08 m8 engine problems. limp mode?

B

bartonls

Free Member

Dec 14, 2010

53

1

8

Colorado

• Jan 28, 2012

• #1

Hey guys,
went riding today and m8 ran horrible for first mile, then great for .5 mile. then horrible again so I shut her down. changed plugs and same thing. all four plugs had spark. it just wont rev up, sounds like fowled plugs but apparently not. Checked servo motor and cables. Unplugged servo motor and thought I plugged it in all the way. Tried starting it and nothing. found out the plug wasn't all the way in so tried it again and nothing. Towed back to trailer. finally got it started and PTO side egt gauge never heated up. seems like it is running on one cylinder (mag side). When it is in limp mode what cylinder keeps running? I do not have a speedometer or gauge to see what codes it is throwing.

engine was built by speedwerx (ported, polished, the works). ECU programmed by arctic cat race team. Oil delete. Has custom twin pipes from speedwerx. Today just so happened that it was the first day I added a gallon of 100LL to a tank of 91 octane.

Thanks for any thoughts and replies!
Landon

 

B

bartonls

Free Member

Dec 14, 2010

53

1

8

Colorado

• Feb 12, 2012

• #2

anyone?

 

A

ACMtnCat

Well-known member

Nov 26, 2007

2,348

1,359

113

Utah

• Feb 12, 2012

• #3

Possible pipe temp sensor failure. You need a stock gauge so you know what's going on. codes!

 

m8magicandmystery

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Lifetime Membership

Jan 20, 2008

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113

Yukon

• Feb 12, 2012

• #4

take your main harness plugs apart and check for moisture.at ecu..steering column etc....replug with some dielectric grease applied...look for possible short on tail light wires...and servo motor wires...check plastic tube from ecu for moisture or blockage

 

m8magicandmystery

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Lifetime Membership

Jan 20, 2008

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Yukon

• Feb 12, 2012

• #5

smart vavles malfunction in tank..??...reed failure ..??..power valve stuck even though cables and motor ok..??..head gasket leak one cylinder..???...lots to check but faily simple to check...just throwing idea;s at ya

 

S

strong

Free Member

Oct 11, 2010

102

59

28

Colorado Springs

• Feb 13, 2012

• #6

Mine did that and it turned out to be the tail light was shorting.

 

B

bartonls

Free Member

Dec 14, 2010

53

1

8

Colorado

• Feb 14, 2012

• #7

thanks guys, the problem is that all the wiring is a mess, I used my brothers gauge but it will only light it up. basically everything that isn't being used has the wires cut (like head lights, tail lights, all that stuff). its a sno pro 600 chassis but with a m8 motor. so no head lights, tail lights, etc. I can't get any code readings unless i buy a whole new m8 wiring harness which is really expensive and then use my brothers gauge. I can't use his wiring harness because his is a turbo and the wiring is different.

I installed a new pipe sensor and same issue. I used his turbo ecu and it allowed it to hit higher rpm but still didn't run quite right but that is probably because the pipes I have on mine and i'm not sure if his ecu is stock.

As far as fuel pump... its a sno pro 500 fuel pump since it is in the sno pro chassis. Sounds sketchy but it worked awesome before so it shouldn't be a problem. I guess I can check the o rings in the head.

 

B

bartonls

Free Member

Dec 14, 2010

53

1

8

Colorado

• Feb 14, 2012

• #8

So all of the running of the sled I have been doing it with the belt and clutch off because the primary is broken.

Power valves open and close if it happens to hit the right rpm. Cables are at 35mm.

If I give it 1/4 throttle it will rev up and everything seems good, power valves open, and it hits high rpm. If it give it over 1/2 throttle or pin it it just bogs down, power valves close, and it just stays at that same rpm. It starts running really rich and blows smoke because it is rich.

I went through all the plugs and applied dielectric grease.

brand new spark plugs.

New pipe sensor.

Could it be any other sensors that would cause this?
Does this sound like it goes into limp mode when I give it full throttle?

Sorry guys I just have no idea

 

B

bartonls

Free Member

Dec 14, 2010

53

1

8

Colorado

• Feb 15, 2012

• #9

what about bad reeds? that could potentially cause it to run rich and bog down at full throttle.

Also could this be a bad crank seal, or would that make it lean instead?

The only other thing besides the ECU being shot would be the TPS. I have pulled this engine out probably 4 times this season already, replacing water pump one time, mechanical seal behind water pump the other, leak in coolant line under the engine, and also a bend lower gusset. Could have bumped the TPS, how can you check this? But that doesn't change the fact that it did run better with the brothers 07 ecu. I really don't want to have to replace that.

Once a ECU is bad, is it just bad or can it be fixed. There is a little moisture in the clear box under the ecu (it reads barometric pressure I believe)

 

B

bartonls

Free Member

Dec 14, 2010

53

1

8

Colorado

• Feb 16, 2012

• #10

just an update

hey guys, used a needle and syringe and filled up that clear box under ecu with rubbing alcohol. then sucked as much out as i could using the syringe. tried it on sled today in the garage and it seemed to have fixed it. I will try it in the mountains this weekend and let you all know what I find out.