Car jerks sometimes when going over uneven surfaces...

[singleframe]

Been driving my RS4 for a few months now and noticing when in lower speeds, usually while shifting gears, as I go over uneven surfaces...bumps/dips in the road, etc. the car will jerk quite abruptly and keep doing so until I pull off the gas. Anyone else ever have this issue??

[two2]

well if your foot isn't jerking the petal and you're rev matching on shifts then it could be mounts, tranny, motor, torque,etc..

[Alister]

Is this only with having Sport mode on, or all the time?

Any idea if your car has had a service campaign carried out that saw the software versions on the engine ECUs updated?

[singleframe]

been trying to reach the dealership's service dept today to check on the ECU.
happens in both sport mode and normal mode.

::update::
they say I need to bring it in and hook it up to see if it has the latest software. ugh.

[Mistro]

And you're sure it's not just your feet + ESP kicking in?

[singleframe]

And you're sure it's not just your feet + ESP kicking in?

btw, it's more often after cold starts... I'm going to turn ESP off and see if this changes things.

[RS4in206]

Hopefully its just an issue of getting use to the throttle. Many of us had that issue when we first got into the car. That and getting use to the 1st to 2nd shift points.

[singleframe]

yeah that's part of it for sure...I was also driving my A3 a few days a week until I just sold it. Night and day!!!!

[Datadatum]

Cold engine + uneven surface + hovering foot over gas pedal = herky jerky acceleration

When the car jerks, your foot jerks, and you experience something like wave amplification. It will be worse with S mode, as it increases throttle sensitivity AND reduces response time.

[BigMacAttack57]

Hi !! I'm new here. I can't solve your problem, but I can share my similar experience. I'd be willing to bet that your experience is NOT being caused (directly) by your foot.

I have been experiencing this same behavior (and worse) over the course of the past couple of months, though I've been driving my RS4 for over a year. Looking back, I think that my RS4 has been doing this (and other things like it) for a while. I just thought that it was me and the way I was driving the car and the RS4 being a little "goosey", what with all the horsepower and such. It seems to have gotten worse recently. The bottom line is that I think that this is an ECU program / firmware / mapping issue. Here's why I think that.

I have noticed the behavior that you have described when pulling away from being stopped at a traffic signal, while accelerating and under moderate load at somewhat-lower RPM and crossing railroad tracks just on the other side of the intersection. This may be the ESP kicking in, if the wheels break traction as we drive over the tracks (with a little bounce as we cross them).

I experience a much more pronounced version of this in another situation that is much more common. I have noticed this behavior when pulling away from being stopped at any traffic signal. Obviously, I accelerate from stop in first gear. If I wind out the engine to about 3K RPM in first gear, such that I engage second gear at about 2K RPM, and then press the accelerator pedal to a medium-aggressive level, the car accelerates - BUT the acceleration includes a strange, "sinusoidal variation in RPM increase rate". The RPM will ramp from 2K RPM to, say, 5K RPM, but not linearly. The car exhibits a strange "thrust then retard" characteristic up the RPM ramp, at approximately a 1 Hz frequency, and it is very pronounced, particularly in the 3K - 4K RPM range. This strange variation definitely seems to me to be under ECU control. It is not random misfiring. It is not "carbon buildup". It is too smooth for either of those.

I can't say whether it is related to an issue with the mappings in the ECU and a possible recent seasonal change in the amount of ethanol in the gasoline around here. I only run "top tier" gas - Chevron Premium. The "fall-to-winter" transition has just occurred here in Texas and ambient temperatures vary wildly with seasonal changes. I can't say whether it is related to the ESP "cyber nanny" (or some other ECU-internal software control loop "cyber nanny") kicking in too aggressively. I have tried the trick of turning off the ESP [solid light] and it "seemed to help some". I can't say whether it is in some way related to the "driver adaptation / learning process" that I have read that the ECU undertakes to learn the driver's driving habits and operational patterns. I will say that it strikes me (from a sensory perspective) as an "oscillatory control loop" issue, one where some ECU control loop (including "software in the loop" within the ECU) seems to be operating in a borderline-stability fashion with this particular combination of conditions (RPM / shift point, accelerator depression / engine load, fuel, ambient temperature, ...), resulting in this sinusoidal, oscillatory behavior.

If I wind the engine out further in first gear (to, say, 4.5K RPM), such that I engage second gear at around 3K RPM, the car does not exhibit this behavior. Yes, one could say that I should just always do this and avoid the problem. Real driving - in the city, in traffic, in the real world - doesn't afford one the opportunity to "always wind it out in first gear", of course. A car that is driven in the real world must be capable of operating smoothly in all combinations of "normal conditions".

