Bad Throttle Position Sensor???

[VagaBondGravy]

alright so my car has been acting up lately and i think the TPS might be screwed and i'm gonna have to replace my throttle body. I did some data logging with my accessport when the car was running and i noticed the TPS Duty was jumping all over the place, whether i was idling, accelerating, or WOT. You can physically feel the car surging as if the throttle body is opening and closing. It also jumps around when the car is off and the key is turned to the ON position.

 

I also checked the TPS Voltage and the Throttle Position and they were exactly what they were supposed to be...

 

TPS Voltage - 0.7V at no throttle and increases to 3.9V at WOT

Throttle Position - 5% at no throttle and 100% at full throttle

 

Let me know what you think

 

..oh and car is a 2008 Spec-B

 

I would reset and clear ECU, then "Re-learn" the DBW(drive by wire) cant remember how to do it off my head but i bet google can tell you how

[alcyonegtb]

Sorry to bring back a dead post, but it’s the most relevant I found.

So, My Baja Turbo would do this no throttle or stalling issue all the time. One time i had removed the throttle body to replaced something, I can’t remember, and reinstalled everything and it would not start. So I was stranded at my work for 2 hrs. Screwing around with anything and everything I touched. Finally it worked after multiple restarts and pulling the throttle body off and on again. That was on the original engine. Fast forward to Monday. Car started acting funny, diving and bucking while on the throttle steady. Then I had nothing while on the highway. Pulled off and the throttle was stick at 3k but on showing 17% pedal. (So no power at 17% bc I remapped my throttle for a more linear feel.) Turn the car off then I’m again and everything works. But it continues to sporadically dive and buck on throttle. The TPS Duty is straight bonkers. Pedal shows normal and TPS voltage shows normal on the AP3. Not sure where the values are checked.

My BMW does the throttle bucking at very light throttle, just like the Baja, and the fix for that seems to be a total system parameters relearn. I did it 1 at a time and it changed when I relearned the MAP sensor. Hrrmmm.

Back to the Baja.

Here’s the long winded kicker. I have had an erratic idle since I put the EJ20Y in. The only things that are the same are the wiring harness, the coolant sensor, the map sensor, and the FPR. And the factory Subaru Air/Fuel sensor is mostly new, roughly only 3,000 miles old. Now it’s possible the the throttle body from the EJ20Y is f***ked. I have tried to relearn the throttle every way possible at least a dozen times and it’s always all over the place, diving from rich to lean. It Definitely seems worse the colder it gets, but it could just be time. I don’t remember it doing the stumbling part last winter, but the idle is the same. So much so, that my tuner gave up on the car stating something mechanical is wrong with it, and that’s why I got a Cobb tuner license and started tuning it myself.

But I’m starting to lean towards the wiring harness. It does make sense, it controls all the data moving to the ECM.

Thoughts?

 

 

Sent from my iPhone using Tapatalk

Edited December 30, 2020 by alcyonegtb

[bob307]

Sorry to bring back a dead post, but it’s the most relevant I found.

So, My Baja Turbo would do this no throttle or stalling issue all the time. One time i had removed the throttle body to replaced something, I can’t remember, and reinstalled everything and it would not start. So I was stranded at my work for 2 hrs. Screwing around with anything and everything I touched. Finally it worked after multiple restarts and pulling the throttle body off and on again. That was on the original engine. Fast forward to Monday. Car started acting funny, diving and bucking while on the throttle steady. Then I had nothing while on the highway. Pulled off and the throttle was stick at 3k but on showing 17% pedal. (So no power at 17% bc I remapped my throttle for a more linear feel.) Turn the car off then I’m again and everything works. But it continues to sporadically dive and buck on throttle. The TPS Duty is straight bonkers. Pedal shows normal and TPS voltage shows normal on the AP3. Not sure where the values are checked.

My BMW does the throttle bucking at very light throttle, just like the Baja, and the fix for that seems to be a total system parameters relearn. I did it 1 at a time and it changed when I relearned the MAP sensor. Hrrmmm.

Back to the Baja.

Here’s the long winded kicker. I have had an erratic idle since I put the EJ20Y in. The only things that are the same are the wiring harness, the coolant sensor, the map sensor, and the FPR. And the factory Subaru Air/Fuel sensor is mostly new, roughly only 3,000 miles old. Now it’s possible the the throttle body from the EJ20Y is f***ked. I have tried to relearn the throttle every way possible at least a dozen times and it’s always all over the place, diving from rich to lean. It Definitely seems worse the colder it gets, but it could just be time. I don’t remember it doing the stumbling part last winter, but the idle is the same. So much so, that my tuner gave up on the car stating something mechanical is wrong with it, and that’s why I got a Cobb tuner license and started tuning it myself.

But I’m starting to lean towards the wiring harness. It does make sense, it controls all the data moving to the ECM.

 

What sort of codes do you pull up?

You mentioned EJ20Y swap, which ECU are you running?

Legacy/Outback owners have reported this, I'm dealing with something similar in my EJ20Y swapped 06 Legacy.

See if this thread helps: https://legacygt.com/forums/showthread.php/p2138-throttle-pedal-position-sensor-switch-150344p8.html?highlight=P2138