[Aced-Up]

My Duc is giving me stammering, spluttering and backfiring issues. I tested the TPS seems ok....but...

I tested the wires for voltage while disconnected from the TPS but when the ignition was ON.

Signal Wire reads 1.85V is this normal? since there is nothing going to the signal wire - unless connected to the TPS (fundamentally).

Images are attached.

Thanks!!

 

[vinnychoff]

I had the same issue as yours with the tps. |The way I tested it is to put the meter on ohms. attach the two pins where you get a reading. Both next to each other. slowly open the throttle or put a screwdriver etc in the tps and turn it slowly. as you turn it there is a point where the tps goes open circuit. this to me indicates the tps is faulty. i would double check with basics. for instance the last time i thought it was the tps. water was filling the spark plug hole and causing it. i have a issue at the moment but again can see water leaking in to the air box.
try that and see what you find out. you should see the readings increase with out any drops. i have put a video on vimeo to show what they look like on the inside.
Vince

 

[Aced-Up]

Thanks for the reply Vince.

I tested the TPS with the connection and it seemed to be ok...no flat spots or jumpy voltage.

The above is the connector which connects to the TPS. I disconnected it, turned on the ignition then multi-metered the signal port. But it is showing a voltage in the signal wire...when disconnected.

Is it normal for a voltage to be in the signal wire port when disconnected from the TPS?

In the meantime, Im going to take the tank off... change the filter and airbox seal... it has age-fatigue cracks on the outside (which could be a possibility). Water, as you said could be a possibility since the issue happened after I washed the bike aggressively a few times.

 

[Tuned]

I've never tried that one… usually you measure the TPS voltage from the ECU side, not the bare wire unplugged from the TPS. On the 748, the ECU connector has a cover that slips off with a single screw and it gives you access to the bare wires. Port 30 is the signal receiving and you can use the battery as ground. With the throttle plate fully closed, (IE unscrew the idle adjuster until the throttle plates are completely closed) you should have 150mv. When fully opened, you should have 5v. Then you set the idle screw so you have 300mv and you're all set. I usually open the TPS very slowly when it's installed and make sure there are no spikes in the signal.

Of course the other way to test the TPS is to use an ohm meter and simply test resistance. However, I've found that to be less accurate when it comes to trouble units.

 

[Aced-Up]

Thanks Tuned - will try that too.

• 
  [*]Is it normal to have 1.85 V in the signal wire when disconnected from the TPS?

If not, I will have to investigate.

 

[Tuned]

• 
  [*]Is it normal to have 1.85 V in the signal wire when disconnected from the TPS?

I can't imagine it being wrong. Sometimes full voltage isn't applied when the circuit is broken. So the 1.85v maybe a bleed, rather then supply, as it should be 5v. The bike would not run without a TPS. So if the voltage was 1.85, the bike would stall the moment you opened up the throttle.

 

[Aced-Up]

I see

Thanks! Just going to have to go through everything one-by-one... there are plenty of ready tips on this forum. Time to get my hands dirty