experiences and what they've done to fix them?

If you do a search, you'll find the same problem, listed under various guises.

The guts of it seems to be that the EFI/ECU system is very finickety, and the sensors only need a slightly poor connection, or a bit of crud on a plug in the wiring system, or whatever, to make the ECU give the wrong fueling to the engine.

Rather than reinvent the wheel, take a look at this link.

Basically, you need to check all the connectors for all the sensors, check your grounds (especially the ones under your right knee and left thigh when you're sitting on the bike), and it may help if you add a new ground from pin B1 on your ECU, and another one to the earth cluster under your left thigh. Cleaning contacts in the sidestand switch, ignition switch, and the plugs on the PCB behind the instruments may also help.

The bad news is, I've done all this and more, and while I still have a couple of plugs to do, it hasn't really fixed anything yet. The bike's stopped randonly cutting out, but I still get it misfiring at small throttle openings when the temperature gets over 90C.

Good luck!

[Guest]

Hey mate thanks for the info, albeit relatively bad news :P

Looks like I've got a big job a head of me. The link you provided doesn't really sound relevant to what I'm currently experiencing though, but it's probably worth checking the earth blocks anyway.

Here's an update.

Hey guys, for the past few days the bike has been running perfectly to and from work, this just highlights the intermitent nature of the problem, sometimes its good, other times its bad.

But last night when I started it, it began running rough (probably a better description as I don't really think its a true 'misfire' as if one cylinder isn't firing) straight away. I had the choke on at about 2000rpm and it just kept fluctuating between 3k and 1.5k. One thing to point out is I could actually hear a very fast 'clicking' noise, like the sound a BBQ ignition switch makes when you open the gas valve, coming from the left (when sitting on the bike) rear cylinder, each time the idle would drop off. It was loud enough to hear from a few meters away from the bike, even over the sound of the exhaust. I assume it was the sound of the spark plug firing, but I just thought that was really odd.

When the bike was about 45C I shut the choke off and started riding, and it was idling really bad and very sluggish until just over 3000rpm. Now here's another weird thing, I was almost home, and the temp was about 77C when out of no where the bike just starts running smoothly again like there's nothing wrong.

What the hell did Honda do to give these bikes such annoying problems!

[enzed_viffer]

The "very fast clicking noise" could be the injector. Perhaps it's sticky, or the connector to it isn't very good (but not bad enough to cause the FI light to be illuminated).

[Guest]

Yes it did sound very injector-pulse-like actually. I assumed it was a spark plug, but it was probably too 'fast' for that. The funny thing is I've never heard that sound before on this bike, and I'm pretty tuned in to strange and odd noises coming from engines.

I've just run a batch of injector cleaner through it, so I assume that helped unclog them. As for the injector clip/connector I'll squirt some contact cleaner, but I'm not convinced this clicking sound is directly related to the main problem, though it could be a factor.

I've just read through your 'whats wrong widdit?' thread in its entirety, give's me a few areas to look at.

I actually just remembered a possibly important piece of info. Back when the FI light was convinced that the AIT sensor was farked, the bike would also misfire when riding over a significant bump or pothole, and I accidently discovered that wiggling the wires around the AIT would make the engine cut out, if wiggled with enough force. I didn nothing in particular to fix this, it just kinda stopped misbehaving in this way.

[marks152]

Yes it did sound very injector-pulse-like actually. I assumed it was a spark plug, but it was probably too 'fast' for that. The funny thing is I've never heard that sound before on this bike, and I'm pretty tuned in to strange and odd noises coming from engines.

I've just run a batch of injector cleaner through it, so I assume that helped unclog them. As for the injector clip/connector I'll squirt some contact cleaner, but I'm not convinced this clicking sound is directly related to the main problem, though it could be a factor.

I've just read through your 'whats wrong widdit?' thread in its entirety, give's me a few areas to look at.

I actually just remembered a possibly important piece of info. Back when the FI light was convinced that the AIT sensor was farked, the bike would also misfire when riding over a significant bump or pothole, and I accidently discovered that wiggling the wires around the AIT would make the engine cut out, if wiggled with enough force. I didn nothing in particular to fix this, it just kinda stopped misbehaving in this way.

the clicking you can hear could be a plug lead arching across somwere, seen this a few times on bikes ive had in the past, when its dark you can actually see it arching, flashes of blue light will come from the lead and earth to the nearest peice of metal, id check your plug leads give them a good spray with some silicone spray, it would be sluggish if a plug lead was breaking dow,

[enzed_viffer]

You mean the IAT (Inlet Air Temp) sensor? When you wiggled the wires, was the bike stationary?

