Cylinder Misfiring

[Richouse]

I cranked the feej up, let it idle a few minutes while I put my helmet on then pulled out of the garage. Everything running smooth at this point. Got the the end of the road and I notice the rpm fall to about 500 rpm and it was about to die if I didn't give some gas. Then I noticed it running like CRAP, one of the cylinders completely quit firing. It had a very noticeable miss even when I goosed it up to 3K to 4k rpm. It even died a couple of times when it came back down to idle. It fired back up but still had the miss. I limped it back home and as soon and I got in the garage the rps jumped up to 1000rpm idle and smoothed right out goosed it a few more times and it ran as smooth as always. I decided to take the chance and ride it to work to see if it would do it again and it did NOT.

Im guessing it lost spark some how to just that cylinder (don't know which one) because it would have completely died if it lost fuel. Only thing not stock is BJM +5. '07 with just less that 13K miles.

Any ideas on what might make this happen???

 

[Hit the Road Jack]

Bad gas, or moisture in your tank?

 

[slapnpop]

Fuel : Air : Spark

Fuel:

bad gas, clogged filter in fuel pump, clogged injector

Air:

hard to screw up only one cylinder there, but blocked intake passages?

Spark: most likely

Spark plugs (dirty, old, incorrectly gapped, broken)

Spark plug wires (bad wires, or short to ground somewhere. Check for oil lead in the spark plug area shorting to ground as well)

Coil

Signal from ECU to Coil

ECU

Crank Position sensor

Throttle position sensor

? cam sensor ?

 

[Wolfhound]

Did you try turning the key off & restarting it ?

 

[Richouse]

Did you try turning the key off & restarting it ?

No, Just pushed the starter button when it died. It eventually cleared up without turning key off.

 

[Duff]

Sounds like what I had at NAFO. It cost me $120 but a dealer pulled about 1/4 to 1/2 cup of water out of my fuel system. About a tablespoon out of the fuel rail alone. Mechanic said the water is more dense and will not go through the injector. It can literally "bounce" on the top of the injector and starve a cylinder of fuel. That is axactly what appears to have happened. After the cleaning, the bike ran like a champ.

Is this your problem? I don't know, but it could be. :glare:

 

[Wolfhound]

No problem before stopping. I've had mine clear up several times just from turning off & restarting . . . .But may not be the same problem, but sounds like it.....

 

[bergs]

Add another vote for moisture.

Maybe a small amount of dry gas to see what happens.

If the bike sat for any amount of time without a full tank, and if the right conditions permit, condensation could very well have formed and collected somewhere in the system.

 

[FJRMaineiac]

I like the spark and water theories. They seem pretty plausible.

Another thought - vacuum. I just had mine serviced for a similar reason. My #4 cylinder wasn't firing at idle (it seemed better at revs above 2000, but still wasn't "right"). The tech didn't show me exactly where it was, but he explained that there is an actuator on or near the fuel rail that adjusts the vacuum and the one for that cylinder was stuck. He said the service manual doesn't even refer to a maintenance procedure for it, but he freed it up and lubricated it (and the others at the same time). We also changed spark plugs for good measure. They were all pretty light colored, indicating it was prolly running too lean anyway. It runs smooth as butta now. I noticed when it was running like crap that it also seemed to be throwing a lot more heat onto my legs, which would seem to corroborate the lean condition. The tech did check the compression on all the cylinders and they looked good, so I don't think any permanent damage was done.

However, (and I have been meaning to post this question for a couple of days now), even though the bike is running subjectively cooler now - it feels cooler on the legs, I am finding that the temp gauge is creeping up to 3 bars a lot more frequently than it used to. Has anyone else experienced this after a TBS? I am wondering if the temperature is really different, or if the sensor got moved slightly during the service. I know the temp gauge on the dash is only slightly better than idiot lights, but I never used to get more than 2 bars when riding, even at around town speeds. Now, if I am driving slowly enough (say 35 mph or lower) and/or am trailing another vehicle for a mile or two, the temp gauge gets up to 3 bars.

Thoughts?

 

[Geezer]

Well, if you are using the gasoline that has 'up tp 10%' alcohol in it then the alcohol should absorb any moisture in the tank that would accumulate from normal condensation. So, my guess is that you got a bad batch of gas that either had a lot of water in it or some other spooge. Rather than ordinary dry gas I would try something that also cleans the fuel system.

 

[radman]

Bad fuel would/should be evident immediately after filling, and persistent, not clearing up after a few minutes. You have 13k, changed plugs yet? Plug wires tight in the caps? Was the bike just washed, or ridden in rain before this episode? Sure it was just one hole missing?

 

[mattster31]

water in your gas maybe??

I had a similar thing happen before. Washed the bike then went for gas......as I opened the cap I saw all the water under the cap flow into the tank. UGGHHH!!! Turns out the overflow outlet was clogged with dirt. Anyways, after the fill up the bike ran like crap for a few minutes while I ran the water through the motor. It cleared up......just a thought.

 

[Zorlac]

"Mechanic said the water is more dense and will not go through the injector. It can literally "bounce" on the top of the injector and starve a cylinder of fuel."

"after the fill up the bike ran like crap for a few minutes while I ran the water through the motor. It cleared up."

Hmmm, now I'm puzzled? :dribble:

 

[Fred W]

"Mechanic said the water is more dense and will not go through the injector. It can literally "bounce" on the top of the injector and starve a cylinder of fuel."
"after the fill up the bike ran like crap for a few minutes while I ran the water through the motor. It cleared up."

Hmmm, now I'm puzzled? :dribble:

Water is more dense, but that doesn't explain why t would not go through an injector. I would think the fuel rail pressure would be high enough to push the water through.

However, how would water effect only one cylinder?

 

[Geezer]

On the Gen 2 bikes, where the fuel does not circulate back to the tank from the fuel rail, I can envision some water getting pushed into the end of the rail and causing a problem on the cylinder at that end. On the Gen 1 the fuel circulates back to the tank, and the alcohol in the fuel will eventually absorb the water and it will be burned along with the gasoline.

 

[Wolfhound]

How does moisture only affect one cylinder ? Sounds like the turning key off & back on fixed it ? No more problems ?

 

[S76]

On the Gen 2 bikes, where the fuel does not circulate back to the tank from the fuel rail, I can envision some water getting pushed into the end of the rail and causing a problem on the cylinder at that end. On the Gen 1 the fuel circulates back to the tank, and the alcohol in the fuel will eventually absorb the water and it will be burned along with the gasoline.

+1 That is what I had in mind.

As far as the water not going through the injector I can't buy that. The fact that it cleared up (assuming it was water which it most likely was) disproves that. Although, another possibility is rather than water it could have been some alchohol not mixed well or just bad gas.

I had this happen twice last summer when down south. Didn't loose a cyl but it ran ragged a few times and cleared up later on. Gas is crap these days.