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Discussion Starter · #1 · (Edited)
UPDATE

It will start sometimes and run correctly but after about a minute or so it will fire the cylinders at half the rate. at idle each cylinder is at 600 or so instead of 1200. It is like it is alternating between the two cylinders. There is no fault code and the engine light doesn't come on.

OLD STUFF:
Just put a rebuilt engine in my 2012 800R... Sometimes it starts and runs on both cylinders and runs fine, except seems sluggish at lower rpms. then when i start it again, only the front cylinder will run. Even if I rev it up, the rear cylinder will not start running. I can turn it off and try to start it again and both cylinder may or may not run.... Sometimes both, sometimes only the front cylinder. I pulled the spark plug wire on the rear cylinder when it wasn't running and got shocked.

Usually if it starts on 2 cylinders it will keep running fine.

Has anyone else had a problem like this? The check engine light doesn't come on.

Tried this stuff:
Checked spark plug, good
Checked spark, good
cleaned rear cylinder injector,
swapped injectors (front and back)
checked rear cylinder compression, 180psi
replaced plug cap
new fuel pump filter

Any help would be greatly appreciated.

I will keep this post updated until the issue is resolved. Hopefully I can post a solution.

One other thing. Is it normal to sounds like air leaking when you turn off the engine. Mine does it for a few seconds.
 

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Air leak is probably a vacuum leak. As for intermittent cylinder you got a short either on harness to coil or coil itself is bad or the plug wire on cylinder two.

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Discussion Starter · #3 ·
Air leak is probably a vacuum leak. As for intermittent cylinder you got a short either on harness to coil or coil itself is bad or the plug wire on cylinder two.

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Thanks, wasn't sure if that air leak sound was normal. going to try a timing light on cylinder 2 to see if it is sparking or not.
 

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If you haven't replaced the spark plugs do so. You can't look at them like the old day and see that they are fouled out. And it's possible to buy bad plugs. Several have had that issue.

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Discussion Starter · #5 ·
If you haven't replaced the spark plugs do so. You can't look at them like the old day and see that they are fouled out. And it's possible to buy bad plugs. Several have had that issue.

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ordered some new spark plugs, they are on the way. going to track down that vacuum leak too. thanks for the help.
 

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Discussion Starter · #6 ·
It gets weirder.

1) I fixed the vacuum leak.
2) swapped spark plugs, no difference.
3) put on a timing light and cylinder 2 is getting power, light flashes.
4) used a stethoscope to check if the injector was working. I could unplug it and it would stop tapping, plug it in and taps again.
5) Also check that the fuel line to cylinder 2 was not plugged.

it appears to be getting gas and spark, has good compression. is it firing at the wrong time sometimes?

It will start with both cinders, next time only the front and randomly start one or two cylinders.
I can't figure out what changes between starts. Why one time it works and another it doesn't.
 

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Check the plug on the ecm several have had the pins corrode and turn green.

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Discussion Starter · #9 ·
Check the plug on the ecm several have had the pins corrode and turn green.

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OK, will definitely do that, thanks.. I also ordered a new coil. I found in another forum someone had a similar issue and it was the coil. Spark plug was sparking but not enough. Which is back to where you pointing me... problem with the spark.
 

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Discussion Starter · #10 ·
Swapped coils and also used a coil tester. The old coil was OK. swapping coils didn't change anything.

I did notice if I let it power off completely it will usually start and run both cylinders. If I turn it off and on before completely powering down it will only fire up the front cylinder.

I cleaned both plugs to the ECM, they looked pretty clean. Still no go.

I ordered a used ECM. That's about the only thing left i can think of. I will post an update as soon as I get it tested with the new ECM.
 

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Discussion Starter · #13 ·
I also swapped out the ECM... still only 1 cylinder sometimes. Is it possible it is the valves are too tight? I am going to check that next. Fingers crossed.
 

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Discussion Starter · #14 · (Edited)
I put a tachometer on cylinder 2.. when it is running it fires 1200 time at idle.. but when it runs like crap it is firing around 600.

Any idea what would cause a sparkplug to fire at half its normal rate?

I changed these parts already:
ECM, Key and speedometer
Coil
Spark Plug Cap
spark plug
crank position sensor
Fuel Pressure is 51psi
 

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I'm at a loss first time I have heard of this issue. You have already changed everything I would gave done .

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Have you replaced the plug wire for cylinder 2 ? I noticed you said plug, boot, and coil. If you put an inductive tach on that wire, and read 600 pulses, I would think it has to be ignition related (vs an injector or valve). Have you checked the engine ground? If it's a rebuilt motor, someone's had it apart. You might also pull the crank position sensor, and peer in while slowly turning the crank. See if you might have a bent tooth on the trigger wheel.
 

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Discussion Starter · #19 ·
Have you replaced the plug wire for cylinder 2 ? I noticed you said plug, boot, and coil. If you put an inductive tach on that wire, and read 600 pulses, I would think it has to be ignition related (vs an injector or valve). Have you checked the engine ground? If it's a rebuilt motor, someone's had it apart. You might also pull the crank position sensor, and peer in while slowly turning the crank. See if you might have a bent tooth on the trigger wheel.
I haven't changed the plug wire... that will certainly be next.

I checked the valves and they are good. I also check for fault codes and there aren't any.

I think I made a mistake on what is happening..... going to check to see if both cylinders are firing at 600, every other cycle. Is that what limp mode does? I couldn't find any info on what limp mode actual does. so it is possible both cylinders are firing at 600 and unplugging cylinder doesn't do anything to the idle speed. I am going to test that theory later today for sure.

Someone in another post said they had an issue where the clutch was making a knocking noise and the engine detected it as engine knocking and it caused misfires. My clutch is noisy as hell. So i will be adding washers to make it quiet and try running it without a clutch to see if that helps anything.

Now if it starts running well, after about 1 minute or so it starts running like crap again. and cylinder 2 only fires at 600.

I also used dielectric grease on both plugs and connections to the coil.

I will double check the ground, clean it up. It is firmly attached but could be dirty.

Thanks for the insight. hope one of these things fixes it.
 

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I don't know how the engine can detect knocking.....but I don't know everything. You said fuel pressure was good, but how long did you monitor it? Was it missing at 51psi? FWIW, dielectric grease does not insure a good connection. It is non-conductive. It's function is to seal/protect the metal connector components from moisture intrusion, oxidation, corrosion. Limp mode shouldn't make it misfire, just limit rpm/speed. If it runs good for a minute, then poor, I'd wonder is it starting to starve for fuel? Or injecting too much, starting to foul a plug? Spark check on both cylinders again will tell you something.
 
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