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1st post engine help

This is a discussion on 1st post engine help within the General Help forums, part of the LSx Technical Help Section category; I have been a long time lurker and just recently signed up because I have a problem. I have a ...

  1. #1
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    1st post engine help

    I have been a long time lurker and just recently signed up because I have a problem.

    I have a 1999 fixed roof coupe Corvette with 20,000 miles. The car is like new. BUT.

    I drove it yesterday without a hickup.

    Today, I started it up with no problems, went to roll up the passenger window and it stops about half way. Then I hear a ding and the check tire pressure message was up, then it said, reduced engine power. I scrolled through the list and the tire-pressure was blank - then the engine turns off but I have accessory power. I started it up again and the same thing happened.

    I would think it was the battery going haywire but its a new battery (within the last 3 months) and everything is fastened down fine.

    Has anyone ever heard of anything like this? Sounds like somethig is not getting enough power and its making the computer go spastic. I can't imagine all of those functions going out at once.

    Any ideas?

    Its a 6 speed.

  2. #2
    Member 89LX's Avatar
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    Welcome to the site. I am sure someone will assist you. Nothing short of a wealth of experience found here.

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    Thanks!

    Anyone have any ideas?

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    Veteran 0rion's Avatar
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    I meant to look into this last night and forgot. Did you wash the car? I know the y-bodies are infamous for leaking water out of the cowl onto the pcm and causing all sorts of electrical problems. This would be the first time I've ever heard of one dying from it though so that may not be your problem. I would maybe also pull that battery and have it tested. I know you said it's basically new but strange things have happened. I would also have the alternator tested while you were at it just to rule it out. Were those the only codes you threw? Tire pressure and reduced power? Normally a water problem will throw no communication codes too along with 5-6 more. Let me do some reading and I'll see if I can find anything else out for you.

  5. #5
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    Quote Originally Posted by 0rion View Post
    I meant to look into this last night and forgot. Did you wash the car? I know the y-bodies are infamous for leaking water out of the cowl onto the pcm and causing all sorts of electrical problems. This would be the first time I've ever heard of one dying from it though so that may not be your problem. I would maybe also pull that battery and have it tested. I know you said it's basically new but strange things have happened. I would also have the alternator tested while you were at it just to rule it out. Were those the only codes you threw? Tire pressure and reduced power? Normally a water problem will throw no communication codes too along with 5-6 more. Let me do some reading and I'll see if I can find anything else out for you.

    That is interesting. I washed it the day before last (didnt wash the engine of course) but I drove it the following day with no problems.

    Thanks man. Those were the only codes. I plugged my obd2 reader into it and it was all clear (which makes sense - no check engine light). Ill pull the battery and put an optima in it. It has some gereric one in it (although pretty new).

  6. #6
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    The tire pressure sensor PSI will be blank until you drive the car about a 1/8 mile or so--It has to read the sensor as the rim turns round and round past the pick-up----ALSO this happened to me so I know it's true--If the tire pressure falls below 20 PSI you will get the reduced power message and the engine will die and go into limp home mode---( I let my rears down to 18 psi at the dragstrip and when i punched off i got to about 50 MPH and the reduced power message came on--engine died and i almost hit the fence as i lost power steering & brakes--I started it back up and it would only drive 25 mph all the way back to the pits) scared me more than anything as i wasn't expecting it
    As far as the window goes--don't know unless it is a part of the limp home mode to shut down all accesories when activated

  7. #7
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    00 LS1, WS6, V8 Gremlin
    96 & 98 GTPs, 64 'Cuda

    ALthough I've never heard of those exact symptoms I do know an alternator that's getting flaky can confuse the entire electrical system. It will still loook like it's charging the battery but instead of putting out smooth DC they start putting out a bunch of hash too.

    Most auto shops/parts stores now have the capability to test for this as well as pure output now. Got one of those huge audio filtering caps? Try hooking it directly up to the alternator output and the alternator case (+ to + & - to - of course) See if you get a slight improvement.

    Tune your radio to a quiet spot near the low end of the AM band. A quiet smooth whine that changes with engine RPM is normal, and erratic one is not.

    Another possibility is a poor ground connection from the battery to the car body &/or engine block &/or between them. Sometimes you can spot these with an ohmmeter by disconnecting the NEGATIVE battery cable, attach one end to the loose negative cable then measure the ohmage to the block and to the car body. A better way is to start the car and turn on about every accessoriy you can, then measure the voltage drop using the negative battery terminal (that you've hooked back up again of course) as the reference then probe the car body to see if there's an excess voltage drop - likewise probe the engine block for any significant drop there.

    This equation can be used to determine the average voltage drop per 100 feet of any size wire gauge.

    To determine voltage drop per 100 feet given load current and wire gauge:
    VD = Voltage drop per 100 feet (Volts)
    IL = Current load (AMPs)
    AWG = Wire gauge

    VD = 0.1 X IL X 1.26^(AWG-10)

    [final thing is 1.26 raised to the power of (AWG - 10)]


    Same formula, but for paired cable:
    <A HREF="http://www.altronix.com/images/example2.gif">http://www.altronix.com/images/example2.gif</A>

    Reference page:
    http://www.altronix.com/index.php?pid=4&note=1

    More references:
    http://www.pupman.com/listarchives/1.../msg00222.html
    http://www.interfacebus.com/Copper_Wire_AWG_SIze.html

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