I recognize that I am taking somewhat of a "shot in the dark" here.

I hooked up my VAG-COM pod / VCDS today for the first time in a long time and dumped the ECU firmware info. It appears that I'm only at version 0060 of the ECU firmware (both ECUs). I would like to clear the "driver adaptations" back to the basic default setting and see whether doing so changes this behavior. I am sure that I will soon be at the Audi dealer getting the ECU firmware updated to version 0090, which I have read is the latest version.

Can anyone give me tips on either of the following ?? How does one use the VAG-COM pod / VCDS to clear the ECU "driver adaptations" back to the basic default setting ?? Can one / how does one use the VAG-COM pod / VCDS to update the ECU firmware themselves and where can one get the version 0090 firmware ??

I'll refresh my post as / if I learn anything more. BMA57

[1SICRS4]

bump steer

[NY07RS4]

It's your foot bouncing on and off the gas pedal. Rest the side of your foot against the foot well wall when going over bump to steady it at slow speeds. Happened maybe twice when I first got the car, realized it and adjusted. Hasn't happened since. I highly doubt anything else is contributing to throttle input just by driving over bumps. It's your foot.

[tadhgbrosnan]

Same exact thing occurs in my car. I attribute it to a hyper-sensitive throttle. There is one stop sign/intersection in my town where it happens virtually every time I drive thru. Bumpy, uneven road surface & if I am not very careful to keep my foot perfectly still, the movement can cause the jerking throttle reaction that the OP experiences.

Had similar experiences in my B6 S4, too. Never in my B5 S4, though.

[BigMacAttack57]

I'm not really concerned with the occasions when I experience this behavior over bumpy roads or railroad tracks - those occurrences are pretty rare for me.

Most of my post was related to "straight ahead" launch from a traffic signal on any flat suburban (divided 3 + 3 lane) road - no dips, no bumps, straight ahead. My experience is not related to my foot bouncing off the gas pedal. I'm experiencing a variation of +/- 250 RPM as the car accelerates up a ramp from 2K RPM to 5K RPM. The car goes through as many as three "surge / retard" cycles in going from 2K RPM to 5K RPM and is associated very closely with accelerator pedal depression depth and engine load.

This behavior occurs if I let the engine drop to 2K RPM in shifting from first gear to second gear and then press the accelerator heavily. I do not experience it all if I only let the engine drop to 3K RPM in shifting from first gear to second gear and then press the accelerator heavily, everything else being equal / exactly the same. The extra engine load in the 2K RPM shift scenario seems to be near "ground zero", as far as what it takes to excite the behavior.

Thanks for listening, BMA57

[singleframe]

I'm curious what version I'm running. I'll have to check it out after the holidays...

[BigMacAttack57]

tad: In your situation, I recommend trying an experiment at that intersection.

Push the ESP button and hold it for five or six seconds, such that the ESP is as "off" is it can be (the "car swerving on the road" indicator in the instrument cluster should be on solid, not off or flashing).

Try your launch at / through that intersection with the bumpy surface again.

Now the ESP is not monitoring for "tire breakaway", which may be occurring slightly as you cross the bumpy road (or that's how the ESP may be interpreting what it's sensing anyway). I've tried something similar when crossing railroad tracks and the jerking seemed to go away with the ESP off.

Turning off the ESP didn't correct the other "launching on a smooth road" jerky behavior that I described in my previous post.

BMA57

[singleframe]

It appears that I'm only at version 0060 of the ECU firmware (both ECUs). I would like to clear the "driver adaptations" back to the basic default setting and see whether doing so changes this behavior. I am sure that I will soon be at the Audi dealer getting the ECU firmware updated to version 0090, which I have read is the latest version.

What does version 0090 do better than 0060? Is this a necessary upgrade??

[BenSti]

What does version 0090 do better than 0060? Is this a necessary upgrade??

My understanding is that it makes the drivability a little better when cold. But makes no changes when hot.

[baggednbangin]

you foot is bouncing when going over bumps. i experience the same thing. sometimes i do it during daily driving. all you need is a little jerk and then every time your foot lets off and get back on the gas it will cause a more and more violent jerk from the car.

it is not esp kicking in otherwise you would see the light start flashing and it would cut the power not introduce more!

i experience it even more now and even more violently with a light weight flywheel.

its just the nature of the beast. try not to feather the throttle while going over uneven surfaces. or you can just let off the gas and start again.

the problem isnt the car, its the driver.