Transmission issues

Tiny
CHERIEC
  • MEMBER
  • 2000 CHEVROLET IMPALA
  • 3.8L
  • V6
  • FWD
  • AUTOMATIC
  • 170,000 MILES
I recently bought a 2000 chevy impala ls. I had to replace the fuel pump along with the line and a few other items to the 3 stage fuel system. Also a complete tune up with new plugs and spark plugs. The work was done by a friends back yard mechanic that's done work on my cars for 10 years now. I was at work the day he competed the work and he left my idle running high. He told me it just needed to be driven for the computer to reset, that didn't work. I read a forum online saying to unplug the negative battery cable, let car run in neutral with ebreak on until fan kicks on then turn car off turn back on, pit it back in neutral with emergency break on again. Now my transmisson is slipping going into 2nd and It didn't do that before the fluid was at level. I went to work car sat for 4.5 hours to cool got off went to corner gas Station by my job which is a block away and checked the transmission it seemed real runny, but full. I want to do a flush on the transmission for my car to see if that helps, but I can't find anything online that's step by step for my car. I obviously did wrong with resetting the computer for the idle because all I needed to do was unplug the negative and plug it back in. I just hope you don't say I ruined my transmission!
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Tuesday, April 18th, 2017 AT 8:38 PM

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Tiny
CARADIODOC
  • EXPERT
I'm not sure what you're asking, but I can clear up some misinformation. The idle speed is indeed controlled by the Engine Computer, but the last thing you want to do is disconnect the battery. Each time you reconnect it, the computer has to start relearning things all over again. Some things take time and some only take place during specific conditions during the drive cycle. In the case of the idle speed, if that is too high, that is usually the result of a vacuum leak.

I've never seen all those steps you listed for doing relearns in any service manual. About the only thing they didn't tell you was to rub your belly while patting yourself on your head. There are a few things you can adjust on some car models, but those usually apply to customer convenience things like horn chirps with remote power locks, and sometimes with programming a new key. There's a real lot of things the computers are going to relearn, but for almost all of them you won't notice any symptoms or know those things are taking place.

You need special equipment to perform a transmission flush. That is only done in a shop, but you will rarely solve a problem. This doesn't make sense:

"Now my transmisson is slipping going into 2nd and It didn't do that before the fluid was at level.".

If the fluid level is not correct, the cause must be identified and corrected. If the level is correct, and there's a mechanical problem inside the transmission, the flush won't fix that. In fact, too many people have an existing transmission problem, have it flushed, then unfairly blame the flush procedure for causing the transmission problem. Other than clutch plate wear, most shifting problems can be attributed to a plugged filter or the need for the computer to relearn the wear characteristics in the transmission. This again has to start from scratch after the battery was disconnected. It can take a dozen miles and multiple shift cycles before the data is relearned and updated. Until then, shifting issues can be expected.

If you continue to have shifting problems, the first thing is to have the diagnostic fault codes read and recorded. If there are none, consider performing a fluid and filter change. If that doesn't solve a problem, a flush won't either.
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Tuesday, April 18th, 2017 AT 10:42 PM
Tiny
CHERIEC
  • MEMBER
Thank you for the information! The question I was meaning to ask was how could I do the flush myself. I just caught up with what I did wrong because I know I'm the reason the transmission is acting funny now. I'm happy to read about the car needing to relearn the transmission because that's what I truly believe is wrong. It had no issues before I did the the steps in the pictures I provided. Don't even ask why I would do it lol. I don't have the cash to go to a shop right now and I need my car to be in working order. I'm going to hope that after a day or so of driving that it fixes itself. I will also take it to my near by auto part store for a reading for help on it as well again thank you for the information.
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Tuesday, April 18th, 2017 AT 10:54 PM
Tiny
CARADIODOC
  • EXPERT
Sorry that I didn't take the time to explain it more clearly. You can't do a transmission flush yourself. The shops that offer the service use a special machine costing over $2,000.00. It connects to the cooler lines to pump the fluid in and out.

What YOU can do, if you don't mind getting messy, is the fluid and filter replacement. That only gets about half of the old fluid out, but the important points are the filter gets replaced, and the new fluid has plenty of additives in it to meet the needs of the transmission.

The charts you posted are for much older cars. There were some weird procedures when throttle position sensors were a new thing and were stuck inside computer-controlled carburetors. I wrote a paper on the 1980 models for a graduate class in college that covered them under "new technology". The first clue was the reference to the idle speed adjusting screw. No engine has had that since the mid to late '80s. When we did have those, air could enter the engine through the partially-opened throttle blade, which we could adjust, and through the controlled air passage around the throttle blade, which is what the computer uses to set the idle speed. If you adjust the idle stop screw for a higher idle speed, the computer will just come along and close the valve more to bring the idle speed to where IT wants it to be.

