hard jerk under throttle in low rpm in 1st, 2nd gear
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This is a discussion on hard jerk under throttle in low rpm in 1st, 2nd gear within the General Maintenance, Troubleshooting & Accidents. forums, part of the Tech & Modifying & General Repairs category; Hello, I just got my 2005 Saab 92x Aero (2.0L Turbo WRX Wagon). I just got the car from the ...

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    hard jerk under throttle in low rpm in 1st, 2nd gear

    Hello,

    I just got my 2005 Saab 92x Aero (2.0L Turbo WRX Wagon). I just got the car from the dealer and its got around 80,000kms on the odometer. I have been noticing that sometimes when im in the low rpms around 1700 - 2000 rpms and im in 1st or 2nd gear when I lightly press the throttle to accelerate there is a hard jerk in acceleration and then it smooths out, sometimes its smooth as it should be. Does anyone know what this can be caused by? anyone have similar problems?

    Thanks!

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    Registered User Sarra's Avatar
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    Is the throttle itself sticking? Sounds like it could use a cleaning. If that's not it, it could be a variety of things. Do you ahve a boost gauge? Is the car tuned? Mods? etc.

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    hmmm i dont think the throttle is sticking, also i have no mods its completely stock with no boost gauge.

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    Registered User GageP's Avatar
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    Is there a Check engine light on?
    When you do things right people wont be sure you've done anything at all.

    Crabcakes and football thats what Maryland does.

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    nope no check engine light,

    also i should mention the hard jerks dont happen when i shift, its only when the car is already in gear 1 or 2 (clutch not depressed). when i let off the throttle and/or coasting and the revs are low and i get back on the throttle that the car jerks and then its fine. could it be bad detonation?

    im not sure if the revs jump when this happens or how much, i'll have to watch my rpms tomorrow if it happens again.

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    Registered User GageP's Avatar
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    i had the same problem when i would start in 1st and shift in 2nd, i had a cyl. misfire. i had all the injectors cleaned out and new spark plugs and coil packs put in and that sloved the problem. i would check the spark plugs and coil packs and see if one is bad.
    When you do things right people wont be sure you've done anything at all.

    Crabcakes and football thats what Maryland does.

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    wow cylinder misfire, that doesnt sound good, wouldnt that trigger a check engine light?

    i wonder why it only does it at low rpms tho. I will have to have the dealer take a look at it

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    or could this be caused by 87 octane gas in the gas tank?

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    Moderator YBNormal07's Avatar
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    Sounds like drivetrain backlash to me. It might depend on your point of reference...what cars you are used to, etc.

    The WRX (AeroX) is not the most "smooth" drivetrain you will ever drive, and it will transmit backlash, especially when getting on and off the throttle in the lower gears.

    To be safe, see if you can rotate the rear driveshaft with the engine off and in gear. Push it up and down, front to rear, and also try to rotate it. Listen for clunking noises. It's very rare (in fact I've never heard of it), but severe backlash can be a result of the a loose u-joint connection, which is something you do not want to have happen.

    I predict it is just normal backlash, and you may have to just get used to it. See about a ride with a similar year WRX and see if it does the same thing.
    tEh PriUs=teH faSTah!@@!
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    now that you mention it, it does feel like drivetrain lash. I felt that to a lesser degree in my previous car which was a mazda6 v6. I guess its just more apparent in the wrx.

    im guessing to get rid of this i would need to buy some engine mounts? as thats what i had to do with my mazda3 and mazda6

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    Moderator YBNormal07's Avatar
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    New bushings for the trans mount, pitch mount and new engine mounts will cushion it for sure. I just live with it and adjust my driving habits accordingly.

    Really, these drivetrains had some decent "slop" in them, so how it feels is more of a driver preference than anything else.
    tEh PriUs=teH faSTah!@@!
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    Registered User wrx0131's Avatar
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    This sounds normal to me. When I step on my gas hard from first gear, my car bucks a little too. You just have to ease and control how hard you step on the pedal.
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    ya i just drove to lunch, this definately feels like driveline lash. but this happens even when i lightly push the throttle when im in low revs below 2200 rpm. im hoping my motor mounts arent messed up.

    i think i will start with that transmission & pitch mount from Kartboy.

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    Registered User Sarra's Avatar
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    My WRX is my 5th Subaru. Weirdly enough, all of my Subies have had 80K or more (miles, not KMS) on them, including my WRX. So far, my WRX has been the smoothest at low RPM's, especially in first gear. 2 mph, first gear, left foot on the dead pedal, play with the gas a little and it is smooth. My previous cars were another story, especially the 1985 GL Turbo, but that car had 290+K on it. If it's jerky, then I would suspect something is worn out or needs to be tightened, go to someone who knows suspensions well and ask their opinion.

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    Moderator YBNormal07's Avatar
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    Quote Originally Posted by poopeebum View Post
    ya i just drove to lunch, this definately feels like driveline lash. but this happens even when i lightly push the throttle when im in low revs below 2200 rpm. im hoping my motor mounts arent messed up.

    i think i will start with that transmission & pitch mount from Kartboy.
    Does it buck just once when you lightly applly the throttle, or does it keep doing it as you increase throttle?
    tEh PriUs=teH faSTah!@@!
    08 Audi S5 Black Diamond edition
    SOLD: 05 SWP Legacy GT Limited 5MT, 13.3ish@105 (stage 2) crappy stock clutch
    SOLD: 04 MPS/SW WRX Sti. 12.971 @ 103.97 (stock)
    278 AWHP/283 AWT, Catback exhaust
    306 AWHP/341 AWT, Stage 2
    (Scott) Moderator-STi, Drag Racing, Car Purchasing, and Tutorial Forums

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