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Thread: '05 Cavalier engine dies when at idle, in gear, and foot on brake

  1. Top | #13
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    That I know of the valve shouldn't move without power. They sure don't move after I've taken them out. Not that I've measured them, but just by looking at them it's the same(or not enough to make a change). Truth is if I pull one a new one goes in. Well, I did reuse mine in a self ported TB. No problems and no need to do the idle relearn. The computer did a few quick adjustments and it works great.
    They do have a "home" which they go to. Key on for a start and they move to where they were or need to be do to air pressure and temp(quickly). They start with the high idle and work down.
    All I know is GM stuff, others may do it in a different way, so he may be right on them. Remember they deal with all makes.
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    I found a good youtube video explaining exactly how the IAC valve works. Once I understood that, I tested basic functionality of the valve by simply unplugging it when the engine was cold and with the pintle in its fully retracted position, and observing that idle speed was 2500 RPM under those conditions. Then shutting the engine off, plugging the connector back in, and starting the engine, the idle speed was around 900 RPM, which is normal for my engine when cold. So I am confident that the IAC valve is working and communicating with the computer.

    I cleaned the throttle body, the IAC valve, and the chamber that the IAC valve lives in. TB wasn't very dirty, only an oily film. There were some carbon-like deposits on the pintle of the valve and inside the chamber.

    Verdict is not yet in on whether the cleaning has resolved the stalling issue. I have driven the car some without stalling. But the problem had been intermittent so I think it is too soon to declare victory just yet.

    Thanks again to nogo04cav and Sparkey. I will post again with any further developments.
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    Last edited by roger2; 08-17-2015 at 06:16 PM.

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    It is just something that has been a problem for some. In this case if the stalling could be solved by this easy "fix" then it was well worth it. If not it is a good first step and you should not have to do that again for a long time. Guess we are moving on to the next thing.

    Yeah that port didn't look too bad at all. Looks great now!
    More humans=more problems
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    I have not done enough testing to be convinced it is fixed yet. Please do not go away too soon


    I have ordered some general maintenance items including new spark plugs, ACDelco 91-841 double platinum. I have questions about installing those, if I may:

    -are plugs like these pre-gapped? If so, can I trust that the gap is correct or could it possibly get bumped out of spec?

    -any tips on safely removing the old plugs without damaging the head? Cold engine? Warm engine? Other thoughts?
    Last edited by roger2; 08-18-2015 at 12:21 AM.

  5. Top | #17
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    Think you may be jumping ahead, but it's better to be sure on the plugs. Yes they are pre-gapped if they are not to spec you could take them back. There is a risk of coating damage when trying to make adjustments to these plugs.
    Cold engine. Everything should be tight so adding heat would make it worse. Do not forget anti-seize, put that on the threads. Really it should be used on anything that is going into aluminum. Dielectric grease is a good thing for electric connections, it helps with the connection and keeps moisture out.

    If I leave you hanging then it is because I'm at a loss for info. In that case we both need to wait for someone else.
    If you get some down time check all vacuum lines and main grounds for the electrical system. Those tend to be overlooked things that cause major problems. Oh and the wire to a sensor that is rubbing on something and is now shorting out. You know the kind...when driving it's fine, but when stopped it ends up getting in contact with something have a short time.
    More humans=more problems
    Don't worry nothing will be done until it's too late, there is money to be made.
    Maximum profit and overpopulation will ruin all the major economies.

  6. Top | #18
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    Do not forget anti-seize, put that on the threads. Really it should be used on anything that is going into aluminum.
    nogo04cav Quoted Post
    Strongly agree with the first part when installing spark plugs, strongly disagree with that second part. If no anti-seize or assembly lubricants are called for then none should be used. Adding things like anti-seize when not called for alters the torque value required for the bolt.

    I always check the gap on pre-gapped pugs, once in a while you do run across one out of spec. If I didn't install the plugs or they haven't been changed before, I try to change them cold if possible. If they are difficult to break don't panic, they are the originals which can be. When reinstalling, don't over tighten which is too common. They don't need to be as tight as you may think, it's only ~15 lb-ft so not much.

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    updates...

    Thanks again to nogo04cav and Sparkey

    updates:

    -the engine stalled again after cleaning the IAC valve
    -I discovered a physical crack in the body of the TPS
    -installed the new parts mentioned above (spark plugs, fuel filter, gas cap) as well as a new TPS
    -cleaned the contact areas on all of the main electrical cables - battery, main ground, ground strap from block to head

    I did all of the above without taking time to test at each step. And...

    ...pretty sure now that the stalling problem has been solved The engine has been running great!

    I don't know which of the things that I did affected the stalling issue. There was a bit of corrosion on all of the electrical connectors. The plugs, although having only 68k miles, did not look perfect. On one plug the little pip on the outer electrode had burned away, causing the gap to be maybe .010 greater than it should have been. And the crack in the TPS was something that obviously needed to be addressed, although I don't know if it was causing the stalling because the stalling only happened then the throttle was fully closed.

    In the pic below, the 2nd plug from the left is the one with the greater than ideal gap. Another plug had opened up a little. And two of them were pretty close to spec. I installed the new plugs without anti-seize, with dielectric grease only on the ceramic body (not on the metal), and torqued to 15 FT LBS.

    DSCN0276 resized.JPGDSCN0271 resized.JPGDSCN0267 resized.JPG
    Last edited by roger2; 09-21-2015 at 05:07 PM.

  8. Top | #20
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    Thanks again to nogo04cav and Sparkey

    updates:

    -the engine stalled again after cleaning the IAC valve
    -I discovered a physical crack in the body of the TPS
    -installed the new parts mentioned above (spark plugs, fuel filter, gas cap) as well as a new TPS
    -cleaned the contact areas on all of the main electrical cables - battery, main ground, ground strap from block to head

    I did all of the above without taking time to test at each step. And...

    ...pretty sure now that the stalling problem has been solved The engine has been running great!

    I don't know which of the things that I did affected the stalling issue. There was a bit of corrosion on all of the electrical connectors. The plugs, although having only 68k miles, did not look perfect. On one plug the little pip on the outer electrode had burned away, causing the gap to be maybe .010 greater than it should have been. And the crack in the TPS was something that obviously needed to be addressed, although I don't know if it was causing the stalling because the stalling only happened then the throttle was fully closed.

    In the pic below, the 2nd plug from the left is the one with the greater than ideal gap. Another plug had opened up a little. And two of them were pretty close to spec. I installed the new plugs without anti-seize, with dielectric grease only on the ceramic body (not on the metal), and torqued to 15 FT LBS.

    DSCN0276 resized.JPGDSCN0271 resized.JPGDSCN0267 resized.JPG
    roger2 Quoted Post
    The dielectric grease should go on the contact points, in other words the metal. It really is not doing its job where it is now. I can tell you that the first set of plugs I put in my old DD didn't have anti-seize and when they were pulled to be replaced 5k later(old style plugs) they took the top threads with them. After that all my plugs get anti-seize, hell of a lot cheaper than a new head.
    I'm happy that the car is running great though!
    More humans=more problems
    Don't worry nothing will be done until it's too late, there is money to be made.
    Maximum profit and overpopulation will ruin all the major economies.

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