On your engine, the idle speed motor is the same exact part that is used on Chrysler products. The computer pulses the motor to one of 256 positions, and as it rotates the armature very slowly, it is turning a threaded rod that has a pintle valve on the end. As the steps increase in number, more of the valve opens up, and more air can bypass the throttle blade. For a properly-running engine, step 32 is typically what you'll find it set to. With a single-cylinder misfire, you can expect to see it on around step 50. In the case of Chrysler products, if "minimum throttle" hasn't been relearned after the battery was disconnected, idle speed will be too low, and stalling and hard starting are common unless you hold the accelerator pedal down 1/4". This is a case where the drive cycle I mentioned becomes the issue. A very specific set of conditions, including unusually-high intake manifold vacuum, and a perfectly steady reading from the throttle position sensor, are required for the computer to know when your foot is off the accelerator pedal. All of the relearn conditions are met by driving at highway speed with the engine warmed up, then coasting for at least seven seconds without touching the pedals. Moving the accelerator pedal, (throttle position sensor) or tapping the brake pedal, cancels the relearn.

The clue the instructions you were given did not come from GM is the phrase, "That should do it" in step 8. Technical manuals, to include manufacturers' manuals, are never written like that. Those instruction were written by a technical person. They just wouldn't appear in the service manual that way. This is how a description would be written on a consumer-level web site to disseminate information.

I'm going to add your post to my list of information that needs to be remembered. I post Chrysler's relearn procedure three or four times per week, and have it memorized. I've never been asked about older GM cars yet, but when the day comes, I'll be ready. Thank you.
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Tuesday, April 18th, 2017 AT 11:49 PM
Tiny
CHERIEC
  • MEMBER
Thank you for the information! I wish I had asked how to do the idle through here rather me goggle it and obviously do what's wrong. I will take the car on the freeway today and let it coast to see if that will help. With me following the steps in the picture do you think I runied my transmission? I didn't complete the steps after 5 because it was back at regular idle speed so I just stopped. Idle has remained normal. Now I just worry that I runied my transmission.
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Wednesday, April 19th, 2017 AT 7:24 AM
Tiny
CARADIODOC
  • EXPERT
You can't damage a transmission by programming something or following wrong steps. That would lead to a real lot of angry owners. The only thing you can do is continue forcing the car to move after symptoms have shown up due to an already existing problem. For example, a fluid leak that is ignored will eventually lead to slipping clutch packs. Pressurized fluid is used to apply the clutch packs and make the plates grab each other. When the fluid gets low, air gets sucked up instead, and that can be compressed. The clutch plates don't have enough pressure to grab, so they slip, then generate heat, and continue to tear up the fiber clutch plates even more. That damage will become severe within less than a mile. That is an example of how you can cause damage to the transmission, but only after something else initiated or led up to the failure.
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Wednesday, April 19th, 2017 AT 3:39 PM
Tiny
CHERIEC
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I want to thank you for the all yhe useful information you've given to me. I was able to take the car to Auto Zone this morning before work and the codes read back that I need to replace my Throttle Position Sensor. So I will now focus on that. I'm sure I am good to go for awhile after this, at least that's what I'm praying for. Again I thank you for your Time and knowledge I hope you have a great day?
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Thursday, April 20th, 2017 AT 9:59 AM
Tiny
CARADIODOC
  • EXPERT
Now let me add another chapter to my wondrous story. Diagnostic fault codes never say to replace a part or that one is bad. They only indicate the circuit or system that needs further diagnosis, or the unacceptable operating condition. When a part, such as a throttle position sensor, is referenced in a fault code, it is only the cause of that code bout half of the time. First we have to rule out wiring and connector terminal problems. If no problem is found there, we next use a scanner to view live data, and observe what the Engine Computer is seeing for a signal voltage from the sensor. If that looks okay, since this sensor is a mechanical device, it can develop a little chip of debris inside that occasionally prevents it from sending an accurate signal voltage. The Engine Computer can detect that momentary glitch when we can't see it fast enough with our eyes. Those intermittent problems can cause elusive intermittent running problems that would be impossible to diagnose with the fault codes to tell us which circuit to look in.

Reading and recording the fault codes is just the first step. If your mechanic followed through with the rest of the tests on the circuit, then I would agree with his diagnosis. You can replace the sensor yourself. The computer will relearn its characteristics, so no adjustment is necessary. If your plan to replace the sensor is based solely on the fault code, and no additional testing was done, don't get excited if the fault code sets again and the sensor doesn't solve the problem. At least you know the circuit that needs to be looked at, and there's only three wires in it.
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Thursday, April 20th, 2017 AT 3:19 PM

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