At my wits end need help

[bakininthesun]

I have a 2007 m8 That backfires all the time at high rpm. I have changed the stater and pick up coils,I have went over every inch of wiring, I have changed out the throttle bodies,tps and injectors. I have also disconnected the tss and the oil sensor thinking that the ecu went in to limp mode, there are no codes flashing on the dash. The sled runs great at low to med rpm but when you go to full throttle it starts to back fire until you let off the throttle and return to half throttle which led me to believe it was in limp mode. I live at 5000 feet and ride at 7 to 10,000 feet and it does the same thing no matter where I am at. I don't know if I could have a fuel pressure problem and haven't checked that yet but it seemed more electrical, There is plenty of fuel returning to the tank when running. I am running 88 non ethanol and amsoil. Plugs do not look lean at this point. I have disconnected the wiring to the hood and get the same thing. Now I am lost. Thanks for the help in advance.

 

[Hardass]

what are you calling hi rpm ? what rpm does it start doing this

 

[bakininthesun]

Starts at about 7000

 

[bakininthesun]

I also changed the reeds thinking it had broken parts

 

[Sledbrain2]

Once I was riding in CO after 2 days of over the hood powder, sled never thawed out, on the 3rd day I tried to climb a power line and it would back fire at wot, eventually it went away, water in spark plug wires, it could be that just cutting and re-screwing the caps might solve issue, the other could be a voltage regulator that has in the past cause spark issues.

 

[bakininthesun]

I will sure look at those options but it couldn't be that easy could it. LOL The sled sits in a heated shop so it gets plenty of time thaw out.

 

[tchriste]

worn sparkplug wires will do this. look and see if they are rubbing against each other.

 

[Hardass]

Water in the pluggs to the ecu will also do this When it starts missing does it do it steady or does it come out of it

 

[boondocker97]

Powervalves opening properly all the way?

 

[bakininthesun]

Thank to every one I have tried all of your suggestions but still the same. Its making me crazy.

 

[Phizzer]

Did you check the tail light wiring?? I'm pretty sure on this year sleds, the wiring harness chaffed on the tunnel back there causing things to go hay wire. One thing to check out if you haven't already.

 

[diggerdown]

Defiantly check the power valves out. They are suppose to open around that 6900 rpm range. Only other thing I can think of would be a loose part in the exhaust that blocks the amount of flow needed at high rpm.

 

[WyoBoy1000]

Crack in pipe or y pipe.

May not be able to see it without really inspecting it. Sucking in cold are and disrupting flow enough to drop rpm.

I would start there. If you are 100% sure its not a crack, silicone the exhaust donuts and make sure all springs are tights and absolutely no leaks anywhere.

Make sure the can isn't falling apart as well.

 

[Sledbrain2]

There is a rpm sensor at the flywheel that went bad on 06 M7 that gave me similar running issue. I thought it was a tps. Just remember that.