Bad Throttle Position Sensor???

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

Any progress? My 05 legacy Gt is doing the same thing.

Figured it out at least for my problem.... Wound up being a bad oxygen sensor that wasn't throwing a CEL. If you want to check this you can unplug the front O2 sensor. If that fixes the problem then try replacing that. $150 for an oxygen sensor is better than $450 for the throttle body. let me know how it goes

My 2005 legacygt TPS sensor was having issues. I could be on the highway (cuise control) and the car would go into limp home mode and throw a CEL. Or, I would be in city traffic, the rpms would surge, eventually throwing a CEL and go into limp home mode. These events only occurred in cold weather months.

 

Solution: I cleaned both the accelerator pedal sensor and throttle body sensor with electrical contact cleaner. I think the brand was CNC, purchased via Homeboy Depot. I then noticed that the TMIC had light oil residue throughout, as well as a small accumulation/puddle in front of the throttle body. So I removed and cleaned the TMIC and Throttle body with throttle body cleaner. Not sure which one of these solved the issue, most likely the sensor contacts being cleaned. But the issue has not returned for a few months now.

 

 

 

Summary:

• Engine rpms surge, check engine light, limp home mode
  
• clean accelator pedal/throttle body sensor contacts with electrical contact cleaner
  
• (if oil residue in TMIC/throttlr body butterfly valve) clean with throttle body cleaner
  

Yep, had exactly the same problem on my 05 LGT, cleaned pedal sensor, throttle body. It would throw a cel and go into limp mode every 50-100 miles, so far drove 1000 miles no problems.

But instead of electrical cleaner i used 4000 grit sandpaper on contacts. Edited December 29, 2012 by volodyalysak
misspeled

Same issues right now, popped off the APP sensor on the peddle over the weekend and blew out with Air and reseated same issues... My next idea is to try to clean/reseat the TPS sensor on the Throttle body... Jeezus I could really use a break right now on this. Car has really been acting up with this nonsense and can't even drive it right now

 

My issue is happening like clock work right now. Drive 3 or so miles OR LESS and it dumps into limp mode.

Keep us posted, curious to see if the throttle body sensor resolves the issue.

 

 

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I'm REALLY not trying to go that route as of yet.... Because that requires full replacement of the Throttle body from what I'm getting told by the dealer and my research, they are built into each other

 

Thinking about trying to replace the pedal APP sensor or assembly first to test my luck.

This issue has been REALLY inconvenient and expensive so far

Yes they are integral and part costs around $700 iirc, suggest trying to clean sensor contacts on the sensor.

 

 

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Yea DEFINITELY going to give that a shot first!

 

Really crossing my fingers smh.... Thank god I Live in AZ now and it doesn't really rain, because I've been riding my Motorcycle to work everyday for the last 3 weeks! I can't even drive the car at all right now, for the fear and fact that it dumps every time like clock work once the codes get thrown

I have a very similar problem, but with the manual trans it jut stalls at red lights. Inconvenient to say the least. I threw a CEL though anf got three codes: the dreaded P0420 code, a system too rich code and a mass air flow code. I had unplugged and cleaned the contacts on thr mass air flow and that seemed to reseolve the problem temporarily. However it started acting up again today so i put a scanner on it and the throttle position was stuck at 14% no matter how I drove. Cycled the key off and then on, and the scanner picked up a reading of 14% at idle and 78% at WOT. Going to try the cleaning of the contacts on the pedal sensor and the TPS on the throttle body and report back...

So cleaning the electrical contacts did nothing, but unplugging the front 02 sensor made a huge difference in drivability and gas mileage. Car is still running in open loop for the time being until I install the new sensor but once I get it and do the drive cycles i will repost and let everyone know what the deal is

Front O2 sensor is bad. Causing STFT to bounce all over giving you the surges and drops in RPM.

This is one of those issues that makes me question fly by wire throttles!

 

Its amazing to me that an O2 sensor can trip such a dramatic change in an engine, even after being a tech for years.

Yup, front 02 sensor was stuck reading .957 volts. Dumping fuel like a mofo. New sensor car is all better

So I put in the new 02 sensor this evening at work and it seems to have sortof resolved the issue. The CEL went away on its own after driving around for a little while but the TPS sensor still wont read anything less than 14% and nothing more than 78%. Yes I did check to make sure my floormat wasnt stuck under the pedal . I cleaned the contacts and that helped how the car runs at idle but I'm leaning toward a bad TPS which would not be cool... Upside is the car now runs and drives. Also now that I'm thinking about it, theres a ground strap that *used* to run from the heatshield on the manifold to the framerail on the passenger side. It is broken... So I'm gonna replace that too and see if I get lucky. Fingers crossed! Edited June 4, 2014 by gt06unlimited

Just want to say thank you to everyone on this tread and legacygt.com that described the same issue I was having with my LGT 2008 automatic. We were going crazy trying to narrow down what the issue could be. A lot of man hours on the trouble shooting were spent with negative results until I search on Google and read this tread. The front oxygen sensor was the culprit and as mentioned here no CEL what so ever. Did unplug the bastard oxygen sensor and went for a ride and the car was running without any issues. Went back to the shop plugged the oxygen sensor back again and the problems were there. A new oxygen sensor was bought and the car is running perfect again.

Thank you guys and http://www.legacygt.com.

Guys, I had this issue every time the weather got cold. People suggested the peddle sensor, so I sprayed the shit out it with electric contact cleaner.

 

That was year and a 1/2 ago. Clean that connection behind the peddle, it worked for me.

Hoping this will resolve my very similar issue! Thanks for the great detail.

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

 

bump...

 

my 07 did this EXACT same thing last weekend when it died. throttle pos was good voltage was too but the duty% was all over the place. from - to +.

 

dealer said stft were very high and i needed a new maf. bought one but i still have idle and off-idle issues.

 

the kicker is i replaced the front 02 around 1000-2000 miles ago as preventative.

 

i did the fuel filter and pump this past weekend for prep for a vf52.

 

will be taking the car to a shop of thursday for throttle testing. the same one that did my front 02.

bump...

 

my 07 did this EXACT same thing last weekend when it died. throttle pos was good voltage was too but the duty% was all over the place. from - to +.

 

dealer said stft were very high and i needed a new maf. bought one but i still have idle and off-idle issues.

 

the kicker is i replaced the front 02 around 1000-2000 miles ago as preventative.

 

i did the fuel filter and pump this past weekend for prep for a vf52.

 

will be taking the car to a shop of thursday for throttle testing. the same one that did my front 02.

 

Followup please?

 

I'm wrestling a p2138 pedal sensor code, that does not resurface if the MAF is unplugged.

 

I'm about to try plugging MAF back in and unplug front O2, to see if that also keeps p2138 away (dead pedal and limp home idle).

FWIW, if you need a TPS I put a link in JmP's sticky up top, where the cost for the sensor is like $25.00. It happens to be the same unit as a TGV sensor.

 

Post number 169,

http://legacygt.com/forums/showthread.php/idea-web-links-saved-various-parts-219238p5.html

FWIW, if you need a TPS I put a link in JmP's sticky up top, where the cost for the sensor is like $25.00. It happens to be the same unit as a TGV sensor.

 

Post number 169,

http://legacygt.com/forums/showthread.php/idea-web-links-saved-various-parts-219238p5.html

 

That sensor would not fit 2006 Legacy 2.5i