C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

I need help big time

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Old Aug 24, 2020 | 02:26 PM
  #21  
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With the pipe going red hot and the other pipe normal I would think you would look for a physical problem first. Cat problem, may not be fully clogged but coming apart inside and the flow is disrupted or something. Air added somewhere above. Maybe a cracked manifold. Once the physical problem option has been removed as a possibility I would consider the cable linked in this thread above so you can watch it live and let it tell you exactly what's going on. Otherwise its just throwing darts until you find it. That get's expensive and even more frustrating fast.

If you do go down the Opit road again before you throw another penny at it search up and consider the LTCC coil per cylinder option. That will remove the opti from the equation forever and it looks cool.

https://www.corvetteforum.com/forums...post1601954490


Last edited by Furias15x; Aug 24, 2020 at 02:31 PM.
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Old Aug 24, 2020 | 02:37 PM
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a bad ECM can cause this and it happens suddenly. It also is a PITA to diagnose because since it is bad the codes generally are not helpful because the ECM doesn't just set a code that says "I'm bad"
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Old Aug 24, 2020 | 02:41 PM
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Originally Posted by vetteLT193
a bad ECM can cause this and it happens suddenly. It also is a PITA to diagnose because since it is bad the codes generally are not helpful because the ECM doesn't just set a code that says "I'm bad"
Oh how this is so true. If only it could tell us "I am really not feeling well today"

Last edited by Furias15x; Aug 24, 2020 at 02:41 PM.
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Old Aug 24, 2020 | 02:51 PM
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Originally Posted by vetteLT193
a bad ECM can cause this and it happens suddenly. It also is a PITA to diagnose because since it is bad the codes generally are not helpful because the ECM doesn't just set a code that says "I'm bad"
Sometimes they do, you just have to hear what it is trying to tell you. For Example:

If Code 12 doesn't come up, that is the dummy check for if the ECM functioning properly

If you get codes for features not on the vehicle, this points to a faulty ECM as well. I had my TTA throw a Code 53 on me back in the day - Water Injection... never used from the factory. So, It was an indication the ECM was bad. Replacing the ECM fixed all the running issues with that car.

Another is when the ECM throws a large amount of seemingly unrelated codes together suddenly.

I thought he said he had swapped ECMs though.

Last edited by KyleF; Aug 24, 2020 at 05:30 PM.
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Old Aug 24, 2020 | 03:27 PM
  #25  
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Originally Posted by Y-ME
Car ran fine after that, and now have factory 22lb



So let me ask again, do you have any mods besides the injectors and the rockers?

I understand you switched from the 28's back to the 22's
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Old Aug 25, 2020 | 07:25 AM
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With that mileage, how about the timing chain jumped a tooth??
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Old Aug 25, 2020 | 07:49 AM
  #27  
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You need a good scan tool which you can use as you drive. My Innova Scan tool picks up caution codes prior to actual codes. It is like a warning that something if you do not isolate a hard code will display.Another suggestion go to local corvette only shop and ask questions they have seen many situations like yours.
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Old Aug 27, 2020 | 02:41 PM
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As I mentioned I switched out the ECM with a 94 I parted out, same
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The only time I have seen glowing pipe was for timing to be way late. I would go old school. Chalk a TDC mark, 10 degree BTC mark, 20 BTC mark. and get a timing light.
8 inch pulley. 8times 3.14 = 25.12 around the outside. 25.12 divided by 360 = .07 per degree. A little less then 3/4 of an inch for 10 degrees. 1 7/16 for 20 degrees.
Does not take long to do. Put the mark to align with something you can get a light at and still get a look.
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