M7 dropping cylinder

[rigrat]

Good day. Hit a tree last season with my m7 which caused damage to my sleds hood, nose piece and other plastic plus the airbox was smashed.When the accident happened i was able to remove loose pieces and ride sled back to my pickup. The problem is that the sled started dropping a cylinder part of the time (may have inhaled some pine needles) into motor. I replaced all broken pieces and cleaned everything up. Took it for a rip down the ditch yesterday and found it would still drop a cylinder. Sled seems to run ok at idle and part throttle but when opening it up to full throttle it will drop a cylinder everytime. If i go back to part throttle it will run on both cylinders again. Checked the compression and found both cylinders were within 5 lbs. One plug looked like it may have been fouling so i replaced it. No difference. If it was ignition it would probably run on one cylinder all the time, correct? Could it have a broken reed and would a broken reed cause it to act this way? Appreciate any and all help! Thanks in advance.

 

[snowzombie]

Failed reeds wont cause that condition, it would be more likely to be backfiring through the intake and they are not usually damaged by impact. When you say it drops a cylinder are you sure its not going into limp mode? Have you checked the ECU for codes? if I had to guess from what you described for damage you could have a problem in the wiring harness as it would have been located in the area you damaged. I know another guy with an M-7 who had a similar problem after melting the harness from installing twin pipes.

 

[rigrat]

So how do i check ecu for codes?

 

[rigrat]

Dealership mentioned unhooking kill switch. Tried it and made no difference. I will pull the plugs again to see if the new plug is starting to foul. Wiring harness looks ok.

 

[woodies]

should be a decal underhood either on air box area or belt gaurd with the codes on it unless they changed it will be flashing lite in guage.

 

[rigrat]

No flashing lights. Thanks.

 

[rigrat]

Pulled plugs again. Muffler side spark plug is damp compared to clutch side plug. Checked spark with plugs pulled and there is lots of spark. Wiring harness and connections all look good. Did a compression test again while i had the plugs out and both cylinders were within 1 lb (115).

 

[snowzombie]

when you replaced the airbox did you reinstall the sensor? could cause a poor runnng condition if its not installed or was damaged in the crash. if spark and compresion is good you may want to check the fuel pressure.

 

[rigrat]

Going to check fuel pressure. Sensor looked good and the sensor side of the old air box was not damaged but i will pull sensor and take a look at it again. Any chance that an injector could be acting up? Just seems kind of funny that the muffler side plug is damp and the other plug looks fine.

 

[snowzombie]

could be a sticky injector i guess, a bit of work but a simple way to diagnose would be to pull the rail and swap the injectors side to side and see if the side that looks like its overfueling changes with the injector. it doesnt sound like an injector though the way you described it running fine until you go to full throttle. have you checked the ground connections as well very important on the efi system running properly. if it hasnt ran the same since the impact one would expect something got jarred loose that is causing your greif, thats why i would think electrical.

 

[rigrat]

I appreciate the help. I will post what the problem was once i get it figured it out. Thanks again.

 

[swabby]

have you checked the power valve servo maybee a cable poped off ive seen that a few times and that will happen if they are dirty seen it on a m7 rental and my 05 m6

 

[rigrat]

OK, i pulled injection off and checked reeds. Found a piece of the broken air box laying in the reed cage. Removed it hoping it would cure the problem, no go. I have yet to check the fuel pressure. Seems like if i go from an idle to full throttle it will drop the cylinder everytime. If i am at part throttle and slowly go to WOT it will run ok part of the time. I did another visual check of the sensor in the air box and it looked ok. Another thing i noticed is that the air box side of the injector bodies seemed fairly oily, is this normal?

 

[swabby]

have you checked the power valve servo and see if a cable is off or damaged and function the cables manualy to ensure they are working correctly , it realy sounds like it could be as simple as that ,especialy if it runs good at low rpm. i have seen this b4 a few times

 

[rigrat]

Checked powervalve servo, all looks ok. Cables are good and everything moves freely.

 

[swabby]

im stumped good luck, might halfto bite the bullit and haulit up to lethbridge cat or somethin

 

[Summiteer]

sounds electrical, do cats have throttle position sensors?

 

[swabby]

yes they do have a tps sensor , that could be it

 

[rigrat]

So how do i check the tps?? Thanks.

 

[Haggis]

I had v force reeds on a sled that one of the petals broke - caused that condition you are describing exactly. Did you go through reed cage thoroughly???