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Manifold Pressure and Code 32 EGR

Discussion in 'The Injection Section' started by Cricket, Feb 14, 2007.

  1. Cricket

    Cricket 3/4 ton status

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    For the first time in a year I took a 50 mile drive without throwing a code 32.

    If you kept up with my TBI code 32 problem you know that I couldn't diagnose it and neither could several mechanics. This is a swap on a 77 K10, all components were used with no shortcuts in the engine bay.

    A few days back I was tracing the source of a intermittant code 44 - lean O2. While dinking around I found that my throttle body was loose. I fixed that problem and thought I had rid myself of the code 44. The next morning the 44 popped again so I went back out and checked that truck from top to bottom. I found a small fuel line leak which I fixed. I couldn't diagnose any other issues in the wiring, grounds, et. So I started the truck and just sat under the hood thinking about it. After 5 minutes of moving around checking this and that I noticed my metal brake booster line was loose at the manifold. I went ahead and tightened it up and called it a day. Today I had to run into Denver, for the 1st time since the TBI swap I did not throw a code 32 and had also eliminated the code 44.

    My theory is that the leak at the brake booster line was just enough to affect the manifold pressure and keep the egr from opening properly when the solenoid was triggered. The code 32 would only pop at cruise, usually under light pedal deceleration.

    Does anyone know if the stock GM TBI manifolds share overall pressure with the EGR circuit? Does any of what I'm saying make sense? It's a bit too coincidental for me to pass off as a fluke.
     
  2. southernspeed

    southernspeed 1/2 ton status GMOTM Winner

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    Sounds very reasable to me. You may have cracked it! Good job!
     
  3. southernspeed

    southernspeed 1/2 ton status GMOTM Winner

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    Sounds very reasable to me. You may have cracked it! Good job!
     
  4. dyeager535

    dyeager535 1 ton status Premium Member

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    MAP setups look for the pressure change when EGR is commanded on (because it's a vacuum leak) so it makes some sense that if the MAP values are already off due to a vacuum leak, the EGR being commanded on wouldn't net the values the ECM is looking for from the MAP. (pressure is expressed as voltage to the ECM)
     

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