Throttle Position Sensor diagnostics inconsistencies

[raven09]

I'm experiencing poor low speed performance on my '09 with 13K miles, with roughness/stumbling/surging between 1.5K to 4K rpms. I've replaced the plugs, snipped the plug wires, checked the resistance of the plug caps, checked the secondary resistance on the coils, successfully ran the coils, injectors, and PAIR valve solenoid diagnostics, ran a bottle of Seafoam, did a TBS, all without improvement. I had this issue to a lower degree since buying the bike new. When I check the d:01 TPS diagnostic, I always get a different reading on full closed throttle. I've seen the display value jump anywhere between 17 to 21, at various engine temperatures.

I was wondering if this is a sign of a defective TPS or it's just normal behavior at full closed throttle. The d:01 diagnostic display values do increase smoothly all the way to 103 when twisting the throttle. Does the TPS angle just needs to be adjusted? I haven't checked the resistance of the TPS per the FSM instructions, nor experimented with the Barbarian jumper mod and CO values yet. The bike is still under warranty but I don't like to bring it in if I can fix it myself. Anyone seen this before?

Thank you in advance.

P.S. - To do the Barbarian jumper mod, does the battery need to be disconnected prior to disconnecting/reconnecting the ECU connector?

 

[worldbound4now]

Do you have the FSM? In the Gen 1 FSM, it gives an appropriate range for the TPS which has a low end of 15-17 and a high end of 97-100.

When you gradually, slowly open up the throttle during the diAG testing, do you get a corresponding climb in sequentially greater numbers?

You also don't mention anything about your fuel. I've personally experienced performance lag by using high octane fuel (but that opens up a whole other can of worms).

 

[raven09]

I have a soft copy of the FSM, which I downloaded sometime ago from here. The diag values are the same for the Gen 2 bike, and they do increment smoothly to 103. I normally run 87 octane fuel, but I've been running 91 octane for the past week with the fuel cleaner. I haven't noticed any substantial difference between the lower or higher octane fuel.

 

[ionbeam]

The output of the TPS should be stable and repeatable.

If you have a volt meter, back probe the connector to the TPS putting the black meter lead on the Black/Blue wire and the red meter lead on the solid Blue wire. Turn the ignition key ON but don't start the engine. You should read 4.75 to 5.00 volts and it should be rock stable. Now rotate the throttle from close to full open while looking at the meter, there should be no variation in the voltage.(1)

Turn the key OFF and take the red probe off the solid blue wire and put it on the Yellow wire, the output of the TPS. Turn the ignition key ON but don't start the engine. You should be reading 0.65 to 0.75 volts, don't sweat 0.01 volts either way.(2)

Rotate the throttle very slowly from full closed to full open. The voltage should go from the base reading steadily up to ~4.7 volts with no fluttering, glitches or irregularities.(3)

Let the throttle close, is the voltage the same as when you first checked it? Open and close the throttle several times and observe if the voltage on the Yellow wire always is the same when the throttle is closed and open.(4)

=========================

(1) If the voltage is not stable this problem needs to go back to your dealer as a warranty fix, it's probably an ECU or harness problem. No need to go farther. This is a reference voltage supplied by the ECU to all the sensors. If it is wrong at the TPS it will be wrong for all the other sensors too making them all slightly out of range.

(2) This is the voltage you should see. The ECU will do the math and convert it to the 15-17 you should see in diAG:01The ECU display of 15-17 means that the ECU thinks the throttle is 15% to 17% open, the amount set by the idle screw to allow enough air for the engine to idle. If this is the only problem you see the TPS can be adjusted by loosening the two mounting screws (security torx screws) and rotating the body of the TPS per the FSM. The span between the bottom reading and the top reading is fixed, if the bottom reading is high then the top reading should be high too. If the bottom reading is low the top reading should be low. By adjusting the TPS at the bottom reading it will automatically change the top reading by the same amount.(A)

(3) This is the voltage you should see. The ECU will do the math and convert it to 97 - 100 you should see in diAG:01The ECU display of 97-100 means that the ECU thinks the throttle is 97% to 100% open. If the voltage climb is anything but a stable linear climb the TPS is suspect.

(4) If the start voltage and/or the stop voltage is not repeatable within 0.05 volts the TPS is suspect.

If the TPS passes all these tests but diAG still shows the variations you saw the problem is probably in the harness or connectors.

(A) Gen I only: The TPS shaft is locked to the throttlebody shaft, any adjustment to the idle speed will also affect the TPS. If your FJR came from the factory with the idle speed set to 800 rpm, the TPS will be adjusted to 0.675 volts at this throttle shaft physical location. If you then turn up the idle speed using the idle adjust screw it will rotate the throttlebody shaft and because it is mechanically locked to the TPS, the TPS voltage will climb also. If the TPS was set to 0.675 at 800 rpm and you turned your idle speed up to 1,100 rpm the voltage on the TPS will be forced to increase also. This may explain why your diAG reading is too high.

 

[raven09]

Alan,

Thank you for taking the time to write the detailed TPS voltage troubleshooting procedure. I will try to do go through it later today and report back.

Also, in regards to note (A), yes the idle speed was set low by the factory and I had to increase it quite a bit to avoid stalling. I recall reading somewhere that on the Gen 2 bikes the idle adjusting screw is actually controlling a main air screw and consequently it shouldn't have any direct effect on the throttle body shaft. Please correct me if I'm wrong.

Regards,

Joe

 

[ionbeam]

...Also, in regards to note (A), yes the idle speed was set low by the factory and I had to increase it quite a bit to avoid stalling. I recall reading somewhere that on the Gen 2 bikes the idle adjusting screw is actually controlling a main air screw and consequently it shouldn't have any direct effect on the throttle body shaft. Please correct me if I'm wrong.

You are right, I'm just sooooo Gen I. :lol: (A) edited to specify Gen I only.