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Dies When Off the Throttle

Discussion in 'Technical Chat' started by trutac, Jan 2, 2012.

  1. Jan 2, 2012 at 9:42 PM
    #1
    trutac

    trutac [OP] New Member

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    I've searched and searched and searched but still cannot find a definitive answer. I have a 96.5 Tacoma with the 3.4 and manual. I recently put in a rebuilt 3.4 after it was discovered that the compression was way low in the middle cylinders. In addition there is a new TPS, a cleaned out IAC and some other things I will list.

    The problem is that when it is cold and I let off the throttle the engine stutters bad, sometimes dying when I get off the highway. The problem (I assume to be poor fuel delivery) only seems to occur when there is deceleration or a let up on the gas pedal and when the outside temp is cold, below 50 F.

    I recently did a fuel pump after first putting in a faulty replacement fuel pump. The wires looked fine and there didn't appear to be any kinks in the line. The faulty pump wouldn't start after a long, hot soak- about 1/2 hour after the engine had warmed up. The new pump has fixed these issues.
    While this was happening I 'tried' a new MAF before I put in the new fuel pump. That MAF didn't make a difference so I returned it- this was 2 months ago so I can't rule out the MAF but I doubt that I can 'try' one out again.

    Was thinking inertia switch but there isn't one.

    Any ideas out there?
     
  2. Jan 2, 2012 at 9:52 PM
    #2
    fireturk41

    fireturk41 I like to break shit!

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    Idle Air Control under the throttle body
     
  3. Jan 3, 2012 at 9:52 AM
    #3
    BlueT

    BlueT Well-Known Member

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    Check engine Coolant temp sensor. That is what manages IAC valve. Your second bet could be vacuum leak which adds air to system behind MAF.
     
  4. Jan 3, 2012 at 1:34 PM
    #4
    trutac

    trutac [OP] New Member

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    Fireturk: I cleaned the IAC spotless and the solenoid had no issue spinning; but that doesn't necessarily rule out the solenoid, does it? Is there a way to test the solenoid other than banging on it when it is cold?

    I forgot to mention that I did put a new coolant temp sensor in the rebuilt engine given its pain-in-the-ass location under the fuel rail. I know the ECU works with the MAF and coolant temp sensor so I am back to the IAC solenoid or MAF.

    BlueT: would a vacuum leak be sensitive to a low ambient temperature?

    this only happens when it is cold....anyone know if a faulty open circuit (fuel pump) relay brings about throttle-off stuttering during cold temps?
     
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