Did i blow my top end, or are my power valves not working right?

[AKpow]

M8 will not get above 7300 RPMS. Runs really rough, spitting and sputtering right around when the power valves are supposed to open, between 6500 and 7. above 7000 RPMs forget it. Runs fine bleow 6000 RPMs. Started doing it toward the end of the day. Got stuck and pinned the flapper to and almost got out. Next time up the hill it ran like crap.

Any thoughts?

 

[bigcat_ak]

Think you have it pegged.Power valve problem.

 

[JHG]

Is it giving you any codes? The powervalves will attempt to open three times then quit. It will give you a code if they fail to open. I was chasing what I thought was a powervalve problem that turned out to be something totally different. If a exhaust temp sensor, intake air sensor, knock sensor or coolant sensor goes out it will go into limp mode and lose top end. The fact that you're getting into the 7000+ range makes me think it's not the valves. On the M8 the PV's have three positions, closed, mid and open. They go to mid at 6300 RPM and full open at around 7800 RPM. If it is the valves and it bogs then pulls RPM they may just be dirty and it's taking a couple cycles of the servo to get them open. Good luck, problems like this suck.

 

[AKpow]

The check engine light came on, but not long enough for me to get a read. and it wasn not the wrench light, it was the actual check engine light. I tried to get it to come on again doin a few longer pulls but no dice. when i got it home i put it up on the stand and tried to get the light to come on again but it wouldn't nor would it go above 7200 RPMs. Thanks for the replies. Thinkin i may just bite the bullet and take it to the shop if its not the power valves.

 

[AKpow]

Is it giving you any codes? The powervalves will attempt to open three times then quit. It will give you a code if they fail to open. I was chasing what I thought was a powervalve problem that turned out to be something totally different. If a exhaust temp sensor, intake air sensor, knock sensor or coolant sensor goes out it will go into limp mode and lose top end. The fact that you're getting into the 7000+ range makes me think it's not the valves. On the M8 the PV's have three positions, closed, mid and open. They go to mid at 6300 RPM and full open at around 7800 RPM. If it is the valves and it bogs then pulls RPM they may just be dirty and it's taking a couple cycles of the servo to get them open. Good luck, problems like this suck.

I re-read the part about the power valves attempting to open three times then they will throw a code. I will run the sled on the stand again tomorrow and rev it up three or four times consistently and maybe get it to show a code. not sure if i ever did three consistant runs at it.

Thanks

 

[Snowman 2001]

I would suggest a compression test. A compression test will tell if it is something to do with the pistons or rings. Check the plugs and caps while you are at it. A bad plug wire or coil could cause a miss fire at higher rpms. If the compression is good and all four plugs look good then go from there.

Does the engine sound different then it did before?

 

[SaberKitty]

Check the 15A fuse by the CCU. After last year, I now carry spares.

 

[AKpow]

I would suggest a compression test. A compression test will tell if it is something to do with the pistons or rings. Check the plugs and caps while you are at it. A bad plug wire or coil could cause a miss fire at higher rpms. If the compression is good and all four plugs look good then go from there.

Does the engine sound different then it did before?

At 7000 RPMs it starts breakin up bad, sound like a dragster minus all the juice. kinda like a pop pop pop. anything below that RPM range its soudns and runs fine.

I will check sompression. Can i get a compression tester at the Autoports store for this thing?

 

[M6johnny]

At 7000 RPMs it starts breakin up bad, sound like a dragster minus all the juice. kinda like a pop pop pop. anything below that RPM range its soudns and runs fine.

I will check sompression. Can i get a compression tester at the Autoports store for this thing?[/QUOTE]

Yeah, I bought one a few years ago for like 30 bux.

 

[wald]

i was in the big horns this weekend and mine did the same thing as your sled i found the mag side plug wire was pulled halfways out of the boot. fixed it and ran perfect again check that

 

[glassman]

Definately check the spark plug caps. Look for any signs of arking (black soot on the top of the plug). Your power valves will open about 5500 rpm so i doubt it is them as the machine will still run ok, just no power. Next is a compression test as well as check for a broken reed. A reed will make it run rough but not necesarily on the top end only.

 

[fuco]

what year is youre m8

 

[AKpow]

checked the fuse and it was good and the cables still seem to be intact. I detatched them from the servo and pull on them with some pliers and they seemed to be fine. I will check the spark plug caps. the last time i had them off there was some black soot but i figured it was the di-electic grease i put on them the last time i changed plugs.

The sled is a 2007.

What would casue the plugs to arc inside the plug caps, not seated properly?

 

[wald]

the boot that pushes down on your spark plug can be removed from the actual wire make sure the boot is pushed on the wire all the way tread it clockwise as you push it on the wire. you should be able to feel it click when you push it onto the plugg if not look inside to see if the clip is broke or bent to far open.

 

[AKpow]

SO i looked at everything that was mentioned above. Servo works, Exhaust temp sensor checked out, Looked over plugs and plug caps to the coil wire and made sure all was seated well, did a compression test and that was good, i cleaned the valves and replaced the cables, clutch side was really ragged.

So now on the track stand it runs well at top end but it will NOT pull full RPMs, got up to 7400 max. I'm thinkin it wont pull full rpms because the clutches can shift out to fast due to the lack of resistance on the track.

Anyone have insight on this before i start looking into any other problems?

 

[Snowman 2001]

Did you gain RPMs, on the stand, when compared to before you cleaned the valves?

 

[AKpow]

Did you gain RPMs, on the stand, when compared to before you cleaned the valves?

Yes, a few hundred and the motor does not break up real bad like it did before. I have a torsional clutch so I am wondering if that has anything to do with it. Maybe the torsion clutch shifts out too fast because there is no resistance at the track?

 

[glassman]

You should be able to rev out to full rpm. If you need too try taking the belt off just dont over rev. So this started after you pinned her for a few seconds? No engine codes being thrown?

 

[wald]

also on my m7 i couldnt get more than 7600 rpms with 65 gram weights in at 2500' i found that my exhaust can broke apart inside and it was causing a restiction. Check that out

 

[AKpow]

You should be able to rev out to full rpm. If you need too try taking the belt off just dont over rev. So this started after you pinned her for a few seconds? No engine codes being thrown?

OH SNAP, i can only read this thread for two more posts. I had seen the engine light flash but not long enough for me to get a read and I havent been able to get it to come back on since, and this was right when it started to run crappy.

I will check the can. Thanks for all the help.