MCXMTX
Newbie
I have a 2015 Viper MTX SE 153" with the MCX190 turbo. ~3400miles.
Last year the sled ran perfectly fine, reliable, pulled strong, changed the battery to an AGM with a bit more CCA, since the original battery started to crank a little slow.
When I went for this seasons first ride it started up just fine but then it would die from idling. Strange. Old gas? Anyhow:
I rode it for maybe 30 minutes after that and couldn't get it to reverse! It would not hold idle without throttle. With a few choice words I pulled it into the garage to let it thaw and after that the sled would not start! After a good while and with maybe 10% throttle it started but I had to baby it to keep it running.. So I siphoned the old-ish gas out of it and poured in some fresh "premium" gas and changed the spark plugs which were very black. Started just fine and held idle after that so off I went for a short 10-15 minute ride to get it hot and all the fluids pumping. It still pulled strong but would hesitate when jabbing the throttle for a few microseconds, idled just fine. So I went home and the idling issues returned... So with the same choice of words I pulled the sled in to the garage and myself to the computer to look for known issues and here I am. Great forum!
To make a long story short I found out about the finicky throttle cable and adjusted mine according to the credit-card-between-base-and-divet-before-TORS-switch-clicks-spec (mine was slack) with no difference, so I poured in a few drops of oil in between the cable and the housing and it operates a little bit easier now. I checked the throttle cable routing and it is long and smooth. I found out how to get into the diagnostic mode on the screen and could see the TPS output - which at first was fine: 0% (off throttle) and like 96-99% WOT. So none the wiser I tried it again to see if I missed something. This time I got 4% off throttle and 99% 3,9V WOT. A third time I could see it creep from 2% up to 26% without me touching anything - 99-127(?)% 4.1V WOT. A fourth time it was perfectly fine.. Intermittent TPS readings?
So I looked at the throttle body axle(?) and the cable lever down by the throttle bodies and it moves smoothly between closed and open with distinct thuds on the stops at each extreme. The return spring is strong. The cable is visibly slack when the throttle is closed. Looks mechanically fine.
So I started to look at the TPS sensor. It is in there rock solid with the factory marks still aligned on the housing and the screws. I pulled the plug on it and it was clean inside. I measured 20 ohms on the ground, and maybe 4,8 volts from the ECU, the middle wire showed maybe 3 volts (measured in the disconnected plug from the ECU).
I suspect the sled sees an open throttle and fuels accordingly while in reality it is in fact closed and thus runs rich and starts difficult all from false TPS readings, but the TPS's deltas seem fine. It's as if the starting value varies, has anyone heard of any ECU's supplying too much on the 5v pin? I'm almost out of ideas here..
Any thoughts on this is greatly appreciated. I have "normal" guy tools on hand haha!
/Jonathan
Update 1:
Confirmed good ground throughout the chassis, tried disconnecting the MCX turbo box and also tried my old battery again.
Also tried disconnecting and reconnecting the harness from the ECU, tried wiggling the harness. No dice unfortunately.
Last year the sled ran perfectly fine, reliable, pulled strong, changed the battery to an AGM with a bit more CCA, since the original battery started to crank a little slow.
When I went for this seasons first ride it started up just fine but then it would die from idling. Strange. Old gas? Anyhow:
I rode it for maybe 30 minutes after that and couldn't get it to reverse! It would not hold idle without throttle. With a few choice words I pulled it into the garage to let it thaw and after that the sled would not start! After a good while and with maybe 10% throttle it started but I had to baby it to keep it running.. So I siphoned the old-ish gas out of it and poured in some fresh "premium" gas and changed the spark plugs which were very black. Started just fine and held idle after that so off I went for a short 10-15 minute ride to get it hot and all the fluids pumping. It still pulled strong but would hesitate when jabbing the throttle for a few microseconds, idled just fine. So I went home and the idling issues returned... So with the same choice of words I pulled the sled in to the garage and myself to the computer to look for known issues and here I am. Great forum!
To make a long story short I found out about the finicky throttle cable and adjusted mine according to the credit-card-between-base-and-divet-before-TORS-switch-clicks-spec (mine was slack) with no difference, so I poured in a few drops of oil in between the cable and the housing and it operates a little bit easier now. I checked the throttle cable routing and it is long and smooth. I found out how to get into the diagnostic mode on the screen and could see the TPS output - which at first was fine: 0% (off throttle) and like 96-99% WOT. So none the wiser I tried it again to see if I missed something. This time I got 4% off throttle and 99% 3,9V WOT. A third time I could see it creep from 2% up to 26% without me touching anything - 99-127(?)% 4.1V WOT. A fourth time it was perfectly fine.. Intermittent TPS readings?
