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Thread: TBI ALDL info?

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  1. #1
    Fuel Injected!
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    With respect to the BLM and/or INT what would typical numbers look like given varying condition/s?
    1994 GM P-30 Southwind Storm 28ft
    454 TBI w/4L80E trans
    VIN #1GBJP37N4R3314754

  2. #2
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    If you are unsure of the condition of the engine components, the first thing you should be doing is replacing the O2 sensor. If this engine is still using the old TBI unheated one-wire O2 sensor, those are really not that great and don't last nearly as long as the heated O2 sensors that were introduced along with the sequential-injection LT1 in '94. So if you don't know if they've been replaced and you're unaware of their condition, just replace them. No sense chasing your tail looking at INT and BLM if the O2 sensor is not reacting accurately.

    As for fuel, just hook a pressure gauge up to the port on the rail and watch it under load. I'm not intimately familiar with TBI engines so I can't tell you what the proper base fuel pressure is for a 454 TBI. If you know the correct value, then a pressure gauge is an easy and cheap way to confirm. Plus you can check to make sure it's actually able to hold pressure while you're at it. Again, no sense chasing your tail over bad readings if the underlying problem is something mechanical and not the tune.

    If there's no IAT sensor, I'd wonder why that data is in the datastream. Hopefully it's just a bad datastream definition. If the ECM is actually trying to make corrections based on an IAT that doesn't exist, obviously that could be a problem. But again, I don't know enough about your engine to say.

    Good luck!

    As for BLMs, you should be looking for 124~132. Preferably 128 or lower. If you start seeing things going to 136 or higher, that's lean, so you'd be best to avoid that. But again, make sure your O2 sensor is actually good and your fuel pressure is solid before you try to mess around in the tune.
    1990 Corvette (Manual)
    1994 Corvette (Automatic)
    1995 Corvette (Manual)

  3. #3
    Fuel Injected!
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    Quote Originally Posted by NomakeWan View Post
    If you are unsure of the condition of the engine components, the first thing you should be doing is replacing the O2 sensor. If this engine is still using the old TBI unheated one-wire O2 sensor, those are really not that great and don't last nearly as long as the heated O2 sensors that were introduced along with the sequential-injection LT1 in '94. So if you don't know if they've been replaced and you're unaware of their condition, just replace them. No sense chasing your tail looking at INT and BLM if the O2 sensor is not reacting accurately.

    As for fuel, just hook a pressure gauge up to the port on the rail and watch it under load. I'm not intimately familiar with TBI engines so I can't tell you what the proper base fuel pressure is for a 454 TBI. If you know the correct value, then a pressure gauge is an easy and cheap way to confirm. Plus you can check to make sure it's actually able to hold pressure while you're at it. Again, no sense chasing your tail over bad readings if the underlying problem is something mechanical and not the tune.

    If there's no IAT sensor, I'd wonder why that data is in the datastream. Hopefully it's just a bad datastream definition. If the ECM is actually trying to make corrections based on an IAT that doesn't exist, obviously that could be a problem. But again, I don't know enough about your engine to say.

    Good luck!

    As for BLMs, you should be looking for 124~132. Preferably 128 or lower. If you start seeing things going to 136 or higher, that's lean, so you'd be best to avoid that. But again, make sure your O2 sensor is actually good and your fuel pressure is solid before you try to mess around in the tune.
    Much appreciated for the reply.

    I replaced the O2 sensor with a Delco one (single wire) just a few years ago. The engine runs great just getting a feel for the proper tune. This only has the (1) O2 which is before the muffler. I also have a fuel adapter fitting that I will install on the TBI inlet (replace the OE one) which I will then install a fuel schrader valve. This way I can quickly check the fuel pressure if need be. Bought the following...

    https://marine-performance-parts.com...843505774.aspx

    https://www.dieselorings.com/schrade...-1-8-mnpt.html

    Being a step above a traditional carb set up I'm curious why they were not leaning these engines out more at part throttle condition (say 15-16afr) to get it to run cooler given they had the ability with the advanced timing. In the air-cooled engine world VW/Porsche we can achieve cooler running temps with an AFR at 16:1 than at 13:1 with a vacuum advance and part throttle condition. The hottest zone would be 14-15afr under load/WOT...Deathzone. Given I'm rebuilding the TBI and replacing the regulator diaphragm that may aid in the pressure holding more steady and help the afr.

    The following illustrates this....https://www.advancedpilot.com/articl...articleid=1844
    Last edited by udidwht; 04-24-2023 at 06:25 AM.
    1994 GM P-30 Southwind Storm 28ft
    454 TBI w/4L80E trans
    VIN #1GBJP37N4R3314754

  4. #4
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    The '94 - '95 units run at 30 psi versus 13 psi for the previous units.

  5. #5
    Fuel Injected!
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    Correct. 26-32psi to be precise.
    1994 GM P-30 Southwind Storm 28ft
    454 TBI w/4L80E trans
    VIN #1GBJP37N4R3314754

  6. #6
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    Hiya,
    Your EGR passage is partially plugged causing the computer to add fuel.
    -Carl

  7. #7
    Fuel Injected!
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    How'd you come up with that?

    EGR is fairly new (1.5yrs) AC Delco. It is an electronic EGR (linear).

    Anyone know the EGR passage diameter & length of passage? I'll get a long flexible tube brush and run down it with some 'Deep creep'.

    Didn't appear to have excess build up when I replaced the EGR (due to age).
    Last edited by udidwht; 04-24-2023 at 03:21 AM.
    1994 GM P-30 Southwind Storm 28ft
    454 TBI w/4L80E trans
    VIN #1GBJP37N4R3314754

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