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TBI running rich

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by BayouBlazer88, Jan 9, 2005.

  1. BayouBlazer88

    BayouBlazer88 1/2 ton status

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    Yesterday I finally went in and retightened all my roller rockers after putting it off for quite some time because they had developed an annoyingly loud clicking. I did it the right way (the way most of the cam companies recommend, EOIC method) and pulled out all the spark plugs to make it easier to turn the crank. And when I pulled them out I noticed that they all had a good bit of carbon buildup on them (which would explain the poor idle I have been experiencing lately). But keep in mind this motor is a completely rebuilt and bored 355 with maybe 15k miles and a year and a half of use. I cleaned all of them off real good with a small wire brush and after firing it up after reassembly you could tell a big difference in the idle quality.

    Now this motor is a 355tbi with Edelbrock TES headers, TB and injector spacer, and Turbo City enlarged bore TB that I put Vortec heads on as well as the corresponding GMPP vortec-tbi intake. And if any of you have used this head and manifold combination you know what I'm talking about when I say that connecting the EGR to this is a huge PITA, hence I do not have it connected yet. I currently just have a bolt plugging up the external EGR port on the manifold. Could my lack of a working EGR system be causing the motor to run rich? Also, I have the base timing advanced about 4 degrees and I'm still using the stock computer chip. Any ideas?
     
  2. 88sub4x4

    88sub4x4 1/2 ton status

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    From my experience with these trucks an improperly working/stuck close/missing EGR will cause a lean condition. Not sure about the turbo city enlarged TB so I can't help you there.

    Did you notice any power difference with the vortec heads and GMPP intake. I have been thinking about this setup.
     
  3. Thunder

    Thunder 3/4 ton status

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    Are you sure the motor is running rich? Maby your plugs are too cold.

    Before you do anything you should hook it up to a scanner and check the air to fuel ratio.
     
  4. BayouBlazer88

    BayouBlazer88 1/2 ton status

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    First off, just to be sure, carbon buildup on the plugs and combustion chamber indicates a rich running condition, right?

    Anyway, I really cant say whether or not I've noticed a power increase because I have yet to get the motor running at its prime (EGR has never been connected, custom chip needs to be put in, etc.) but from what I've heard you can expect around 25-30 bolt-on HP from vortecs. However, after installing them I wouldn't recommend them due to the mods required and poor design of the GMPP vortec intake (ports missing, brackets dont fit right) which is your only option if you want to retain tbi with the vortecs. I wish I'd have gone with the World S/R Torquer heads instead and maybe an edelbrock performer tbi manifold which would have been a lot easier to install (heads have internal EGR ports, all vacuum ports are there, and all brackets fit correctly). So if I could do it all over again, I'd pass on the Vortecs. Good power but bad installation.

    I don't know where I can borrow or rent an OBD1 scanner because I'm definitely not pay the $300 to buy one. Does Autozone or Oreilly loan those out? Any other suggestions for getting a live scan of the air/fuel ratio? And what do you mean by "cold plugs"? I'm definitely not using any type of capacitive spark box like an MSD box, if thats what you mean, but I plan to put one on soon.
     
  5. dyeager535

    dyeager535 1 ton status Premium Member

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    winaldl will work as a scanner, if you have a laptop.

    Info all over the web on winaldl and making the cable for it.
     
  6. Mastiff

    Mastiff 1/2 ton status Premium Member

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    I think a plugged EGR would make you go lean. When the EGR is on, non-combustibe exhaust gas displaces some air and the computer will put in less fuel, only enough to go along with the fresh air. If the EGR is plugged, then it actually does get all good air, but still less fuel. The computer should compensate for this in closed loop though.

    HTH
     
  7. Stoopalini

    Stoopalini 1/2 ton status

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    Scan it with WinALDL and find out for sure what's going on. I use to use WinALDL on my '92 TBI Camaro, and it's a great little program!

    A rich condition on a TBI can be caused from a faulty O2 sensor, a leak in the exhaust before the O2 sensor's location, or an intake vacuum leak (are you sure the bolt blocking the EGR port off is air tight?)

    If all that checks out, maybe it's just going to run rich until you get a chip programmed due to the combo you used?

    Good luck,
    Thomas.
     
    Last edited: Jan 12, 2005
  8. southernspeed

    southernspeed 1/2 ton status GMOTM Winner

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    No! If you're talking about a black sooty build up then yes, it's running rich.
    If it's a brown/tan lumpy carbon build up then you're burning oil. Not so much that they're fouling and coming out greasey but oil non the less.
    If it is an oil carbon deposit it would probebly mean it was not bored/honed too well or not run in properly.
    There's a real conflict of interests when it comes to starting a fresh motor for the first time if it has a new cam in it. The bores want it nice and slow and easy to 'bed in' and not overheat/pick up on the skirts, the cam wants it straight up 2000rpm+ for half a ***hour!
    I've got to run mine for the first time soon and am not looking forward to it! I got away with it last time and all was well but a friend didn't want to run his big block that fast and ended up wrecking the cam straight away!
     

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