Question about 2002 Yamaha YZ 426 F
Problem goes away if disconnect the Throttle Position Sensor (TPS). Yamaha did a bench resistance test of TPS and said it was OK. Per the manual, Voltage test of TPS (done connected) and voltage out of CDI (done with TPS disconnected) check within specification.
Yamaha states they have never heard of a TPS going bad. Don't want to buy a $270 part that I can't return.
Should I conclude TPS is bad? Can bike be ridden safely without TPS?
Also, 2 mechanics have gone through the carb and it now has all new jets - this did not fix problem. Valve lash adjustment just completed also. Bike starts on 2nd kick so no starting issues.
As with any electro-mechanical moving part, they have been known to malfunction or ultimately just plain wear out. Besides that, they are often victims of improper service procedures.
These procedures will either result in damage to the sensor, or impair its range of operation. In any event, a malfunctioning, damaged, or misadjusted TPS will cause a variety of driveablility symptoms. The only option is to replace it...
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Posted on Apr 20, 2009
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Posted on Jan 02, 2017
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Throttle Position Sensor
The 3 wire Throttle Position Sensor (TPS) is mounted on the throttle body and is connected to the throttle blade.
The TPS is a 3wire variable resistor that provides the Powertrain Control Module (PCM) with an input signal (voltage) that represents the throttle blade position of the throttle body. The sensor is connected to the throttle blade shaft. As the position of the throttle blade changes, the resistance (output voltage) of the TPS changes.
The PCM supplies approximately 5 volts to the TPS. The TPS output voltage (input signal to the PCM) represents the throttle blade position. The PCM receives an input signal voltage from the TPS. This will vary in an approximate range of from .26 volts at minimum throttle opening (idle), to 4.49 volts at wide-open throttle. Along with inputs from other sensors, the PCM uses the TPS input to determine current engine operating conditions. In response to engine operating conditions, the PCM will adjust fuel injector pulse width and ignition timing.
The PCM needs to identify the actions and position of the throttle blade at all times. This information is needed to assist in performing the following calculations:
Ignition timing advance Fuel injection pulse-width Idle (learned value or minimum TPS) Off-idle (0.06 volt) Wide Open Throttle (WOT) open loop (2.608 volts above learned idle voltage) Deceleration fuel lean out Fuel cutoff during cranking at WOT (2.608 volts above learned idle voltage) A/C WOT cutoff (certain automatic transmissions only)
Removal & Installation
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