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Thread: TBI bogs at half throttle or more

  1. #1
    Carb and Points!
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    TBI bogs at half throttle or more

    I have a fresh built 355. It has a melling mtc1 cam, shorty headers, egr deleted. I also have a chip from Harris Performance. It only has a few hours on it including cam break in. It runs great when taking it easy on the throttle. I've even had it up to 70 and in 5th/OD. if I try to get into the throttle too much though it bogs, it's still trying to rev and does slowly but seems like it is starving for gas. From what I've read this weekend online it seems that I need to put an ep381 fuel pump in it and replace the regulator spring to up the pressure. I Just honestly don't know if that's the problem or not. Any help would be appreciated. Also my timing is set to 0. Should I maybe advance it a couple of degrees and see if that helps. I keep hearing about pinging. I have no idea what pinging sounds like. Plus my exhaust is so loud and the fan is loud. I'm not sure I could hear pinging if I knew what it did sound like.
    Last edited by JMiller3; 06-12-2017 at 06:05 PM.

  2. #2
    Fuel Injected!
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    I assume you have the equipment to datalog?

  3. #3
    Carb and Points!
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    Negative. I notice that seems to be what everyone talks about on here. I wouldn't know how to catalog if I did have the equipment, and it's a k150p extended cab. I'm just hoping someone on here can tell me whether they agree or not that the high output fuel pump and a higher pressure regulator spring would solve the problem. And if they do agree maybe the know which spring I should run for the cam I have with stock heads etc.

  4. #4
    Carb and Points!
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    Datalog*

  5. #5
    Fuel Injected!
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    The fuel pump could help if in fact your running lean along with an adjustable fuel pressure regulator. For the regulator you can make your stock one adjustable... https://www.thirdgen.org/tbi-afpr/ Take a look at the link, I can find others as well if this one isnt clear. To really know whats going on you need to be able to datalog. Then youll know for sure whats happening. The cables are cheap and the Tunerpro software is free, though a donation is welcome. For a cable check out Moates.net. or http://www.aldlcable.com/products/aldlobd1u.asp.

  6. #6
    Super Moderator dave w's Avatar
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    Quote Originally Posted by JMiller3 View Post
    Negative. I notice that seems to be what everyone talks about on here. I wouldn't know how to catalog if I did have the equipment, and it's a k150p extended cab. I'm just hoping someone on here can tell me whether they agree or not that the high output fuel pump and a higher pressure regulator spring would solve the problem. And if they do agree maybe the know which spring I should run for the cam I have with stock heads etc.
    Bogs can occur with to much fuel or not enough fuel. If you could post more about what was happening with your engine, see attached screens shots, I would have suggestions on what to try next.


    dave w
    Attached Images Attached Images

  7. #7
    Carb and Points!
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    Thanks

  8. #8
    Fuel Injected! MAC's Avatar
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    Subscribed. Looking forward to learning more here. I had these problems when I first started tuning my truck a month ago - turned out to be timing. JMiller - what heads do you have on your truck?

  9. #9
    Carb and Points!
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    Stock swirl port heads. My timing is good. I've checked it multiple time, also have tried adv/ret 2 degrees at a time with no good results. I was driving it two days ago and have almost made up in my min that it's the fuel pump. I'm pretty sure it died other day. Lol. Could be the coil too I guess. I have a new coil I'm putting in in a few hours so we will know then.

  10. #10
    Super Moderator dave w's Avatar
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    It might be a coil or it might be the fuel pump? If we knew what was happening with the Injectors and Spark Advance (see screen shot), we might be able to better figure things out? Air Fuel Ratio's (AFR's), see attached screen shot, would be nice to know also! It might be a failed or failing part or maybe the Chip Programming needs some corrections?

    dave w
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  11. #11
    Fuel Injected!
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    Quote Originally Posted by JMiller3 View Post
    I also have a chip from Harris Performance. It only has a few hours on it including cam break in.
    This doesn't always work out very well.

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