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1999 Xc70 Smooth Idle, Lumpy Up-hill Cold Acceleration V70-XC70 1999

posted by  jokomoto on  Sun Feb 10 16:04 CST 2008
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last visit: Thu Feb 21 18:53 CST 2008
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Strange combination. I swapped out plugs, (went with coppers), checked my coil packs, and am stumped. The lumpy-ness seems to lessen as the car warms up, but is still there. Really bad when cold. No codes. My MPG is also not good, 14mpg. I live in hilly Seattle, but I think this problem is causing my poor MPG.

It feels mechanical. Could it be something like a burnt valve, a PCV problem, exhaust manifold leak?

Any Ideas?








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    1999 Xc70 Smooth Idle, Lumpy Up-hill Cold Acceleration V70-XC70 1999

    posted by  uncletom on  Mon Feb 11 07:33 CST 2008
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    last visit: Tue Feb 12 19:24 CST 2008
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    Sounds like the same symptoms of my 99 S80. Turned out to be a vacuum leak on the brake booster on the pedal side. Needed new booster to remedy. Dealer in Bellingham did not think this could cause the symptoms but turned out to be the only problem, no lights or codes. Any vacuum leak or air to the engine without passing by the Mass Air Flow Meter will upset the computer controlled fuel system.
    You might try clamping off the hose to the Booster and see if this helps. No power brakes during test obviously. Tom







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