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Disabling EGR system?

Discussion in 'The Garage' started by bornreadyk5, Nov 27, 2005.

  1. bornreadyk5

    bornreadyk5 Registered Member

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    I have a true duel exhaust system on my 89 K5, 350 TBI. It is 2 1/2in. pipe into some cheapy Raptor mufflers. My problem is after driving about 10 miles, my SES light comes on. Its a EGR code that is triggered from insufficent back pressure resulting from the Duel exhaust.

    Anyone have a procedure to "fool" the ECM to prevent the SES light from coming on?

    I dont really want to remove the EGR, just trick evrything into working ok and not trip the SES. Thanks for you help in advance.
     
  2. southernspeed

    southernspeed 1/2 ton status GMOTM Winner

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    Are you sure why that's triggering? I have a very free flowing 3" system on mine 2:1 with a Borla Sportsman muffler with no troubles.
    I could be wrong but I think you need to look elsewhere for your trouble.
    If Mr. Yeager doesn't step in with some sound advice take a look at the boards over on thirdgen.org.
    Good luck.
     
  3. neverendingproject

    neverendingproject 1/2 ton status

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    I have true duals with only hollowed out glass packs and ive never heard of that. try the vaccum switch thing that controls the egr diaphram
     
  4. bablazer73

    bablazer73 1/2 ton status

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    you might look for other problems. I have true duals with High flow cats and flowmasters on my wifes 89. No problems with it.
     
  5. bornreadyk5

    bornreadyk5 Registered Member

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    Thanks for the replys...I really appreciate them.

    I'm not ruling out other problems, But I do know it started immediately after the exhaust was installed. I also had a previous 88 gm truck do the same thing after removing the kitty.( no emission testing here)

    Also, On both vehicals, same situation, I plugged my snap-on MT2500 scanner to see what the code was. Both Vehicals had the same code, IIRC a code 32.......and in the troubleshooting section of the scanner it stated that a possible code setting condition would be a aftermarket exhaust creating a reduced backpressure thus not letting the EGR function properly.

    Now what exhaust backpressure has to do with EGR function....you got me. I cant think that hard.

    I am 99.9% sure this is the problem, I just need to find out how to "trick" it so the SES light quits buggin me. The truck runs fine, and short trips are not affected. It seems to only come on after a 10 mile drive. It goes off when you turn off the engine and remains off until next 10 mile trip.

    I am wondering if a block off plate sandwiched between the EGR and intake will do the trick? Any thoughts?
     
  6. bornreadyk5

    bornreadyk5 Registered Member

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    Its worth looking into to. Thanks. I'll keep ya posted.
     
  7. az ranger

    az ranger 1/2 ton status

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    mine does the same thing. I have single 3" with no cat and a flowmaster

    Usually mine will not come on until I drive for half hour or more but it also gives me the egr code
     
  8. bornreadyk5

    bornreadyk5 Registered Member

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    You Homo! whats up? Did it start doing it after the exhaust? i'll get to the bottom of it and let you in on it. :haha: Until then, there may be a chance our EGR solenoids may be burnt. But I dont know, to much of a coincedence. It happens evrytime I modify the exhaust on a TBI vehical. Maybe a blockoff plate will work. If I dont get anymore Ideas here, we'll just hafta expeirment. Peace.
     
  9. Cornfield creations

    Cornfield creations 1/2 ton status

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    Probably if there is any sort of change in backpressure it will trip it. Should have .5 pounds of backpressure up to 1.0. Drill a hole, tap it and put a gauge in there. If the needle bounces then it may be an engine running problem, if it's a steady needle over 1.0 then you have too much backpressure. Most exhaust shops do it as a service if you do not have a gauge to try it. We usually charge about $35 to do a backpressure test.

    Just a thought....
     
  10. bornreadyk5

    bornreadyk5 Registered Member

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    And if the backpressure is insufficent...then what? What kinda engine problems are you talking about?
     
  11. az ranger

    az ranger 1/2 ton status

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    yes after cat came off it started with the egr code
     
  12. Cornfield creations

    Cornfield creations 1/2 ton status

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    I am unsure if too little of backpressure would cause a problem or not. I meant if the needle is not steady, and it boucnes around while holding a steady RPM then there might be an engine problem, maybe an occasional miss.
     
  13. dyeager535

    dyeager535 1 ton status Premium Member

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    Some thirdgen searching is probably in order, although I've not seen mention of the problems you are mentioning.

    Some years TPI used an EGR temp sensor to make sure that when the solenoid was commanded, the temperature in the EGR path changed indicating hot exhaust was passing through it.

    I'd bet the more primitive (sorry, couldn't help myself :)) early TBI uses no such sensor, and instead watches to see what happens to the O2 sensor reading when the EGR solenoid is commanded. If the mixture doesn't go lean, it will trigger the SES. EGR parameters are pretty narrow (temp, engine vacuum, time at certain speed, etc) so that's why the relatively long time before seeing a code.

    I see how EGR could be affected by this, it just seems unlikely, but possible I guess...EGR port(s) are open to the intake when the valve opens, which means intake vacuum should pull the exhaust gas into the intake, unless there simply isn't enough reaching the exhaust crossover where EGR is taken from with TBI. How that would be possible I'm at a loss...all there is in exhaust IS exhaust!

    Turning the light off would mean burning a new chip if lack of exhaust gas is the cause.
     
  14. dyeager535

    dyeager535 1 ton status Premium Member

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