So I looked at the throttle body axle(?) and the cable lever down by the throttle bodies and it moves smoothly between closed and open with distinct thuds on the stops at each extreme. The return spring is strong. The cable is visibly slack when the throttle is closed. Looks mechanically fine.
So I started to look at the TPS sensor. It is in there rock solid with the factory marks still aligned on the housing and the screws. I pulled the plug on it and it was clean inside. I measured 20 ohms on the ground, and maybe 4,8 volts from the ECU, the middle wire showed maybe 3 volts (measured in the disconnected plug from the ECU).
I suspect the sled sees an open throttle and fuels accordingly while in reality it is in fact closed and thus runs rich and starts difficult all from false TPS readings, but the TPS's deltas seem fine. It's as if the starting value varies, has anyone heard of any ECU's supplying too much on the 5v pin? I'm almost out of ideas here..
Any thoughts on this is greatly appreciated. I have "normal" guy tools on hand haha!
/Jonathan
Update 1:
Confirmed good ground throughout the chassis, tried disconnecting the MCX turbo box and also tried my old battery again.
Also tried disconnecting and reconnecting the harness from the ECU, tried wiggling the harness. No dice unfortunately.
Last edited:
MCXMTX
Newbie
Update 2:
Decided to check the continuity in the TPS wires, so I unplugged the TPS plug and the fuel injection harness plug and measured between those two plugs. I have good continuity on all three wires.
BUT! I also have a strange one way (?) ~1300 consistent ohms readout between the black and blue TPS wire (with the harness still unplugged from the main harness). If I change the prongs on the ohm meter I get nothing.. Change back and I have the same ~1300 ohms. Strange indeed. The readout is very consistent when I wiggle the plugs and massage the harness in place.
On the Arctic Cat "wiring diagram" I see no diodes or resistors or anything of the sort in the fuel injection harness. I suspect I have a strange short in the harness somehow. Not somewhere obvious either....
I'm gonna confirm the measurement with a different meter before I pull the fuel injection harness for further inspection on the healing bench.
Decided to check the continuity in the TPS wires, so I unplugged the TPS plug and the fuel injection harness plug and measured between those two plugs. I have good continuity on all three wires.
BUT! I also have a strange one way (?) ~1300 consistent ohms readout between the black and blue TPS wire (with the harness still unplugged from the main harness). If I change the prongs on the ohm meter I get nothing.. Change back and I have the same ~1300 ohms. Strange indeed. The readout is very consistent when I wiggle the plugs and massage the harness in place.
On the Arctic Cat "wiring diagram" I see no diodes or resistors or anything of the sort in the fuel injection harness. I suspect I have a strange short in the harness somehow. Not somewhere obvious either....
I'm gonna confirm the measurement with a different meter before I pull the fuel injection harness for further inspection on the healing bench.
MCXMTX
Newbie
Update 3 (final):
Turns out my TPS sensors base resistance had gone bad.
I ordered a new off brand one that looks identical and adjusted it using the sleds diagnosis screen. I adjusted it so that it reports 0% with throttle relaxed but not too far because then the sled reports 127% at WOT.
I recommend cycling the throttle from relaxed to fully open while adjusting to get the correct readouts. I'd say 0,6-0,7V relaxed and 3-8-4.0V at WOT. Finicky!
Turns out my TPS sensors base resistance had gone bad.
I ordered a new off brand one that looks identical and adjusted it using the sleds diagnosis screen. I adjusted it so that it reports 0% with throttle relaxed but not too far because then the sled reports 127% at WOT.
I recommend cycling the throttle from relaxed to fully open while adjusting to get the correct readouts. I'd say 0,6-0,7V relaxed and 3-8-4.0V at WOT. Finicky!
HYB90RID
Veteran
- Joined
- Jan 16, 2007
- Messages
- 39
Having same issue this year, but mine seems to be worse than yours, changed out the throttle cable as it had a kink, replaced the TPS with a used good one I had from a Nytro. Kept having random issues sled wouldn't start outside in the cold etc.
Spoke with with DynoJet as I am running a PCV which we happened to find some burnt wires and this was his suggestion
Run an additional ground wire from the battery ground and tap it into the black wire with white tracer in the Power Commander TPS harness. Once this is done, the reading should stabilize and you can recalibrate the TPS again.
Since doing this the sled has been starting in the cold no problem and seems to be running good so far.
Spoke with with DynoJet as I am running a PCV which we happened to find some burnt wires and this was his suggestion
Run an additional ground wire from the battery ground and tap it into the black wire with white tracer in the Power Commander TPS harness. Once this is done, the reading should stabilize and you can recalibrate the TPS again.
Since doing this the sled has been starting in the cold no problem and seems to be running good so far.
