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  1. #1
    Join Date
    Jan 2005
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    West Coast USA
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    Default intermittent loss of acceleration

    I have a problem related to intermittent loss of acceleration this weekend. There are times when hitting the gas pedal, car would take awhile before the acceleration would kick in. Coincidentally or not, prior to this, I was on a dirt road and when turning around k-turn, it felt like I hit a rock on the bottom of the car. I was able to drive 90 minutes back home and reach normal speeds of 60mph, but again, had this intermittent delay of acceleration. Local mechanic looked at bottom of car on rack but did not visibly anything obvious. Thoughts, suggestions ?
    Last edited by rhauptschein; 01-04-2021 at 04:25 PM.
    09 Toyota Prius, Sprectra Blue
    01 Volvo V70XC, Ice Blue, 7-seater, built 4-01
    85 Ford Country Squire, Beige Woody, V8, ~79K mi [RIP]
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  2. #2
    Join Date
    Aug 2017
    Location
    Pleasanton CA USA
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    464

    Default

    When's the last time you put in spark plugs? How old are your coil packs? Air filter?

    When you're parked, how fast can you build RPMs? If it's got a lag, I'd be viewing traces on engine diagnostics, looking for:
    - low fuel pressure
    - lag in Mass AirFlow signal
    - lag in throttle position


    If the low acceleration only occurs when driving, it could be a problem in drivetrain. Monitor your fuel mileage for any decrease.
    2013 XC70 T6 Flamenco Red (hers)
    2015 XC70 T6 Seashell Metallic (his)
    past: 13 Volvos going back to '74 242 sedan

  3. #3
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    Jan 2005
    Location
    West Coast USA
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    311

    Default

    is loss or compromise of computer communication to the ECM possible here ?
    09 Toyota Prius, Sprectra Blue
    01 Volvo V70XC, Ice Blue, 7-seater, built 4-01
    85 Ford Country Squire, Beige Woody, V8, ~79K mi [RIP]
    70 Chevy Malibu, Forest Green, V8 (ret)

  4. #4
    Join Date
    Jan 2005
    Location
    West Coast USA
    Posts
    311

    Default

    Quote Originally Posted by pbierre View Post
    When's the last time you put in spark plugs? How old are your coil packs? Air filter?

    When you're parked, how fast can you build RPMs? If it's got a lag, I'd be viewing traces on engine diagnostics, looking for:
    - low fuel pressure
    - lag in Mass AirFlow signal
    - lag in throttle position


    If the low acceleration only occurs when driving, it could be a problem in drivetrain. Monitor your fuel mileage for any decrease.
    thanks, pbierre; do you think any, all, or none of your possibilities are related to that under the car hit I described in OP ?
    09 Toyota Prius, Sprectra Blue
    01 Volvo V70XC, Ice Blue, 7-seater, built 4-01
    85 Ford Country Squire, Beige Woody, V8, ~79K mi [RIP]
    70 Chevy Malibu, Forest Green, V8 (ret)

  5. #5
    Join Date
    Jan 2012
    Location
    SF Bay Area, Cali
    Posts
    16

    Default

    Fuel line or fuel filter come to mind when I hear about things under the car getting hit and it resulting in engine hesitation.

  6. #6
    Join Date
    Aug 2017
    Location
    Pleasanton CA USA
    Posts
    464

    Default

    Quote Originally Posted by rhauptschein View Post
    thanks, pbierre; do you think any, all, or none of your possibilities are related to that under the car hit I described in OP ?
    How does the engine do in P or N? racing up the RPMs....any lag?

    There's a possibility that the rock hit the drive train (angle gear, prop shaft, Haldex-rear-differential) and put it out of alignment. That's why I suggested evaluating the engine response
    while parked in P, and if it's good, monitoring fuel mileage. If the drive-train got banged up/misaligned, you should be seeing a loss of gas mileage.

    Another way to evaluate drive train is to put her in neutral (engine off), and jack up either rear wheel, then rotate it manually. It should turn without much resistance and no squeals/grinding. Then, evaluate the other rear wheel the same way.

    If you think the front-end got whacked, do the same wheel-resistance tests on the fronts ( in N).
    Last edited by pbierre; 01-11-2021 at 03:31 PM.
    2013 XC70 T6 Flamenco Red (hers)
    2015 XC70 T6 Seashell Metallic (his)
    past: 13 Volvos going back to '74 242 sedan

  7. #7
    Join Date
    Aug 2017
    Location
    Pleasanton CA USA
    Posts
    464

    Default

    Quote Originally Posted by rhauptschein View Post
    is loss or compromise of computer communication to the ECM possible here ?
    Those are detected and reported at the dashboard console with a Check Engine alert.
    2013 XC70 T6 Flamenco Red (hers)
    2015 XC70 T6 Seashell Metallic (his)
    past: 13 Volvos going back to '74 242 sedan

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