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Thread: Burning Rich

  1. #1
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    Burning Rich

    95 K1500 with the 5.7L. Alright, my truck is burning incredibly rich. It has been this way for as long as I can remember. I have done many things over time to it to figure out why, but nothing seems to help. I have done everything from changing plugs and wires to changing out the coil with a hotter spark in hopes of burning off the extra gas. I recently changed out the stock intake and TBI with an Edelbrock Preformer Manifold and a Holly 502-9 TBI so that I have more control over the air to fuel mix....still nothing.

    The only thing I can think of remaining that could be the problem is that I am running a true dual exhaust with a crossover and no cats. Could the lack of back pressure cause it to burn rich? I have had older model trucks, back in the glorious days of carbs, that I could run without cats and have no problems?

    Any help or advice would be greatly appreciated.
    Ryan
    95 Chevy K1500 Z71 Extended Cab
    383 Stroker, 400 HP, 485 Ft-Lbs Torque

  2. #2
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    Me thinks this could be one of two problems, (somebody out there is going to guess, I might say vacuum leak, lol), well, this is not too far off.
    A leak or faulty EGR can cause this, as could a faulty injector.
    Those two seem to be a reasonable place to look.

  3. #3
    Senior Member zombie1969's Avatar
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    Make sure you dont have any exaust leaks before or near the o2 sensor.Ive had one o2s read faulty with a leak after it if you can beleive that.Three guyes replaced the o2 before I got to it.Could also could just be bad and not setting a code.Another thing to check is the temp sensor.I think you have 2.1 for the guage or light and the other sends info to the computer.If the computer thinks the engin is cold it will keep a rich mixture.

  4. #4
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    You probably ought to check your coolant temp sensor. Any chance you put a 160 or 180 thermostat in?
    Joe
    89 K2500 Chevy, Wee-Oh-five 294K miles
    1962 Scout 80 parts I guess
    1966 Scout 800 resto job
    2005 Chevy 2500HD Short cab long box DURAMAX
    1996 P30, 6.5 NA Mac Mobile
    whole lot of buicks

  5. #5
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    Yes, I do have a 160 Thermostat in it, always have. I never noticed it burning so rich though.
    As for the EGR, I had it replaced when the air intake got swapped, but I'll test it as well.
    The O2 sensor was going to be my next replacement.
    The temp sensor I have never checked, I know that the one that sends the signal to the gage works, I bounced it off an infrared sensor.
    Thanks for the advice, I'll start the testing process.
    Ryan
    95 Chevy K1500 Z71 Extended Cab
    383 Stroker, 400 HP, 485 Ft-Lbs Torque

  6. #6
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    Quote Originally Posted by rbmcveigh View Post
    Yes, I do have a 160 Thermostat in it, always have. I never noticed it burning so rich though.
    As for the EGR, I had it replaced when the air intake got swapped, but I'll test it as well.
    The O2 sensor was going to be my next replacement.
    The temp sensor I have never checked, I know that the one that sends the signal to the gage works, I bounced it off an infrared sensor.
    Thanks for the advice, I'll start the testing process.

    Ditch the 160 thermostat. The ECM is NOT tuned for that temperature which will cause a rich condition. 195 Is what should be in it.

  7. #7
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    The truck is never coming out of closed loop mode with a 160 stat. you need to have it chipped to run at 160. Thats your problem.
    Joe
    89 K2500 Chevy, Wee-Oh-five 294K miles
    1962 Scout 80 parts I guess
    1966 Scout 800 resto job
    2005 Chevy 2500HD Short cab long box DURAMAX
    1996 P30, 6.5 NA Mac Mobile
    whole lot of buicks

  8. #8
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    Alright, so the Thermostat is probably the problem. Now the question of the day, I want to drop a 383 in. I understand there will be some issues with the computer and the TBI. Does anyone know of a good company/person that can remap the computer or sell the chip that I would need? I'd like to keep the 160 thermostat, so I want to remap anyways. I hate seeing the temp guage near boiling, especially under load.
    Ryan
    95 Chevy K1500 Z71 Extended Cab
    383 Stroker, 400 HP, 485 Ft-Lbs Torque

  9. #9
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    If you are planning on a 383 and serious performance, you should probably ditch the TBI at this point.
    Joe
    89 K2500 Chevy, Wee-Oh-five 294K miles
    1962 Scout 80 parts I guess
    1966 Scout 800 resto job
    2005 Chevy 2500HD Short cab long box DURAMAX
    1996 P30, 6.5 NA Mac Mobile
    whole lot of buicks

  10. #10
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    I have considered ditching the TBI, but everything is computer controlled. If I decided to ditch it and go carb, I'd have to mod the transmission and the brakes (anti-lock). So I'd like to be able to keep the computer and the TBI unfortunately.
    Ryan
    95 Chevy K1500 Z71 Extended Cab
    383 Stroker, 400 HP, 485 Ft-Lbs Torque

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