I haven't yet found out what's wrong with my bike, and haven't tried wiggling things to try to replicate it. It's a funny one - it first manifests itself when the bike gets hot when commuting, and then only at constant(ish) revs, and once it's done that, it will do it again the next day when the bike isn't hot. I have a suspicion it's not as bad when the tank is full, but haven't verified this yet.

The link I posted may not have seemed relevant, but it seems that almost all the misfiring or other misbehaviour with the VFR are due to something dodgy in the wiring somewhere in the whole ECU/EFI system. Unfortunately, this encompasses almost the whole wiring system, as the components are spread over the whole bike, and there are very many of them: sensors, ECU box, ignition components, injectors, cutout switches, relays, connectors, grounds, etc etc. It takes only one wire somewhere with an intermittent or poor connection, and the engine won't run at 100%.

[Baileyrock]

I actually just remembered a possibly important piece of info. Back when the FI light was convinced that the AIT sensor was farked, the bike would also misfire when riding over a significant bump or pothole, and I accidently discovered that wiggling the wires around the AIT would make the engine cut out, if wiggled with enough force. I didn nothing in particular to fix this, it just kinda stopped misbehaving in this way.

Hey mate,

This is a problem, sounds like a broken wire or shorting wire that needs to be found and fixed first, then go on to further troubleshooting if there's still one after this repair. btw a shorting electrical arch can sound just like a clicking.

Secondly have to tried disconnecting the PC? PC's can also be the cause of many issues and you should always eliminate it as a possibility before moving on to stock parts. You should have NO issues at all just changing fuel octane, stock or PC'ed!!! :huh:

Good luck and welcome. :beer:

[Guest]

Baily dc'ing the PC was one of the fist things I tried, it made no difference, only making the bike feel less exciting :P

I replaced the AIT sensor as a precaution when the problem first started and it made no difference either, infact the FI light just kept telling me there was a problem with it. I traced the wires of the AIT back as far as I could see where they join into the loom and they appeared to have no imperfections. I also took to the AIT and the wiring with my multimeter and everything seemed fine, except when I wiggled the wires as per my above post.

I might start looking there again to see if after 2 years the AIT phantom has returned.

Now, here is another update after the weekend:

I haven't had a chance to do any work on the bike yet but the problem has changed somewhat. Heat no longer seems to be a factor. The misfire seems to be a lot more predominant and it occurs right from when I start the bike, and does not rectify itself as it warms up. (Speaking of, the previous owner replaced the R/R about 20,000km ago, just before I bought it), where as it used to only occur when the bike gets hot.

It also backfires a bit now. In about 5 hours if riding over the weekend I probably heard a really loud backfire a 3 or 4 times. And although rare, I've had the bike almost cut out completely a couple of times, like I watched the tacho needle drop from 5rpm down to 2rpm and back up a few times while taking off from the lights.

Apart from that, the problem is still occurring only between idle at 1.5rpm to 3rpm.

Since Thursday I've ridden in a handful of times and I keep hearing this clicking noise, it is definitely coming from the left rear cylinder (not sure what number this is off hand), and I can't hear it from any other cylider. As I said in the above post, I can only hear the clicking noise as the misfiring/spluttering happens.

I may have to put the bike off the road for a bit while I slowly pull it apart and put it back piece by piece over the next few after-work evenings. Unfortunately I just moved into a new apartment that doesn't have a garrage (was almost a dealbreaker) so I have to hope the weatehr is good.

[Guest]

Ok I found the source of the clicking noise, it is definitely spark arching, and it seems to be coming from the left rear spark plug cap and grounding to the cam cover, I could see it in low light.

So my question is how do I fix this? just buy a new plug lead and cap?

[enzed_viffer]

Ok I found the source of the clicking noise, it is definitely spark arching, and it seems to be coming from the left rear spark plug cap and grounding to the cam cover, I could see it in low light.

So my question is how do I fix this? just buy a new plug lead and cap?

