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1993 Buick Lesabre Self Acceleration

Tiny
INTOSILENCE1
  • MEMBER
  • 1993 BUICK LESABRE
  • 3.8L
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 149,000 MILES
My 1993 Buick Lesabre somtimes accelerates on its own. Sometimes it does it as soon as I turn on the car, it sounds like if im stepping hard on the gas. Other times it happens after I have been driving for a while, when I have to break I have to step on the brake hard because it wants to speed up, and it wont stop until I turn it off again. Someone told me that one of the vacuum lines connected to the throttle body could be damaged, so I checked and a couple of the rubber elbows were badly cracked so I replaced them. But it's still doing it. What could be the problem?
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Friday, July 24th, 2015 AT 12:56 PM

53 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,244 POSTS
Have you checked for other vacuum leaks including around the intake? Also, have you checked for trouble codes?
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Friday, July 24th, 2015 AT 9:28 PM
Tiny
INTOSILENCE1
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Im sorry im a bit of a beginner, how exactly do you check for trouble codes?
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Saturday, July 25th, 2015 AT 4:37 AM
Tiny
INTOSILENCE1
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  • 79 POSTS
Well I cheched for leaks, nothing. I cleaned the throttle body intake as well as the IAC hole, (which were both dirty) and it's still doing it. I haven't checked for trouble codes because they charge me $40 just to check it. Which means if I spend what I have on that, I won't have enough to buy whatever piece needs replacing. Any other ideas?
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Sunday, July 26th, 2015 AT 3:36 AM
Tiny
JACOBANDNICKOLAS
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Watch this video and let me know what you find.

http://www.youtube.com/watch?v=V8nZpQyoRh4
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Monday, July 27th, 2015 AT 9:44 PM
Tiny
INTOSILENCE1
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  • 79 POSTS
Well I tried it but it didn't work. I suppose i'll go get it checked with the actual machine. Thanks though.
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Tuesday, July 28th, 2015 AT 7:55 AM
Tiny
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Did anything happen? It should have at LEAST flashed a code 12 which indicates the system is in diagnosis mode.
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Wednesday, July 29th, 2015 AT 7:31 PM
Tiny
INTOSILENCE1
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  • 79 POSTS
Ok I got it to work. Apparently, in my car you're supposed to insert the 2 tips of the paperclip on the last 2 holes on the LEFT side of the BOTTOM row of the trouble codes plug, not on the TOP RIGHT side like the video you posted says. Anyway, it flashed 2 times slowly, and then 3 times quickly. Im guessing that's code 23. If it is, I googled it and it says it means "Manifold Air Temperature - Low Reading." BUT. In other parts of the Internet it says it's the IAT sensor. So which one is it and what do I do? Thanks.
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Thursday, July 30th, 2015 AT 11:21 AM
Tiny
INTOSILENCE1
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Ok a few updates since my last message. I replaced the Iddle Air Control Valve with a brand new one. The acceleration does appear to be just slightly smoother and faster. The "Check Engine" light hasn't shown up at all. BUT. The self accelerating thing is still happening. Not as much or as hard as before, but it's still there. I checked for trouble codes again, and it keeps giving me code 23 (assuming that's what 2 slow blinks and 3 quick blinks mean). What else is there?
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Thursday, July 30th, 2015 AT 2:53 PM
Tiny
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Okay, the two things you mentioned are the same item. IAT stands for intake air temperature. That is the same as manifold air temp. If you are correct, that sensor needs replaced.

