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  1. #1
    Join Date
    Apr 2008
    Location
    Chicago (USA)
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    73

    Default Lurch While Gently Accelerating After 'Near' Stop

    While the transmission in our recently acquired 2012 XC70 T6 (with ~29,000 miles) shifts smoothly when accelerating from a dead stop, I experience a mild jolt forward when accelerating after a “near” stop.

    If I brake to slow the car down to say, 2-5 mph, as I might do in stop-and-go traffic or when driving slowly on city side streets, then gently apply the gas, the car accelerates slowly for something like one second then noticeably lurches forward accelerating at a more rapid rate despite NO change in accelerator pressure. The feeling is something like "a lag in power until something catches" or a (transmission) downshift except that there is NO change in engine RPM that I can detect.

    Has anyone experienced this?

    At a recent service visit, it was confirmed that all software updates had been applied. The service rep threw out terms like ‘torque converter’ but indicated that what I am experiencing is ‘normal’ for the car and that there was nothing to be done.

    Does this sound normal to you?

    Rich

  2. #2
    Join Date
    Nov 2009
    Location
    South Wales UK
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    1,901

    Default

    Quote Originally Posted by RichS View Post
    While the transmission in our recently acquired 2012 XC70 T6 (with ~29,000 miles) shifts smoothly when accelerating from a dead stop, I experience a mild jolt forward when accelerating after a “near” stop.

    If I brake to slow the car down to say, 2-5 mph, as I might do in stop-and-go traffic or when driving slowly on city side streets, then gently apply the gas, the car accelerates slowly for something like one second then noticeably lurches forward accelerating at a more rapid rate despite NO change in accelerator pressure. The feeling is something like "a lag in power until something catches" or a (transmission) downshift except that there is NO change in engine RPM that I can detect.

    Has anyone experienced this?

    At a recent service visit, it was confirmed that all software updates had been applied. The service rep threw out terms like ‘torque converter’ but indicated that what I am experiencing is ‘normal’ for the car and that there was nothing to be done.

    Does this sound normal to you?

    Rich
    I wondered after reading about your 'jolt' if it might be attributed to a 'problem' with the Electronic Parking Brake not backing off completely even though you have not used it.

    I was told that my rear pads wore out rather quickly due to the fact that when I pressed the brake pedal it 'charged' the rear brakes and put the pads up against the discs/rotors, so if they don't immediately back off as you accelerate again and are waiting for the 'sensor' to kick in then might this be the cause of your 'jolt'?
    Just a thought......

  3. #3
    Join Date
    Apr 2008
    Location
    Chicago (USA)
    Posts
    73

    Default

    Quote Originally Posted by XCovlov70 View Post
    I wondered after reading about your 'jolt' if it might be attributed to a 'problem' with the Electronic Parking Brake not backing off completely even though you have not used it.

    I was told that my rear pads wore out rather quickly due to the fact that when I pressed the brake pedal it 'charged' the rear brakes and put the pads up against the discs/rotors, so if they don't immediately back off as you accelerate again and are waiting for the 'sensor' to kick in then might this be the cause of your 'jolt'?
    Just a thought......
    Interesting. So this could be a brake system issue rather than a transmission issue. I'm in the dark as to how "pre-charging" the brakes is supposed to work.

  4. #4
    Join Date
    Nov 2009
    Location
    South Wales UK
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    1,901

    Default

    Quote Originally Posted by RichS View Post
    Interesting. So this could be a brake system issue rather than a transmission issue. I'm in the dark as to how "pre-charging" the brakes is supposed to work.
    It might be worth looking into as a brake system issue, while like you I am also in the dark about 'pre-charging'. I am only passing on the information given to me by the Volvo Dealer's Service Manager who also does interestingly get his hands dirty unlike some I've met.