That should fix it. I had a similar problem on my VTR1000 - it misfired badly in the rain, which turned out to be a very small tear in the plug boot. I couldn't see how the water could get in there deep in the hot plug well, but I replaced it anyway, and the problem disappeared.

[Guest]

Thanks enzed. So I'll just replace the cap/lead combo, may have to sell the bike to finance this however, Honda seem to think they are diamond tipped or something. :fing02:

Just had a thought, you mentioned rain, I recently took the bike to a self serve car wash and gave it a good scrub. When I was rinsing it I tried my best not to spray directly towards any openings or gaps where the engine is exposed but I couldnt help some water making contact, especially through the gap between the tank and the metalic frame where you can see the rear bank cam cover. I know most bikes are very water resistant by design but could this cause problems...considering this was over two weeks ago now and should have well and truely dried out?

[enzed_viffer]

When I was rinsing it I tried my best not to spray directly towards any openings or gaps where the engine is exposed but I couldnt help some water making contact, especially through the gap between the tank and the metalic frame where you can see the rear bank cam cover. I know most bikes are very water resistant by design but could this cause problems...considering this was over two weeks ago now and should have well and truely dried out?

Yeah, it should have, especially given how warm it gets at the rear of the engine.

I've never taken any particular care when washing the bike (although I don't use a high-pressure hose), and never had any problems. All I do is start the bike up when I've finished, to make sure it's OK and to dry out things a bit.

[Guest]

Hey guys, the ride to work this morning was like a ride through heaven, at idle the needle sat on 1.300rpm like it was stuck on with glue, and the bike responded without hesitation right through the rev range.

Last night I inspected the spark plug cap and at first couldn see anything, but when I flexed it I could see the tiniest hairline spit in the rubber casing on the side that sits facing the engine. It looked like someone had firmly scraped across it with a very thin razor blade, hardly visible. I have temporarily fixed it just be squeezing the split together and it seems to be holding up. I'll still replace the cap obviously but as these things seem to have horrendously long order delays from Honda it will do in the meantime. But yeh, this morning the bike rode like a dream.

I'd say what was originally happening was the slit would open up when the rubber gets hot and flexible, exposing just enough wire to make the spark jump intermitently, also being affected by bumps in the road surface etc.

This still leaves the AIT sensor issue unaccounted for, but we'll just call than an x-file until it happens again.

 

Enzed, unless you've already done so, I'd suggest you check out your plug leads.

[enzed_viffer]

Hey guys, the ride to work this morning was like a ride through heaven, at idle the needle sat on 1.300rpm like it was stuck on with glue, and the bike responded without hesitation right through the rev range.

Fantastic! :biggrin:

Last night I inspected the spark plug cap and at first couldn see anything, but when I flexed it I could see the tiniest hairline spit in the rubber casing on the side that sits facing the engine. It looked like someone had firmly scraped across it with a very thin razor blade, hardly visible.

That's the same as the issue I had with the VTR! Except on that, it looked as though someone had poked the sparkplug terminal into the plug boot and torn it. I couldn't see how this would affect it, but evidently, it did. The weird thing is I wouldn't even have found it, but was on the Superhawk forum and another owner had the same problem, his mechanic replaced the plug cap, and all was sweet again.

Yeah, I'll check my leads - one thing I haven't done. I'm almost maybe fairly positively hesitantly sure that it's something electrical, and the plug caps/leads are one thing I haven't checked. Should have done it when I replaced the plugs. The misfire or whatever it is, always happens when the bike is at higher than normal running temperature (over 90C), but sometimes when it's cooler, and only does it when on a constant throttle. This made me think maybe it's related to the O2 sensor eliminators, but I checked them and they're fine.

I must also unplug the PCII once again, just to confirm to myself once more that it's not a problem (and to get some warm fuzzies about how much it improves the fueling!)

[Guest]

I must also unplug the PCII once again, just to confirm to myself once more that it's not a problem (and to get some warm fuzzies about how much it improves the fueling!)

Yeh I sometimes need reminding as well, it's easy to get used to the performance until you have something to compare it with.

Well I'm hoping this is the end of it for my bike, and fingers crossed you find a split as well somewhere.

The misfire or whatever it is, always happens when the bike is at higher than normal running temperature (over 90C), but sometimes when it's cooler, and only does it when on a constant throttle.

Exactly the same for me except for constant throttle, mostly only occurs at low revs or idling and sometimes cuts out at higher revs; almost kicking you off the bike in the process.

