740GL symptoms: Rough Idle & Stall while cold

Discussion in 'Volvo 740' started by JayR, Feb 28, 2006.

  1. JayR

    JayR Guest

    1990 740GL, 180K miles.

    Starts up great, but while the engine is cold the idle is rough, and
    without a tap or light pressure on the gas pedal, the car sputters down
    and stalls. After she gets fully hot (seems to be about 10 minutes),
    the problem disappears and the idle is fine.

    I was thinking maybe dirty throttle bodies, but it seems if that was the
    cause the problem would not disappear when the car is hot.

    Could these symptom point to a dead or dying AMM? Where is that part
    located? Reading here suggests the culprit could also be the Radio
    Suppression relay? I replaced the O2 sensor not too long ago, so I'm
    ruling that out.

    Any ideas? Thanks in advance,
    Jay R.
     
    JayR, Feb 28, 2006
    #1
  2. You had it right the first time - classic for throttle body glop, including
    the lack of problem when warm... I don't know why. Especially clean the
    passage at the bottom that goes from each side of the throttle butterfly to
    the knurled idle adjustment screw. I count the turns as I screw the idle
    adjuster in, then remove the screw for cleaning and reinstall it and set it
    the same number of turns from closed.

    The Idle Air Control valve under the throttle body also needs cleaning at
    the same time. Expect to use half a can or more carb cleaner for the pair of
    them, and you should be good for a couple of years.
     
    Michael Pardee, Mar 1, 2006
    #2
  3. JayR

    User Guest

    Old plugs, bad wires, restricted injectors, vacuum leak, what have you
    checked? What codes sre present that aren't triggering the light?

    Bob
     
    User, Mar 1, 2006
    #3
  4. JayR

    mar Guest

    Sorry, posted before checking. I haven't had a free weekend in a while
    to even pop the hood, so the car keeps getting gradually worse. I
    wanted to get a list of all the possible things it could be based on the
    symptoms, gather the parts this week, and then tackle repairs in order
    of likelihood this weekend.

    Hopefully it'll be the throttle bodies like Michael Pardee suspects --
    but I appreciate your other suggestion and will check into those areas, too.
     
    mar, Mar 1, 2006
    #4
  5. JayR

    mar Guest

    Michael,

    Thanks for these tips. I cleaned the TB today and it fixed my idle
    problem. I was amazed at how stubborn a lot of those deposits were.
    Took several applications of cleaner and lots of scrubbing with the
    toothbrush to get them off. This was the first time I'd ever cleaned
    the TB, and I've owned the car from 60K to 180K. I think it's a good
    bet it's the first time it's ever been done.

    Also replaced the crank position sensor while I had the hood up.
    Hopefully this will cure my hot-start problem.
     
    mar, Mar 5, 2006
    #5
  6. maybe glug causing the throttle body to stick ,when warm it would release
    easier .Clean the electronic idle control too it gums up easy .
     
    Jon Robertson, Mar 9, 2006
    #6
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