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Thread: Jerk When Letting Off or Getting on Throttle

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    Default Jerk When Letting Off or Getting on Throttle

    Hi y'all! 2010 hatchback, 5 spd. Over the last 6 months or so my car has developed this noticeable jerk when I let off the throttle, no matter how gentle I am it's always there. Obviously it's worse in 1-3, but I can still feel it in 4. Also slight vibrations at a stop light, I thought it was the passenger mount but that was just replaced. Dealership tells me the rear mount is in good shape, haven't checked the transmission mount yet. Could it be a combo of mount + sticky throttle body?

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    Default Re: Jerk When Letting Off or Getting on Throttle

    I would check all the motor mounts first, then go with cleaning the MAF + Throttle body.

    Good Luck.

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    Default Re: Jerk When Letting Off or Getting on Throttle

    Quote Originally Posted by ManualMazda View Post
    Hi y'all! 2010 hatchback, 5 spd. Over the last 6 months or so my car has developed this noticeable jerk when I let off the throttle, no matter how gentle I am it's always there. Obviously it's worse in 1-3, but I can still feel it in 4. Also slight vibrations at a stop light, I thought it was the passenger mount but that was just replaced. Dealership tells me the rear mount is in good shape, haven't checked the transmission mount yet. Could it be a combo of mount + sticky throttle body?
    OP, were you able to get this resolved?


    2010 Sport 2.0L 5MT

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    Default Re: Jerk When Letting Off or Getting on Throttle

    Quote Originally Posted by sarujo View Post
    OP, were you able to get this resolved?
    Not yet! It has to be the rear or transmission motor mounts I just don't have tools to get it up and look at them. I've ruled out throttle body because in neutral the revs fall correctly but anytime I apply power it feels like some crazy slack is being taken up, same with getting off the throttle. Are you experiencing the same?

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    Default Re: Jerk When Letting Off or Getting on Throttle

    For sure it is a mount

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    Default Re: Jerk When Letting Off or Getting on Throttle

    Installing the e-focus mount and getting that seat recall done on Thursday, will keep you posted. If I forget drop me a message, hopefully we'll be back to smooth sailing.

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    Default Re: Jerk When Letting Off or Getting on Throttle

    Update: seat is now noiseless going around corners! And the e-focus mount is awesome! Way tighter feeling on shifts and getting off the throttle. The old rear mount was getting worn but it was still intact. There's a few more vibes in the floorboard now but hardly noticeable and supposedly new mounts break in and chill out a bit anyways. A highly recommended upgrade. Also the jerk is much less pronounced, I can now get off the throttle at 3-4k without a massive buck/jerk.

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    Default Re: Jerk When Letting Off or Getting on Throttle

    Quote Originally Posted by ManualMazda View Post
    Update: seat is now noiseless going around corners! And the e-focus mount is awesome! Way tighter feeling on shifts and getting off the throttle. The old rear mount was getting worn but it was still intact. There's a few more vibes in the floorboard now but hardly noticeable and supposedly new mounts break in and chill out a bit anyways. A highly recommended upgrade. Also the jerk is much less pronounced, I can now get off the throttle at 3-4k without a massive buck/jerk.
    Good to hear.

    Clean the TB + MAF and then do an ECU reset. I recently did this and the car drove much smoother, but after a few weeks of "re-learning" things seem to be returning to jerkiness on shifts and after lightly engaging the throttle after coasting.

    The e-focus mount will definitely loosen up. I found over time it crept back to near stock feel and eventually I removed it as I was tired of the extra noise emitted into the cabin over stock.

    TBH, the mounts in our cars stink (crappy Ford design!). I changed both passenger and trans mounts (few years ago) and I think the trans one is getting bad again after about 60k. Will get Jimmy to inspect mounts during next oil change.

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    Default Re: Jerk When Letting Off or Getting on Throttle

    I have gooped all of my mounts up with urethane, as well as have installed the Corksport dogbone insert years ago. I get the same jerkiness (I clean my TB and air filter all the time) and all I can point fingers at is excessive play in the passenger side CV joint socket (where the half-shaft slides into the intermediate shaft). My engine barely moves with throttle blips.

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    Default Re: Jerk When Letting Off or Getting on Throttle

    Quote Originally Posted by morganc View Post
    I have gooped all of my mounts up with urethane, as well as have installed the Corksport dogbone insert years ago. I get the same jerkiness (I clean my TB and air filter all the time) and all I can point fingers at is excessive play in the passenger side CV joint socket (where the half-shaft slides into the intermediate shaft). My engine barely moves with throttle blips.
    I have done the exact same mods and experience the same jerkiness. It confuses me. Insert on the rear mount, new trans mount, and filled/replaces the passenger mount.

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    Default Re: Jerk When Letting Off or Getting on Throttle

    Quote Originally Posted by morganc View Post
    I have gooped all of my mounts up with urethane, as well as have installed the Corksport dogbone insert years ago. I get the same jerkiness (I clean my TB and air filter all the time) and all I can point fingers at is excessive play in the passenger side CV joint socket (where the half-shaft slides into the intermediate shaft). My engine barely moves with throttle blips.
    I started by cleaning the MAF and replacing the air filter and the car drove a bit better and mileage increased. After a week or two I decided to clean the TB and then reset the ECU (pulled the - battery). The car drove sooo much better right away and the "jerking" disappeared. It was perfect for about 5 days and then it slowly started to come back. After a few weeks I feel like it's back to like before. During this time I did nothing to my mounts.

    The dramatic improvement after the cleaning and ECU reset (followed by the return after the re-learn) leads me to believe it is some kind of sensor issue which causes minor motor jerking during off shifts and when gong back on the pedal post coasting. Sometimes I can actually see the tach bounce up and down a bit when the jerks happen.

    Perhaps we need to update the ECU? Or maybe these are quirks with the throttle body? I recall reading that some gen 1's had TB issues when dirty. Maybe there is something with the MAF sensor? I used a K&N drop in for years but have now switched back to a regular quality air filter.

    What type of air filters are you guys using and what mileage do you have?

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    Default Re: Jerk When Letting Off or Getting on Throttle

    Well with the manual trans it clearly jerks between the transition between fuel fed and fuel cut off to engine braking. Because the mount are just rubber pieces I can't see any interference from sensors. There is some mechanical movement that is causing the engine to shift large amounts.

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    Default Re: Jerk When Letting Off or Getting on Throttle

    Update 2: the jerk is still there if I let off around 2k, due to the throttle body it seems like. 3k and up is smoother. Definitely feeling some vibrations but I'm hoping they diminish a bit in time.

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    Default Re: Jerk When Letting Off or Getting on Throttle

    Quote Originally Posted by jeff7670 View Post
    Well with the manual trans it clearly jerks between the transition between fuel fed and fuel cut off to engine braking. Because the mount are just rubber pieces I can't see any interference from sensors. There is some mechanical movement that is causing the engine to shift large amounts.
    Still doesn't fully explain why the jerking went away after a TB clean and ECU reset...only to return days later after re-learn...if it was mechanical and/or mounts then ECU reset + clean would have done nothing. Has to be something with TB/sensor(s)/ECU.

    Doing an oil change in October and a bottle of Redline SI-1 is part of my/this maintenance regime. Will pay close attention to see if this provides any improvement.

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