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TBI Question

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Brad79, Nov 20, 2002.

  1. Brad79

    Brad79 Registered Member

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    I have recently swapped a 1991 350 TBI setup onto my 79, which has a 383, with 64cc Dart Iron Eagle heads, a pretty much stock cam, and about a 10.1:1 compression ratio. I am having some problems getting the TBI setup to run correctly. It will idle ok..not great, but ok. But when I accelerate it spits and sputters and backfires on me, but if I floor it, it seems to be ok. It almost acts like it is fuel starved, but I read a fuel pressure of 14 psi. So my question is...would I benifit any with a new chip for the ecm? I can't really think of anything else it could be. /forums/images/graemlins/1zhelp.gif
    Thanks
    Brad
     
  2. jc71355

    jc71355 1/2 ton status

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    Are you getting any codes?
     
  3. fortcollinsram

    fortcollinsram 1/2 ton status

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    YES...the 7747 ecm is barely enoguh for a mild 350 let alone a 383...Call some of the chip mfg's and see what they say...I'm sure somebody else can tune in with a specific mfg of custom chips...

    Chris
     
  4. HarryH3

    HarryH3 1 ton status Author

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    One of the car magazines put TBI on a hot 383 a while back. I think the folks at www.turbocity.com were the ones that helped them get it running correctly. /forums/images/graemlins/cool.gif
     
  5. Kyle89K5

    Kyle89K5 1/2 ton status

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    Contact this guy. Tell him your specs and see what he's got to say. Custom EFIS

    Trust me, he know's his stuff.

    KP
     
  6. Brad79

    Brad79 Registered Member

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    Great...thanks for the help guys...I'll give e'm a call and see what they say. /forums/images/graemlins/thumb.gif
     
  7. BurbinOR

    BurbinOR 3/4 ton status

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    Kyle and Harry have given you a couple of good options. Here's another one - www.fastchips.com - Ed Wright is highly respected over at www.thirdgen.org for his ability to burn chips right the first time.

    Since you are now a FI guy - I'd highly recommend you get either a scanner (like one from www.autoxray.com ) or check out this site Craig Moates FREE software, which requires you to build your own cable interface to the ALDL (no big deal, some guys are selling them too), or there is also winaldl available.

    The problem is not the 7747 computer, it is the chip that has all the fuel maps, advance curves, etc.

    That scanner or equivalent is a must have for anyone running FI for setting your TPS correctly, reading if your O2 sensor is going into closed loop, if the manifold air temp (do they use that with TBI?) is working, if your IAC (Idle air control) is set right (which sounds like it could be part of your problem ). Without a scanner, you are flying blind, and codes are often times not set when you have drivability problems.

    I also recommend you start reading the boards at www.thirdgen.org - lots of knowledgeable FI guys over there.

    /forums/images/graemlins/usaflag.gif
     
  8. jmd

    jmd Registered Member

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    Just an opinion from trying out TBI on a 454, and TPI on modded motors - if you're backfiring and sputtering, you need more things fixed than just the prom.

    Matthew
     
  9. Kyle89K5

    Kyle89K5 1/2 ton status

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    FYI, If you have a laptop, follow BlazzinOR's advice and download this program and make your own cable. I did and it was a TON of help when I was troubleshooting my setup. The guy at Custom EFIS and the folks over at thirdgen.org can use this data to help to diagnose problems.

    It's a quick download and the patch cable took me and some guys I work with about an hour to make with $2 worth of stuff from the electronics store.

    Good luck and I hope it works for you.

    KP
     
  10. Brad79

    Brad79 Registered Member

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    Thanks for the advice guys, but I've actually already scanned it with a Tech1 scanner. No codes, and everything seems to be functioning correctly.
     
  11. Kyle89K5

    Kyle89K5 1/2 ton status

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    I don't know what a Tech1 scanner is, but if it's just a code reader, then you aren't getting enough info. The WinALDL program is a full on diagnostic system that reads the data from the computer for ALL operating systems. The nice thing about it, is that you can scan the truck with it while driving at YOUR convenience, instead of a shops. You'll need to make sure that you are getting good data while the truck is being driven. This will give you good load data as well as the varrying driving conditions.

    Be careful not to run the truck rich for too long, it will tear stuff up. TRUST ME.
     
  12. Chris Demartini

    Chris Demartini 1/2 ton status

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    <font color="blue">Tech1 is the scanner at the GM dealers
     
  13. Kyle89K5

    Kyle89K5 1/2 ton status

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    Is it the big mother of all scanners that cost more than my house?

    If so.... I WANT ONE!!!

    How you interpalate the data determines alot. Everything on my truck was functioning fine, but the numbers they were sending were UGLY!!! No intake vacuum. When I first hooked WinALDL up, I thought it would fix it, didn't know I'd have to sift through 5 pages of Data to find the problem. /forums/images/graemlins/eek.gif

    I love FI when it works /forums/images/graemlins/grin.gif. I'm a little balder after it didn't. /forums/images/graemlins/eek.gif

    KP
     

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