Now here is my concern. When you first turn the key on with the paper clip installed, you should get the code 12, three times, and then a slight delay, and then any trouble codes. Are you getting the 12? Also, if you take a flash light and look into the connector, how many of the ports have a wiring connector in them?
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Thursday, July 30th, 2015 AT 8:30 PM
Tiny
INTOSILENCE1
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  • 79 POSTS
Well when I first turn the key to ON with the paperclip inserted, it flashes 2 times slowly, and then 1 time quickly. If you add that up it's 21, which doesnt make senses if you're saying im supposed to get 12. My question is, could a faulty IAT sensor cause the car to accelerate on its own? Because the guy from the local Autozone store that checked the trouble codes with me, said that a bad IAT wouldn't cause that? Is this true?
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Thursday, July 30th, 2015 AT 10:24 PM
Tiny
INTOSILENCE1
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Oh and to further specify, when I turn the key to ON, it flashes 2X slow and 1X fast, this repeats 3 times. Then there's a delay, and it flashes the trouble code (2 slow blinks and 3 fast blinks). This also repeats 3 times. After that there is another delay, and it starts doing the first pattern again (2 slow blinks and 1 fast one).
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Thursday, July 30th, 2015 AT 10:32 PM
Tiny
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Okay, I think I know what you are seeing. Two slow ones then a fast. The first slow is the number 1 then a delay, then two quick? I believe that it may be indicating a code 12 which means the system is in diagnosis mode. Is that possibly what you are seeing?
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Sunday, August 2nd, 2015 AT 9:34 PM
Tiny
INTOSILENCE1
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Yes im sorry about the confusion. It actually flashed 1 time slowly and then 2 times quickly (so yes thats code 12). It flashed code 12 three times and then it flashed code 23 also 3 times, then back to code 12. But here's the thing, yesterday I replaced the Intake Air Temperature sensor with a brand new one. I checked for trouble codes again, and all it gives me is code 12 over and over again. So no more bad codes. But it's still doing it. I already checked for vacuum leaks, I cleaned the TB and the MAF sensor, I replaced the IAC valve and IAT sensor. What else did I miss?
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Monday, August 3rd, 2015 AT 10:59 AM
Tiny
INTOSILENCE1
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Hey sorry to bother again. Just today the Engine Light came on again and this time it flashed code 22, which Google says it's the Throttle Position sensor - low reading. I don't know why it hadn't flashed it before, but now it did. So am I correct to assume that I have to replace the Throttle Position sensor?
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Friday, August 7th, 2015 AT 5:49 PM
Tiny
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Before replacing it, check all connections to it and check voltage to it. If you need me to, I can try to find the process to actually test the TPS.
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Saturday, August 8th, 2015 AT 5:32 PM
Tiny
INTOSILENCE1
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If you think that's the best thing to do then by all means. I just hope its not an expensive process, because Im pretty broke right now. Thanks a lot for your help.
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Saturday, August 8th, 2015 AT 6:38 PM
Tiny
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I would suggest it, but it will require a scanner to do the test. See if there are any parts stores that will lend you one or rent one to you and let me know what you find.

I attached a flow chart for checking the TPS. Let me know if it helps you.

Joe
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Sunday, August 9th, 2015 AT 8:02 PM
Tiny
INTOSILENCE1
  • MEMBER
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Well friend it's mission accomplished. I wasn't able to get a hold of a multimeter, so I just proceeded to change out the TPS. The problem is gone now. Engine Light didn't turn on anymore. I checked for trouble codes again, and no more bad codes. Acceleration feels even smoother. And when I set it on Park, acceleration dies instantly. So fortunately, it appears there was nothing wrong with the wires or the ECM. Thanks again for all your help and for hanging in there. Have a nice day.
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Monday, August 10th, 2015 AT 5:07 PM
Tiny
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Good job. I'm glad you got it fixed. Let me know if you need anything in the future.

Joe
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Saturday, August 15th, 2015 AT 7:32 PM
Tiny
INTOSILENCE1
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Hello again Joe. I have a new question I was hoping you could help me with. Sometimes when I crank the car, it sounds like it stalls a bit before starting, compared to other times when it starts right away. Anyway, after briefly stalling, the roar of the engines sounds irregular or like in small waves. Instead of one long Rrrrrrrrrrrrrrrr, you hear rrrr rrrrr rrrrr rrrrrr. This goes on fot about 5 seconds and then it returns to normal. Im not sure if its air or a liquid being unevenly distributed, but it sounds like its one of the two. Any ideas?
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Friday, August 28th, 2015 AT 5:04 PM

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