[Guest]

Hey guys,

I replaced the plug cap on the weekend and the bike is running great now. It has no idling issues and runs really smooth. I did however rev the bike up very slowly to see if there were any problem areas and if I hold the revs at about 4000rpm, the needle does gently move around like it can't quite find where it should be. It's nothing like it used to be, but it is still noticeable compared to the rest of the rev range. It only seems to be an issue when free reving, it doesn't have any noticeable effect when riding, so unless it worsens and becomes a problem, I'm pretty happy to live with it, unless someone can suggest an easy fix of course.

[Guest]

It happened again! But I think I know where to start looking now.

Well today the temp reached a steamy 40 degrees. The bike started up normally and was running normally until I had to sit in some gridlock traffic and the bike started to get hot. It got up to 95C when I took off through an intersection and it just started running like an angry dog, spluttering, misfiring, jolting, etc. The tacho needle was bouncing up and down like crazy. I had to pick some stuff up on my way home from work so I kept riding for a bit and the bike just kept misbehaving. On throttle, off throttle, high revs, low revs, it was just going berserk no matter what I did. Anyway, I gave the bike a big rev and hit red-line and the FI light lit up while the bike was still running. I pulled into a car park and sat there, but it didn't blink. I shut it off and the light went out. I took the key out and started again, started it up and the light didn't come back on.

So I went and picked up my stuff, long enough for the bike to cool down to about 88C. The bike was running fine again. I still had about 10 mins to ride home, so I watched the temp gauge, when it got to about 100C it started playing up again, but not quite as severely this time and the FI light still wouldn't come back on. I pulled into my driveway and again gave the bike a hard rev, hitting red-line and the light came on again! So I wheeled it into the car spot sat there and watched and this time it started flashing. 1 long flash (this = 10 I understand, please correct me if I am wrong?) and 9 short flashes. So the answer is 42! I mean 19.

The Ignition Pulse Generator according to The Book. Now I'm a little embarrassed to admit this but in my defense, someone told me this is how it works. Last time I saw an error code for this problem, I interpreted it to mean 9 flashes, as you are supposed to exclude the long flash, so I was stumped when I went to replace the IAT sensor and the FI light still said there was something wrong with it!

So, now I will start looking at the Pulse Generator, however I can't find any indication to it in the Service Manual, perhaps someone could point me in the right direction? (I admit I am tired and cranky after work so I didn't have a thorough check.)

And can anyone suggest what I should do to check it/fix it?

Thanks,

I HOPE SO MUCH THAT THIS WILL FIX THE DAMN PROBLEM FINALLY!!!!

[spud786]

Your problem is not heat, bike will go even higher than 95 celcious as a norm

[Guest]

No I know it's not heat per se, but heat is causing something (possibly the Ignition Pulse Generator) to pack it in. Granted, the bike has seen engine temps as hot as 107C before, but normally not in extremely hot weather like it was yesterday. Heat causes expansion, so my first guess would be a faulty electrical connection, especially since the bike works perfectly fine in not so extreme temperature.

So where abouts is the Ignition Pulse Generator and how do I get to it? And once I've got to it, how do I test it?

[Flip]

The pulse generator is bolted inside the clutch cover.

Section 17 of the manual has a test procedure but requires

a peak voltage adaptor, I have never tested one so good luck.

Flip

[spud786]

No I know it's not heat per se, but heat is causing something (possibly the Ignition Pulse Generator) to pack it in. Granted, the bike has seen engine temps as hot as 107C before, but normally not in extremely hot weather like it was yesterday. Heat causes expansion, so my first guess would be a faulty electrical connection, especially since the bike works perfectly fine in not so extreme temperature.

So where abouts is the Ignition Pulse Generator and how do I get to it? And once I've got to it, how do I test it?

Its on the right side of the motor, behind the oil casing some bikes its attached to the stator

should see a connector leading down into the cases

I've done none of this , just looking at the manual

[Guest]

The pulse generator is bolted inside the clutch cover.

Section 17 of the manual has a test procedure but requires

a peak voltage adaptor, I have never tested one so good luck.

Flip

Thanks for that, I'll check it out, might just be some loose wiring. If it's any more complex or involves a peak voltage adapter (which I don't have) I'll get my mechanic to check it when i get the brake pads replaced soon.