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Need help diagnosing driveability probs on a TBI 350...

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by fortcollinsram, Feb 20, 2003.

  1. fortcollinsram

    fortcollinsram 1/2 ton status

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    First, a rundown of the symptoms and what I have replaced already...

    When I start my truck, I always trun the ingnition on and wait for the fuel pump to build up pressure...In the morning or after it has been sitting for ore than a few hours, it has to crank over for a good 4-6 seconds before it fires...And once it fires it has a really hard time keeping at idle, as it usually dies...So I have to hold my foot on the gas to about 2000rpm for about 45 seconds then it will idle fine at about 800-825 rpm. After I let it warm up for a few min. I put it in gear and take off...Wellmost of the time, it is really lurchy and when you give it gas under load, it seems like it wants to die...but this sypptom usually goes away after a few min of drving...

    If the engine is still warm, it starts fine, but still has the idleing issue, buit not as badly as if the engine is COLD...

    I also downloaded the WinALDL on my Laptop and hooked it up to the truck last night and went for a spin...The Oxygen Sensor readings are ALL over place...They varied from .9 to .004...The only time they leveld out was after the truck had been idleing for a few minutes. Once I started drving, the O2 readings went haywire...I amalso getting a lean exhaust conditoin code...

    So far, I have replace the cap, rotor, wires, plugs are in good shape, and I have run BG 44k through one tank of gas..

    Obviously I think it is something with the fuel system...My first guess would be fuel pressure regualtor, also maybe a leaky injector or somehting...

    What do you guys think...
    I appreciate any help you can lend...

    Chris /forums/images/graemlins/1zhelp.gif
     
  2. dyeager535

    dyeager535 1 ton status Premium Member

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    For the cold start crank issue, have you verified that the pump is working when it's supposed to? (2 seconds when the key goes to run) If the relay is not working correctly, the engine has to develope oil pressure before the fuel pump will start working again.

    Can't recall off the top of my head, but is the IAC position "viewable" when you scan the ECM?
     
  3. fortcollinsram

    fortcollinsram 1/2 ton status

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    Yeah, I can hear the pump run for a few seconds than hear the realy kick it off...

    Chris
     
  4. Bubba Ray Boudreaux

    Bubba Ray Boudreaux 1 ton status

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    Did ya build your ALDL cable or buy it?
     
  5. Kyle89K5

    Kyle89K5 1/2 ton status

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    You might want to consider the coolent temp sensor, it may be going bad and telling the motor it's warmer than it is or cooler than it is.

    I'm having some of the same issues on mine and I've got it narrowed down to the injectors. Once I get some money saved up, I'll get some new ones..
     
  6. Kyle89K5

    Kyle89K5 1/2 ton status

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    Almost forgot, I found that uploading the information to the thirdgen.org BBS got me lots of folks able to better interpret the data and help me narrow it down. Same goes for the guy at dyiefi.com He looked things over and helped me out a ton too.

    Just some thoughts.

    KP
     
  7. fortcollinsram

    fortcollinsram 1/2 ton status

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    I built the cable...Actually I built 2..the first one I was carrying outside to hook it up and I steped on it and ripped the legs out of the transistor...The second one is working great...easy to do if you have the patience...and its cheap...

    Chris
     
  8. fortcollinsram

    fortcollinsram 1/2 ton status

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    I will check out the thirdgen site...and I will check out the temp sender too...the ALDL program said I had an average temp of 173 degrees and that is with a 180 degree t-stat....but I replace it tomorrow anythow...Chris
     
  9. Kyle89K5

    Kyle89K5 1/2 ton status

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    They say that's one of the BIG killers and a real important sensor.

    thirdgen was a BIG help man. There's guys over their that can read that data like a Daniele Steele novel.
     
  10. fortcollinsram

    fortcollinsram 1/2 ton status

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    Tell me, do you think that a 180-degree stat is too coold...thould I throw a 190 in there for good measure?

    Chris
     
  11. Sidepipes

    Sidepipes 1/2 ton status

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    When I changed my rad, I put a 180 thermostat in it. I never liked how it ran after that.....so I went out and bought a 195 thermostat and it runs much better..... The one I pulled out of the truck was a 205 which I though t was a little high.
     
  12. MR4WD

    MR4WD 1/2 ton status

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    Is the computer controlled advance circuit hooked up? Check the plug that's beside the brake booster, make sure it's hooked up properly. Also, is the Idle Air Controller not clogged and/or working properly? The wire to the knock sensor beside the starter may also be off, but that's a long shot. I'd look first towards the computer advance.
     
  13. jjlaughner

    jjlaughner 3/4 ton status

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    One problem I'm having with rough idles is the AIR system. The tube that runs around the back of the motor from exhaust mainfold to the exhaust manifold has popped apart. I just haven't had time to get back there and fix it.
    I also found at the autopart store a Thermostat for electronicly controled motors (says GEN II) on the outside. I got the GM 195 and the truck ran alot better over the old 180 I had in it.
    What oil are you running? When I had 10w40 in, it cranked a little longer before firing, I switched back to 10w30 and it fired right up. I dont know if that would help any but its something I noticed.
     
  14. 87sm465np208

    87sm465np208 1/2 ton status

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    good greif, ther is suposed to be a air tube running around from manifold to manifold, mine is off, missing, great, now what to do?
     

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