1993 Buick Lesabre Self Acceleration

Have you checked for other vacuum leaks including around the intake? Also, have you checked for trouble codes?

Im sorry im a bit of a beginner, how exactly do you check for trouble codes?

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?

Watch this video and let me know what you find.

http://www.youtube.com/watch?v=V8nZpQyoRh4

Well i tried it but it didn't work. I suppose i'll go get it checked with the actual machine. Thanks though.

Did anything happen? It should have at LEAST flashed a code 12 which indicates the system is in diagnosis mode.

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.

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?

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?

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?

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).

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?

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?

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?

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.

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.

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

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.

Good job. I'm glad you got it fixed. Let me know if you need anything in the future.

Joe

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?

Have you checked fuel pressure? It may be bleeding off a bit when the engine is off and taking a couple seconds for it to build pressure again.

No I havent. I understand you connect a pressure tester on a valve that's along the fuel lines that run on top of the engine. Thing is I dont have the money right now to buy a tester or take it to get tested. But just for the record, what could the possible cause if the fuel pressure does turn out to be low? That way I can start looking at prices for when i do get it tested and I end up having to replace something. Thanks.

It could be a few things such as a plugged fuel filter, weak or lazy pump, a leaking injector...

I'm not sure where you are located, but if you have any Auto Zones or Advance Auto shops near you, most of the time they will lend you tools. What they do is take the money for the cost of the tool to protect themselves and when you return the tool, they return the money. It's just a thought.

Well I live in south Texas and yes we have both stores available although i usually go to Autozone. I called them but they said they dont lend the tester out, they just sell it. I will try Advanced Auto tomorrow. As for your 3 theories, I think that a bad injector is more likely. I say this because I replaced the fuel filter about a year ago and from what I've heard, it usually takes longer for it to get clogged to the point of needing replacement. As for the bad pump, Im inclined to think that's not the problem because I've read that when is bad, you experience a certain kind of jerking or loss of power when going at high speed. And honestly my car actually runs pretty smooth and doesn't lose power when Im going over 50 and i step on it hard until i reach 90 or so. And even when I keep at that speed for a little while, there's absolutely no jerking of any kind. So i guess my main question is, does the pressure tester pin point the exact cause of the problem or not?

If pressure is low, it indicates either a bad filter or weak pump. If it is normal and loses pressure quickly when you turn the key to off, it could be an injector leaking off.

Ok well I will get it tested as soon as I can and I'll let you know what I find. Thanks again.

Hello again. I am very close to buying the fuel pressure tester that I need for the previous problem i mentioned. But in the meantime i have another question. My car was recently leaking transmission fluid, so i took it to this place where they fix transmissions. They said that two of the seals/gaskets were cracked so they had to be replaced. One is supposed to go on the side of the transmission and the other one on the rear side of it. Anyway right after I picked up my car i noticed that once I hit 50 mph or so, the entire car started shaking pretty badly, you could see it especially on the gas and brake pedals and the steering wheel. It DID NOT have that before. I asked them beforehand to check if the torque converter bolts were loose because it did used to rattle a little but only when I had it on Drive and was holding the brakes at the same time. But before their service, I could've accelerated from 0 to 80 and not feel any continuous shaking. Now even the faint rattle it had while at idle feels worse. I plan to call them tomorrow but I just wanted to know you're opinion. Thanks again.

My first guess is that they didn't properly install one of the axles. And I'm not sure which seals they replaced. If one was an axle seal, they had to remove an axle to do it.

Well it turned out to be the tires that just needed balancing. Ok i just tested the fuel pressure with the new tester i bought, and as far as i can tell, pressure does seem low.
I found this piece of information on google, although i can't say if it's 100% correct. It said the pressure should be 48-55 psi (with ignition ON) and that there should be a 3-10 psi loss at idle. So I turned the key to ON, and it reads 43 psi, and it stays there. Then I turned the engine on, and it dropped to 36 psi, and stayed there. Then i turned the engine off, and in 30 seconds or so, it goes back to 43 psi, and stays there again. I repeated this process like 4 times, so these numbers are final. So while pressure is not extremely low, I've read that in fuel injected vehicles like mine, even slightly low pressure will affect it negatively.
So in your previous comment you said low pressure reading is caused by either a bad pump or a clogged filter. I will try the cheaper option first, and if the problem persists then it's got to be the pump right? I'll let you know next week when i change the filter. Thanks.

That sounds like a plan. Let me know.

Well I changed the fuel filter and i rechecked the fuel pressure with.the tester I bought and nothing has changed. The fuel pressure remains the exactly the same. The old filter didn't look very dirty either so that wasn't the problem. I know you said the other option would be a bad fuel pump, but do you think there's a chance it could be the fuel pressure regulator? Both parts are $100 each, so there's no cheaper option but the pump is so much harder to change on my car than the regulator. So if there's any chance that the latter could be the problem I would be very happy to try it first. What do you think?

If the pressure is within the manufacturer's specs, chances are both parts are good. Have you removed the vacuum hose to the regulator? If not, remove it and see if there is any gas getting into it.

Well i unplugged the vacuum line connected to the fuel pressure regulator and it did have a faint smell of gasoline. So does this mean my FPR needs to be replaced?

A few updates. I checked the vaccine line to the regulator again but this time with the engine running and it didn't really smell like anything. Also I read online about a test you can do to check for either a bad regulator or a bad pump/clogged filter. It basically consisted in moving the throttle with the engine on while having the fuel pressure tester connected. The pressure was supposed to rise about 5 psi, which it did. The other test was to unplug the vacuum line to the regulator with the engine on, in which case the pressure also to rise fom 5 to 10 psi, which it also did. So if we go by this test then both the pump and the regulator should be good. A friend told me that bad spark plugs also cause a rough or fluctuating idle. Is this true? I ask because it's been a couple of years since I changed them so i wouldn't be surprised if they're bad. Thanks.

MORE UPDATES: I changed the Spark Plugs and the wires, and while i did notice that the car now turns on instantly (unlike before that it would stall for a second), the erratic idling is STILL present. Also I called Autozone and they gave me the actual fuel rail pressure specified for may car: 41-47 psi with ignition ON. So my car's pressure's been good all along. So what's next?

Sorry I haven't gotten back sooner. Since the pressure is good, I need you to check engine vacuum. Basically, you need a vacuum gauge which is hooked up directly to an intake port. At idle, vacuum should be around 17-20.

Check that and let me know. And I'm sorry, but I can't remember which codes were present if any, and I can't find them looking back through our posts.

No codes present this time. I will try the vacuum test as soon as i can buy a tester. Might be a while though. I'll stay in touch. Thanks.

The reason I'm suggesting this is two fold. First, I need to make sure the compression is still good, and it will let us know if there is a leak that is unseen.

Ok hold on what's the name of this tester and where would i connect it because the guy from Autozone said they dont sell anything to check the vacuum lines. What exactly should i ask for?

It is a vacuum gauge. It hooks to a vacuum port on the intake. See pic attached.