Hello, Allpar Forums member or visitor! If you were a member, you would not see this ad!

Register or log in at the top right of the page...

  1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.

Truck pinging on acceleration

Discussion in 'Dakota, 1998-2013 Durango and Aspen' started by Peymack91, Sep 10, 2016.

  1. RalphP

    Level 2 Supporter

    Joined:
    Aug 26, 2014
    Messages:
    94
    Likes:
    32
    Always, with the caveat that fully warmed up, in neutral, no A/C, it may be backed off all the way.

    RwP
     
    Peymack91 likes this.
  2. NYBo

    Level III Supporter

    Joined:
    Jan 3, 2005
    Messages:
    4,133
    Likes:
    92
    IAC is always "active" when the engine is running.
     
    Peymack91 likes this.
  3. Bob Lincoln

    Bob Lincoln "CHECK FAULT CODES"
    Level 2 Supporter

    Joined:
    Jul 10, 2002
    Messages:
    29,882
    Likes:
    3,262
    The "lumpy" idle of a 3.9 V-6 is inherent in the design. It's basically a sawed-off 318 block with new crankshaft, and since the block has a 90-degree angle to it instead of 60, it will forever be slightly unbalanced.
     
    Peymack91 likes this.
  4. Peymack91

    Peymack91 Member

    Joined:
    Aug 17, 2016
    Messages:
    42
    Likes:
    0
    I think the IAC may be DOA. I will replace with one known good and see if that, combined with a new thermostat will even out the power. Will attempt timing at same time and see if it "takes".
    The IAC in my Nissan pickup was a cold start aid, but after warm-up, it served no real purpose. I never changed it out for that reason. Good to know about the IAC in the Dakota, thank you.
    I do appreciate all the responses! I really like the truck and want to see it run its best.
     
  5. Bob Lincoln

    Bob Lincoln "CHECK FAULT CODES"
    Level 2 Supporter

    Joined:
    Jul 10, 2002
    Messages:
    29,882
    Likes:
    3,262
    Why do you suspect the AIS motor?

    This motor is sensitive to the type of dist cap used. For some reason, caps with aluminum contacts in the towers will oxidize and form a white, fluffy powder, and this affects idle smoothness and power. For that reason, I always use caps that have brass contacts. NAPA carries Belden brand that works great. I also use Belden wires, and replace them every 30K miles.
     
    PCRMike likes this.
  6. Peymack91

    Peymack91 Member

    Joined:
    Aug 17, 2016
    Messages:
    42
    Likes:
    0
    I cannot see the pintle making any movement, whatsoever. It has remained at the same position from the time I bought the car.
    A new cap is waiting for me at NAPA, BTW. We think alike with the aluminum v. brass comparison.
     
  7. Bob Lincoln

    Bob Lincoln "CHECK FAULT CODES"
    Level 2 Supporter

    Joined:
    Jul 10, 2002
    Messages:
    29,882
    Likes:
    3,262
    I've never been able to see pintle movement in any car I've had. Too well embedded in the throttle body. A definitive test would be needed to suspect it.
     
  8. Meester Beeg

    Meester Beeg Active Member

    Joined:
    Sep 10, 2016
    Messages:
    140
    Likes:
    45
    The reason you can't see IAC pintle movement is because it's inside the throttle body. You can remove it and clean it but don't move the pintle.
     
  9. ImperialCrown

    Level III Supporter

    Joined:
    Jun 8, 2008
    Messages:
    18,233
    Likes:
    2,660
    If you remove the IAC from the throttle body, plug it into its connector and cycle the ign key from off to run, you should see the pintle extend and retract waiting for the start-up idle speed 'flare'.
    Don't start the engine with the IAC out, it will race with the opened air passage.
     
  10. Peymack91

    Peymack91 Member

    Joined:
    Aug 17, 2016
    Messages:
    42
    Likes:
    0
    I've mistaken one thing for another. I was under the impression that the IAC was the part that has a bolt that the throttle cables ends rest against. It struck me as odd that Dodge would use such a crude device to control idle, but what did I know?
    What does THAT device do? Is it for tuning throttle response?
     
  11. ImperialCrown

    Level III Supporter

    Joined:
    Jun 8, 2008
    Messages:
    18,233
    Likes:
    2,660
    I keep forgetting that this is a '91 with TBI. That has an external throttle control. The idle speed should still flare when first started and then settle down into a lower curb idle.
     
  12. Peymack91

    Peymack91 Member

    Joined:
    Aug 17, 2016
    Messages:
    42
    Likes:
    0
    That's what I was thinking, if it wasn't the AIC. It does flare up, then settle. It is turned all the way in though, so is there a rule of thumb about how far in that bolt should be?
     
  13. ImperialCrown

    Level III Supporter

    Joined:
    Jun 8, 2008
    Messages:
    18,233
    Likes:
    2,660
    There is a base (minimum) idle adjustment procedure in the service manual. The throttle stop screw should always be in contact with the throttle lever. The PCM controls what it wants the idle speed to be.
    Do you believe that the idle speed is too low?
     
  14. Peymack91

    Peymack91 Member

    Joined:
    Aug 17, 2016
    Messages:
    42
    Likes:
    0
    No, idle seems to be about right. It just seems that the pictures I've seen show that screw as being much further out than mine (mine is all the way in).
     
  15. Peymack91

    Peymack91 Member

    Joined:
    Aug 17, 2016
    Messages:
    42
    Likes:
    0
    OK, new (correct) thermostat produced no real change. Needle still shows about 1/3 on the gauge. That must be normal for the truck.
     
  16. Bob Lincoln

    Bob Lincoln "CHECK FAULT CODES"
    Level 2 Supporter

    Joined:
    Jul 10, 2002
    Messages:
    29,882
    Likes:
    3,262
    I bought my Dakota in 2004 from my brother, the original owner. It had a code 17 that went away when I changed the thermostat. However, it never got beyond the warm mark, which I thought was normal. Years later, mileage was off a little, and the temperature wasn't making it up to warm fast enough. A thermostat change did nothing. I then found that both the temp sending unit (1-wire) and the coolant temp sensor (2-wire), were both cracked and falling apart. They are on either side of the thermostat on the 3.9L and are easily damaged when servicing the thermostat. I replaced both, and now it reads 30-40% of scale consistently when warm. Gas mileage is normal.
     
  17. Peymack91

    Peymack91 Member

    Joined:
    Aug 17, 2016
    Messages:
    42
    Likes:
    0
    Sounds reasonable: truck is warm enough, but gauge is off for various reasons.
     

Share This Page

Loading...