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Revisiting TPS continuing problem

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I continue to have intermittent problems while accelerating under boost - engine light and TCS light (sometimes ABS) come on while engine stumbles - codes say throttle position

At rest I can read real time from my Foxwell NT 510 elite the TP sensor (5.718 to 29) AP sensor (0.937 to 81.4) actual AP1 (0.392 to 81.144)

As I depress the throttle the numbers move through the ranges smoothly - except the TP sensor which sticks at 28 at half throttle

I do Not know what the units are - I assume degrees but that would sugest a bad sensor - I have a new one ready to install and the last time I had issues my mechanic installed a used sensor (5 years ago) so changing it out will not be too bad

What do you think about the number ranges? I have Not measured for voltage as I thought the scan tool would be the best place to get readings

Thanks

Rich
 
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The sensor supply bus on the NSX ECU is 5 volts. The raw TPS output voltage on the wiper terminal will vary from something above 0 volts to something less than 5 volts from closed to open (I can't remember whether it is 0 to 5 volts opening or 5 volts to 0 opening). The service manual provides the correct voltage range from closed to open. Before messing with the TPS I would carry out the test procedure as described in the service manual which involves checking the TPS output voltage. You didn't specify the DTC number; but, assuming you are correct, that along with the odd behaviour associated with the scanner reading does point to the TPC. However, make sure because you don't want to go messing with the TPS if it isn't the problem. As I recall, Honda does not consider the TPS a repairable item.

I don't know what your scanner is reading. It is definitely not degrees. Perhaps a percentage of maximum voltage?

As an observation, the TPS is not super critical to engine operation. Its big function is usually to signal to the ECU to provide acceleration enrichment and to tell the ECU when the throttle is closing ( fuel cut) and contribute to the idle control signal.

You didn't specify whether your car is cable throttle or a DBW car. That could change things.
 
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The sensor supply bus on the NSX ECU is 5 volts. The raw TPS output voltage on the wiper terminal will vary from something above 0 volts to something less than 5 volts from closed to open (I can't remember whether it is 0 to 5 volts opening or 5 volts to 0 opening). The service manual provides the correct voltage range from closed to open. Before messing with the TPS I would carry out the test procedure as described in the service manual which involves checking the TPS output voltage. You didn't specify the DTC number; but, assuming you are correct, that along with the odd behaviour associated with the scanner reading does point to the TPC. However, make sure because you don't want to go messing with the TPS if it isn't the problem. As I recall, Honda does not consider the TPS a repairable item.

I don't know what your scanner is reading. It is definitely not degrees. Perhaps a percentage of maximum voltage?

As an observation, the TPS is not super critical to engine operation. Its big function is usually to signal to the ECU to provide acceleration enrichment and to tell the ECU when the throttle is closing ( fuel cut) and contribute to the idle control signal.

You didn't specify whether your car is cable throttle or a DBW car. That could change things.
Thanks for the fast response- I have a 97 and DBW (and turbo charged)- part of me wants to think my issue is my tune- possibly the calibration of the meth injection - under boost in 3rd the car will buck (like sudden fuel cut) and the engine light/TPS etc will light up - car will drive but bucks a little until I clear the codes- I will look at the voltage tomorrow. My tuner (who has closed his shop) changed out my TPS a few years ago when I had a similar problem- he installed an old sensor from a honda accord (rather than change out the whole throttle body)- worked fine until recently.

thanks again

Rich
 
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Ah okay that won't be very helpful with diagnosis.

First step is going to be measuring the voltage swing of the TPS. A properly functioning Honda TPS will read ~0.5v closed and ~4.5v open.
 
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I was having trouble back probing- (and my scan tool provides strange numbers- possibly % of max voltage but that makes no sense - try again this weekend
 
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Which DTCs are you getting? P0122 and P0123 are for the throttle switch and would tell you whether the sensor is stuck reading low or high. P1243 and P1244 can also be caused by the TPS; but, can also be caused by other stuff. Reading with an enabled scan tool should provide the TP senor openings in percentage and the TP should go from 10 - 90 % (closed - open). P1241, 1242, 1246, 1247, and 1248 relate to other parts of the DBW system.

As Motor Mouth describes, the definitive check for the actual TPS is measuring voltage at the TPS as described on page 11-111 of the service manual. It describes measuring the voltage right at the TPS terminals while you push the throttle plate open with your fingers. The voltage should range from 0.3 v (closed) to 4.5 volts (open). If your voltage fails the range test then your sensor has failed - again. If the voltage swing matches factory spec then look elsewhere for your TPS related problems.

Since you indicated that the TCS light is coming on, have you tried deactivating your TCS to see if your 'stumble' is actually caused by operation of the TCS? Also, check for stored codes in the ABS and TCS systems. These systems do not communicate through the OBD-II port so you need to use the service check connector to display any error codes through the blinking dash lights.
 
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