Throttle Position Sensor High idle and High RPM's

Tiny
SREPW
  • MEMBER
  • 2003 BUICK ALLURE
  • AUTOMATIC
  • 175,000 MILES
Problem started a while back where car would go into basically cruise control when took foot off pedal. I then realized it was idling very high (There is no idle gauge, but sounded that way). After a couple days it started stalling especially in idle.

I went ahead and finally purchased a OBD scanner tool and read codes. I was getting a P0121 (Throttle/peddle position sensor/switch A circuit range/performance) and a P0001 (fuel volume regulatory control circuit/open) together with a old P0420 (catalyst system efficiency below threshold).
At this point of time car would only drive a mile or two before stalling and I would have to wait about seven minutes for it to relax before starting it up again.
I decided to replace TPS and did that with a cheap autozone $35.00 a piece. (What a pain getting those screws out. Ended up cracking the old TPS and then cracking new one and putting in with only 1 screw.)
Car seemed to work fine for about a week. I went ahead and reset codes and of course right then car dies again.
Here's info I'm getting. Car idled at about 1800 rpm's and it goes up from there. Throttle position at startup is at about %38 (!). When driving car throttle acts erratically. Does not work contingent on pedal. Goes up and down erratically.
This morning started up car without the air conditioner and miracle the throttle was open about 0.5 RPM was at about 700 and throttle opened with direct correlation to gas pedal! After arriving at work (only a few blocks away) tried a few times and all was well. I then turned on the air conditioner and all went crazy again exactly as before. Turned off the air conditioner and stayed same (with Throttle position and RPM). Turned off car and restarted and stayed the same erratic.
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Tuesday, July 5th, 2016 AT 10:30 AM

12 Replies

Tiny
SREPW
  • MEMBER
Some more possibly important information. I removed the TPS and MAF completely (a few cables that connected them as well) and watched the throttle. Throttle seemed closed, but was getting reading of %70 open. Pressed down on the gas and throttle seemed to open and close alright, but I was getting readings that didn't correlate with what I was seeing with the throttle!Check engine went on and I am seeing a couple codes. I am getting under confirmed P0102 (mass or volume air flow circuit low input) and a P0502 (vehicle speed sensor "A" circuit low input) under the freeze frame heading I am getting a P0001 (fuel volume control circuit/open). Under the pending heading I am getting a P0121 (Throttle/Pedal position/Switch "A" circuit range/Performance). I imagine that the first two codes are because I disconnected the MAF and cables. The other two codes are what we got before resting.
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Tuesday, July 5th, 2016 AT 11:10 AM
Tiny
WRENCHTECH
  • EXPERT
70%? Are you sure that was not.7v instead?

Can you see what is hold the throttle plate open?

Can we be sure someone did not mistakenly adjust the throttle stop attempting to adjust the idle speed?
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Tuesday, July 5th, 2016 AT 12:00 PM
Tiny
SREPW
  • MEMBER
@wrenchtech, thank you so much for responding, I am using an obd that connects to my iPhone and it does not have option to view volts. It definitely was 70 percent.
I am not sure what you mean by second Q. It is a bit unclear.
Unless someone decided to play with the throttle stop while I was sleeping, I am not sure how such a thing would have occurred.
Interested enough I just drove about two miles with car. (Something that car has not been able to accomplish in awhile.) This time though the air conditioner was off. The throttle position was shown at a starting point of 38 percent, but the RPM's were perfectly normal!(?) When I hit the gas the throttle position did show a larger percentage, but did also seem to be somewhat erratic. Would drop and surge a lot.
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Tuesday, July 5th, 2016 AT 1:33 PM
Tiny
WRENCHTECH
  • EXPERT
You definitely cannot live with those readings. First you need some better equipment so you can read the actual voltage at the TPS. You need to have a slow, gradual increase in voltage as the throttle is slowly opened, ranging from about.5V to 4.5V.

The comment about the idle stop refers to some people think they can adjust the actual idle speed with the idle stop screw but in reality it totally messes things up. You need to find out what is stopping the throttle plate from closing all the way if that is really happening.
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Tuesday, July 5th, 2016 AT 2:12 PM
Tiny
SREPW
  • MEMBER
Thanks again for all your help. Here is the thing. When I removed the MAF and was able to see throttle, it looked to be completely closed even though was showing reading of 38 percent.
Also, can I get a voltage reading with a multi-meter?
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Tuesday, July 5th, 2016 AT 2:18 PM
Tiny
WRENCHTECH
  • EXPERT
Yes, you can if you tap into the right wire. It is usually the middle one.
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Tuesday, July 5th, 2016 AT 2:22 PM
Tiny
SREPW
  • MEMBER
Okay, now this is really strange. I imagine I am doing something wrong. Trying to test car with multi-meter (which I have not ever used before). I am getting no readings anywhere (battery or fuses). I am testing it on friends 2010 Camry and getting regular readings. What in the world am I doing wrong?
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Tuesday, July 5th, 2016 AT 3:15 PM
Tiny
WRENCHTECH
  • EXPERT
You have to switch it to DC volts and attach the black lead to negative battery terminal and take you measurement with the red lead.
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Tuesday, July 5th, 2016 AT 4:15 PM
Tiny
SREPW
  • MEMBER
I did that. (I got readings on friends car)
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Tuesday, July 5th, 2016 AT 4:50 PM
Tiny
WRENCHTECH
  • EXPERT
You are either on the wrong wire or the sensor is bad assuming you are using the meter right. Test it on the battery itself to see if it reads.
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Tuesday, July 5th, 2016 AT 4:52 PM
Tiny
SREPW
  • MEMBER
I tested it on battery and still no reading *scratching head.
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Tuesday, July 5th, 2016 AT 4:56 PM
Tiny
WRENCHTECH
  • EXPERT
Okay, then you just have a problem operating the meter. Probably time for a professional to look at it.
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Tuesday, July 5th, 2016 AT 4:58 PM

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