  5. #5
    Join Date
    Nov 2011
    Location
    SEMA
    Posts
    31

    Default

    Make certain that your dealer has flushed the adaptive transmission memory, so that the car can have a fresh chance to accommodate itself to your particular driving style. I would suspect that the car had adapted its tip-in to the previous owner and you drive very differently. And ask the dealer to check both the ECM and TCM software to make certain that they are both current. I have the same XC70 as you, bought in January of 2012, and it didn't really shift and accelerate well until August of 2013, when the TCM software was upgraded for the second or third time. For the past 14 months, it has performed perfectly.
    Current Volvos:
    2015.5 V60 T5 Drive-E FWD Seashell/Beige, Platinum, Front Heat, BLIS, Urbane Wood, 18" Titania Rims
    2015.5 V60 T5 Drive-E FWD Power Blue/Off-Black, Platinum, Front Heat, BLIS

    Former Volvos:
    2012 XC70 T6 AWD Twilight Bronze/Espresso-Sandstone; 2012 S60 T5 FWD Saville Grey/Off-Black; 2010 V70 3.2 Seashell/Sandstone; 2008 S40 T5 Orinoco Blue/Quartz; 2007 V50 T5 Barents Blue/Quartz

  6. #6
    Join Date
    Sep 2014
    Location
    Sonoma County CA
    Posts
    7

    Default

    So it's not me, my 2014 does the exact same thing under those conditions, like it has not finished the downshift to first. Exactly the same scenario, slow then go and it slips then locks up and goes. Only on slow rolling conditions.
    I thought it was my hand controls I use causing it but they are very smooth otherwise and no issues in the other vehicle I have. I think I'll see if the dealer will clear the memory and go with that. My car was going to be a dealer vehicle but it never got registered and had 300 miles on it at delivery.

    Mark

  7. #7
    Join Date
    Apr 2008
    Location
    Chicago (USA)
    Posts
    73

    Default

    Quote Originally Posted by stsmark View Post
    So it's not me, my 2014 does the exact same thing under those conditions
    Service advisor says it's "normal" for the car

    Quote Originally Posted by stsmark View Post
    ... like it has not finished the downshift to first.
    Yes, at least that's how it feels to me: as if the transmission starts out in 2nd gear, then shifts to 1st. That's what I thought was happening. However, unlike an actual gear shift, if I listen to the engine/stare at the tach, there is no change in engine speed that I can detect during this period.

    I'm assuming you have the T6 ... correct?

  8. #8
    Join Date
    Sep 2014
    Location
    Sonoma County CA
    Posts
    7

    Default

    Exactly the same, engine does not race just a lag and a lurch. No clunk or noise. Everything else is perfect and it's not every time. About the time I think it's done doing it Murphy's law kicks in and it happens. Yes I have a T6.

  9. #9
    Join Date
    Nov 2002
    Location
    SE WI
    Posts
    1,308

    Default

    My belief is that it is due to the electronic throttle system parameters.
    The 'gain' is simply set too high and from a stop or near stop a slight accelerator movement results in an excessive engine input.
    Not anything to be done, my wife drives the 2011 and thinks it's fine, I rarely drive it and think it stinks.-Dick
    '11 XC70 Silver/Off Black-Hers
    '03 XC70 Silver/Charcoal-His
    '99 XC70 Silver/Charcoal -Granddaughter's
    '87 740GLE Junk Yard@287K miles
    2013 Porsche Boxster
    2017 Porsche C4S

  10. #10
    Join Date
    Apr 2008
    Location
    Chicago (USA)
    Posts
    73

    Default

    UPDATE: The car now has just over 49,000 miles on the odometer. As the end of the original mfr. warranty is near, I decided to revisit the issue by bringing the car to another area dealer for evaluation. The service tech was able to observe the behavior I described but affirmed the car was 'operating normally for this model'. No fault codes were detected and the TCM software is current. What was disturbing, though, was that the tech noted that the trans fluid was "VERY DARK AND BURNT". When I asked the obvious question (why not change the fluid/flush the trans?) the service advisor recommended AGAINST this. What??

    Here's what he said: 1) I would have to pay for this myself (I suppose I could live with that) and 2) changing the transmission fluid could adversely affect the transmission. If that were the case, any repairs or service might not be covered by the warranty (CPO until 2019). I left wondering why anyone on earth would suggest driving a car with transmission lubricant in this condition. Is there no way to effectively remove and replace the contaminated transmission fluid for this trans?

    Needless to say, I initiated a complaint with Volvo Customer Care and am waiting to hear back from them.

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