Idle problem

Discussion in 'All Topics, Chips, and Tech for Buicks' started by Dastud, Nov 10, 2018.

  1. Dastud

    Dastud Member

    87 Buick, 42# injectors, 5.7 chip #9067. Car starts and idles fine. All adjustments are where they need to be. When I put it in drive or reverse, the IAC counts start to climb and I have to push the brake hard to hold it. Put it back in park/neutral and it revs up to about 1300 rpm and settles back down to idle. In testing I removed the trans linkage that operates the P/N switch to see if was because the ecm saw drive. I removed all vacuum sources from the block too. Those did not help. Any ideas? Thanks!!

    Todd
     
    Last edited: Nov 10, 2018
  2. EricM

    EricM Administrator Staff Member

    What is the RPM just before and after you put it into drive? Is this only when cold?
     
  3. Dastud

    Dastud Member

    Any temperature. Warm idle around 750. In drive it goes to around 1000. going into neural it will flair to 1300-1400 and settle back down to 750ish.
     
  4. EricM

    EricM Administrator Staff Member

    Any way you could take a video of it happening? Mainly your scantool numbers after shifting into drive. I've never seen the idle speed go up after shifting to drive.
     
  5. Dastud

    Dastud Member

    Last edited: Nov 17, 2018
  6. Dastud

    Dastud Member

    What I notice is that when put into drive, the LV8 and the IAC counts go up. Is there a table that ties those 2 together?
     
  7. EricM

    EricM Administrator Staff Member

    The IAC should go up when shifting to drive. That's how it maintains the idle speed.

    It looks like its operating normally. Your idle rpm in park was about 825, then when you shifted to drive it dropped to about 775-800. When you shift back to park, it's common for it to flare up a little then drop down.

    If it's pulling hard on the brakes at only 800rpm, then either something is wrong with the brakes, or your torque converter stall speed is really low.

    Was that your only issue, that it is pulling on the brakes?
     
  8. Dastud

    Dastud Member

    the car wants to take off when in drive. Will do 15+ mph at the high idle it goes to. Is it normal to flare up to 1300 rpm when shifted back to neutral? I had one of these cars back in 88 and it sure didn't idle like this one. The IAC goes from 16 to 52 instantly when put into drive then climbs. Is that normal? I'm asking because I don't know. The converter is not the correct D5. It is probably tighter, guessing 1800 stall (but not sure). Could that cause all this?
     
    Last edited: Nov 17, 2018
  9. Dastud

    Dastud Member

    Another thought. I'm aware that the idle goes up in drive, that is why I i disconnected the P/N switch so the ecm could not sense it going into drive. The IAC counts went up as shown with it disconnected. What told the ecm to increase the idle? Idle drop? I'm guessing LV8. That's why i'm wondering about the correlation of IAC with LV8.
     
  10. EricM

    EricM Administrator Staff Member

    The IAC goes up based on idle rpm error. The commanded idle is 800rpm in drive. When you shift to drive, the rpm dropped to about 750 or so, which is lower than commanded, and the IAC raises up to get back to 800rpm. It's operating like it should.

    The problem is most likely the non-stock torque converter. If the stall speed is lower than stock, it is too tight, so the IAC has to climb higher than normal to maintain the 800rpm idle speed.

    Another option, to compensate for the lower than typical stall speed, is we can reprogram the chip for a lower idle speed, like 700 or so, so it's not loading against the converter like that.
     
  11. Dastud

    Dastud Member

    Makes sense, Eric. I was being cheap when I had the transmission rebuilt. I have been kicking around changing the converter. I will install a ~2500 stall lockup in it and see what that does. I know the performance will improve (launch wise). Thanks so much for your help!! Just curious, I want the converter to lock in 2nd+ at WOT. Is that how the chip is programmed?
     
    Last edited: Nov 17, 2018
  12. EricM

    EricM Administrator Staff Member

    Yes, it looks like there was a special request on that chip to lock as soon as 2nd gear hits at WOT.
     
  13. Dastud

    Dastud Member

    Would lowering the commanded idle be a problem even with the correct converter? If not I would like to change it to the lowest you think reasonable, even below 700. It would allow me to drive it prior to converter replacement.
     
  14. Dastud

    Dastud Member

    Just read your article on Idle Speed Control. Very interesting. Looks like I'm going to have to finally learn how to use this darned AutoProm after all.
     
  15. EricM

    EricM Administrator Staff Member

    We could probably get it down around 700. The chip would need to be reprogrammed.

    If you're talking about the moates autoprom, just realize you can only use that starting with a stock chip program, not one of my chips, as the programming is completely different in my chip.
     
  16. Dastud

    Dastud Member

    I will have it reprogrammed then. Would these figures work for the idle? I only drive the car in warm weather and am not concerned with idle smoothness. I prefer a lower idle as long as it will work. I changed my mind and plan on keeping the converter that is in it now. Also, is the High Negative Error/Rate Gain at zero? If not, would eliminating the high gain be beneficial? Thanks!!!
     

    Attached Files:

    Last edited: Nov 25, 2018
  17. EricM

    EricM Administrator Staff Member

    You may have stalling with those settings. I would likely bring everything down more evenly. The high neg gain is disabled.
     
  18. Dastud

    Dastud Member

    I am ordering a new chip. Please apply these new values. If they don't work, will try it again. Thanks for all the help Eric!!!
     

    Attached Files:

  19. Dastud

    Dastud Member

    Order 15840. Please ensure the lock up feature remains. Thanks!!!
     
  20. Dastud

    Dastud Member

    I LOVE THIS NEW CHIP! Starts, idles, pulls down in drive and does not run off now! Went 10% lean idle on translator. Seemed to smooth out. THANKS!!!!!!!
     

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