TBI problem, Truck won't stay running

Discussion in 'Engine Performance + Maintenance' started by Darrell, Jun 12, 2019.

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  1. Darrell

    Darrell I'm Awesome

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    Hey all, I've continue to have some sort of TBI problem since it's rebuild.

    I have a '95 TBI with a couple issues.

    1) The throttle blades are sticking now (This is new) but only after it's been running then shut off and it sits for a few minutes. If I try to restart the throttle pedal won't move until it's press hard and then it frees itself and operates normal. This is only on the initial start up and only after it's sat for a while.

    2) I've replaced several sensors, TPS, IAC, Throttle body temp to be exact. I was getting the code flashes for these so I've replaced them. Fixed, I no longer get any codes flashing except the normal "1-2" flashes at the beginning.

    BUT...the problem is that once it's started (after the sticking blades free up) it won't stay running once I crack the throttle. Whether it's from inside on the pedal or under the hood at the throttle linkage.

    I'm showing approx 10-11 psi on my fuel gauge at the rear of the TBI, so that seems good..I think

    Not sure if I'm getting to much fuel and it's choking itself out or what..but once it's starts up I'm getting black smoke and black soot specs all over the driveway....

    any suggestions.....I'm about the scrap this TBI and look for an alternative replacement !

    Thanks in advance
     
  2. PlayingWithTBI

    PlayingWithTBI Desert Old Guy

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    I had a problem with my throttle sticking, it turned out that if I adjust the idle screw (blue arrow) too far out the cable catches on the sleeve connected to the linkage (red circle). HTH

    upload_2019-6-12_15-5-56.png
     
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  3. Darrell

    Darrell I'm Awesome

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    PlayingwithTBI... wow! that correct the sticking blades. I guess I didn't pay much attention to how far out I turned the screw while messing with the idle.

    Now problem 2 is still going on which is dying once the throttle is cracked :( BTW while driving it at any particular speed I can punch it and it responds. This dying only happens while at a complete stop or in park and idling. If I'm driving and stopped I have to feather the throttle to keep it from falling on it's face.
     
  4. PlayingWithTBI

    PlayingWithTBI Desert Old Guy

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    Got a scanner? Take a look at your plugs, are they fouled?
     
  5. PlayingWithTBI

    PlayingWithTBI Desert Old Guy

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    Oh yeah, how's your initial timing? Did you "tune" the PCM in particular the AE (it gives you an extra shot of fuel when you accelerate like the accelerator pump on a carb) or PE (like the power valves in a carb) tables?
     
  6. Darrell

    Darrell I'm Awesome

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    No scanner...only the a jumper wire (paper clip) to the "A" and "B" pin on the ALDL which showed no codes.

    I just started pulling the plugs to see if they had fouled and yes most all. Now I'm still confused because I had this problem before and these plugs were installed new. Now there fouled, so something is causing them to foul. I'm not a carb guy at all and I'm chasing my tail as this will be a third set of plugs....grrrrr !

    I'll replace Friday as it's getting dark and I'm working all day tomorrow..bummer

    As far tunning the PCM..No I haven't nor do I know how. The TBI does seem to be getting to much fuel, I can watch it dump into the bowls choking it out.

    Also this is a new rebuilt orig eng.
     
    Last edited: Jun 12, 2019
  7. Darrell

    Darrell I'm Awesome

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    Curious...is it possible the the fuel regulator on the back of the TBI is bad ?
     
  8. bobby v

    bobby v I'm Awesome

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    Im having some troubles with my TBI unit also, everyone says get an ALDL connector cable so that it can be attached to a laptop for a scan rea out, of course then Im lost after that.
    I just got it back today from the shop and they chased things somewhat, timing was at 12', Fuel pressure was 11.2pSI, voltage to the engines was good, ETC. I haven't drive it except to come home though so we'll see
    Bobby v
     
  9. PlayingWithTBI

    PlayingWithTBI Desert Old Guy

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    You may want to try a hotter plug and see how it runs. You still need to determine if it is running rich, a scanner or data log can tell you that. AIr fuel mixture should be ~14.7:1 (depending on your gas/alcohol ratio), your INT (Integrator), short term, and BLM (Block Learn Multiplier) long term should be ~128.

    Then when you step on it the AFR should go down according to your PCM settings.
     
  10. Darrell

    Darrell I'm Awesome

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    Is this something that I could do myself with the correct tools ? And if so could you educate me a little on what scanner or tools I would need, or does the cost of these tools needed out way one doing it themselves?

    I'm mechanically inclined as I rebuilt this engine and others, I'm just not up on the fine tuning these TBI's.
     

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