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Random stall at decelleration and other related(?) ills 850 1996

My 850 GLT Wagon, 5 speed, conventionally aspirated, with about 135,000mi has developed a random bad habit. It sometimes stalls at idle, more often when you pull to a stop, seldom at speed since normally one puts the car in gear and engages the clutch. Occasionally, sitting at idle, the rpm becomes unstable, revs and drops below normal, very occasionally this 'hunting' will result in a stall. Once, only once, the car stalled at a light, was hard to restart, commenced to run very badly with no power and lots of backfiring and a bad exhaust smell; this time, the car would idle; when I checked under the hood the exhaust was cherry red and the surrounding insulation was smoking hot; three hours later, having had the car transported to the dealer, it ran perfectly (and for a month afterwards!). Once, recently, the car 'stuttered' under load; no repeat, no stall.

The car has been repeatedly checked at the Wynn dealership near Philly. It has never shown the 'check engine light', nor any codes. They cleaned the throttle body but no change was noted, either in the occasional rough idle or in the random stalls at a stop.

Any ideas?








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    Random stall at decelleration and other related(?) ills 850 1996

    Red hot exhaust...
    This would typically indicate either an aspiration or an exhaust problem.
    "No flow = no go". I like the idea of checking your vacuum hoses, but if intake is not the problem, you may have a failing exhaust system. Rotted out
    baffles in your muffler are hard to detect since at lower pressure (idle) they can "drop" inside the muffler, restricting the flow, but at higher rpm can "lift" allowing flow-thru.
    Same can occur with the catalytic core.
    Good luck!
    Armie
    --
    '94 850 154000kms '86 760GLE 272000kms








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    Random stall at decelleration and other related(?) ills 850 1996

    check for any vaccum leaks, one that is a real problem is behind the power steering pump on the intake manifold, or possibly even the throttle switch.
    I would tend to go towards the throttle plate seeing as it is stalling, and if that is not the case you should check the fuel pump.








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    Random stall at decelleration and other related(?) ills 850 1996

    Might be as simple as path of spark to plugs shorting out.

    At night lift hood and see if any spark traveling anywhere on outside of plug wires (in the dark you might see a spack arc to ground, ie any metal engine part). I would advise against touching wires to avoid possible shock.

    I also had a rotor with a small crack that acted like that until it finally cracked enough to fail. Also distributor cap might be cracked.

    I also had a car that developed a small crack in the air intake hose between sensor and throttle body that only showed when engine 'flexed' the right way during shifting.

    A few ideas - good luck!







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