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TBI 305 Problems!?!?

Discussion in 'The Garage' started by bluejeep, Apr 8, 2004.

  1. bluejeep

    bluejeep 1/2 ton status

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    I have an '88 TBI 305 that has recently started to run very poor. It stumbles when I hit the gas, and "falls on it's face". I thought it was a fuel problem, then an ignition problem, and now think it's an electrical problem. Here's my list of things I've replaced: fuel pump, fuel filter, rebuilt throttle body, MAP sensor, TPS, IAC, oil pressure switch, O2 sensor, distributor cap, rotor, plugs, wires, dist. is 2 years old. I've tested the fuel pressure and it's 15psi feed and 0 return. Timing is correct.

    I'm now trying to eliminate the computer as a potential problem, so my question: Can I put the computer 7747 from my pickup in it (also with 7747) and leave the 350 chip in it for diagnostic purposes, or am I going to have to put the 305 chip in the good computer?
     
  2. realsquash

    realsquash 1/2 ton status

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    U can swap the ECMs but you will need to run the 305 chip.

    Andy
     
  3. bluejeep

    bluejeep 1/2 ton status

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    OK.

    Anybody else ever had similar experiences with a TBI Chevy? It was supposed to be about the most reliable engine I could get. It is turning out to be the most headaches I have ever had.
     
  4. FWP

    FWP CRS

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    Throwing any codes? What does the spray pattern on the injectors look like? How does it idle? What's the vacuum look like?

    The ECM's are identical but the program is different on a 305 vs 350, due to the smaller injectors et al on the 305, so yeah swap chips...but the ecm usually doesn't have problems, but you never know...
     
  5. bluejeep

    bluejeep 1/2 ton status

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    Running rich is the only code. Spray pattern looks good, one of the injectors is new. It idles OK, I might ground the park/neutral wire to see if that improves it any. Not sure about the vaccuum.

    I put the different computer in it last night and changed the fuel pump relay again, and it runs pretty good. Better than it has in over a year. Been through 4 fuel pump relays in the past year. Last 2 were NAPA ones which lasted a only a few weeks.
     
  6. civicstomper

    civicstomper 1/2 ton status

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    I have had that exact same problem (not trying to hijack, just saying i have similar problems) on my 87 350TBI for several months now and it is driving me insane. If it helps at all, I replaced the fuel pump, fuel filter, fuel lines, spark plugs, wires, distributor cap and rotor, MAP, O2, TPS sensor, all new vacuum lines, and last I checked the timing was good...

    I have been talking to this guy in town who has seen this problem on Chevy TBI trucks, and he is saying that most of the time if the stuff I already did doesnt fix it, then its a bad distributor or a loose connection at the ECM.

    Another friend of mine that really knows his stuff keeps thinking that it has something to do with the temperature. He had me make a heat riser type of thing to send head up to the manifold as it didnt have one before for some reason. He thinks it might be the temperature sensor, so thats probably going to be the next thing i check

    hope that helps, if you figure it out please pm me or something if u dont mind, I really want to get this fixed. Good luck!

    -pete /forums/images/graemlins/k5.gif /forums/images/graemlins/truck.gif /forums/images/graemlins/usaflag.gif
     
  7. ilikemud

    ilikemud 1/2 ton status

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    i dont know if i am way off but my 89 tbi 350 did the same thing it ended up being a plugged cat? maybe go back and check over the small things like wire connections, burnt fusable link?
     
  8. realsquash

    realsquash 1/2 ton status

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    I'll trade you a nice Holley carb for that TBI setup, wires and all. Should be a fair trade.

    What's your initial timing set to with the EST wire unplugged?

    Andy
     
  9. Thunder

    Thunder 3/4 ton status

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    I know I sound like a broken record posting this over and over to so many posts..But...
    You should really invest in a scanner (Auto Xray $150.00). Or if you have a laptop download WINALDL For free and buy 20.00 in parts from radio shack to make a cable.
    More infohttp://www.tbichips.com/ Building cable, downloads ect.
    Scaners wont tell you everything that is wrong with your rig but they will tell you what is right so you dont go needlesly replacing good parts. They give you an Idea exactly what the ECM is seeing from the various sensors.
    A scanner will save you a LOT of time, money,and frustraition.IMO If you have FI and want to keep it running right they are pretty much a nessisity.
     
  10. bluejeep

    bluejeep 1/2 ton status

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    No cat, that's not it. About the only sensor I did not replace is the Coolant temp sensor.

    More info on the WINALDL please. I thought that was only for modifying the chip, I wasn't aware there were diagnostic features with that. I WOULD be interested in purchasing a laptop and the cable if I could get some good diagnostic software to troubleshoot the TBI.
     

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