Wednesday, 3 June 2020

Throttle Control Sensor System on 2003 Triumph Tiger 955i

The issue:  The Tiger stalls occasionally on idle.  Sometimes it seems to hold regular idle around 1000rpm, other times it drops down to 3-400 RPM on the verge of stalling and if I give it gas it cuts out.  It always restarts.

What I've done so far:  replaced the fuel filter and spark plugs.

Next target:  The idle stepper motor:

MOTOR, STEPPER, ISCV T1240888              $123.61
O-RING T3600037                                            $1.37
HOUSING,ISCV,3 CYL T1241064                  $42.79
GROMMET, ISCV T1241063                           $3.84
2000MM                                                            $18.45
145MM LONG                                                  $18.45

$208.51US = $281.34CAD
From Bikebandit's online parts diagrams:

Visual inspection: Gasket (#4 on diagram) is partially squashed, may not be sealing.  One of the pipes was loose going into the back of the unit.

Next step:  remove the gas tank (again) and remove the entire throttle control/idling system, including pipes, and inspect for breaks.  Replace pipes if damaged.  If no pipe damage evident, look into getting a new stepper motor from Inglis Cycle.

Other Possible issues:
throttle slides were out of balance?

After you get the tank off, you need to remove the airbox. This is easy, remove the two bolts on the back of the box and lift it off. You will need to disconnect the breather hose (bottom rear right), electrical connector (bottom front right) and pressure hose to the computer (right middle).

After you get the airbox off, you will see the air idle hoses and valve. Unbolt the valve from its mount and move it out of the way, and disconnect the hoses. Connect the hoses from your gauges (I used a Motion Pro mercury gauge) to the ports and start the bike. You will have to hold the throttle slightly open to keep it running, but it will start with all those wires disconnected. Kinda makes you wonder if you need 'em in the first place!

To sync the throttles, remember that the #1 cylinder (left side) is non-adjustable. Sync the #2 throttle to #1 by adjusting the screw between these cylinders. Once those match, sync #3 to #1 with the other adjusting screw. You might have to repeat the process a couple of times and don't forget to blip the throttle between adjustments to let the linkage settle.

Once the gauges are matched, put it back together, you're done! Check carefully that all the connectors are married up as the tank is a bit of a PITA to pull off again. My EFI light came on for a few starts probably due to readings out of range from the disconnected sensors, but it will reset itself.


I had the CO level reset. I was at .9 and that's very low. They reset to around 2.1.
The stoichiometric ratio for gasoline is 14.7:1. This ratio is when both air and fuel are completely consumed.