Intermittent bucking jerking while driving

Hi Guys,
I've been searching for weeks and tried a few things to sort this issue out but not really getting anywhere.
I recently purchased a 2011 A3 2.0tdi 170 CBBB Black Edition. I test drove it on two separate occasions and all was fine, car had good and honest history.
A few weeks later I noticed it buck while on the motorway, was so slight and minute and having experienced this with bad fuel and a bad filter on my cupra tdi i decided to change the filter out. At the same time I also circulated some liqui moly through the injectors, but the problem was still there.

Basically the car will buck (almost like it is spluttering) at random speeds/RPMs.
I disconnected the air control valve on the manifold and the problem disappeared so I thought that might be the culprit, I replaced it with an original and cleaned out as much out the manifold as I could.
The problem seemed to have gone for a day but returned and was no different than before. One time the car spluttered and stalled after starting it before a long journey, the only way to get around it was if I disconnected the air control valve (butterfly valve/anti shudder valve VDO 03l128063k).

Can someone please help me out? I'm sure there is an answer/fix for this, the people with similar problems on all the old posts I've read haven't reported back on whether they managed to solve the issue.

Thanks

Boost leak. Do you hear a hissing sound wen the bucking happens?

Its definitely not a boost leak, I disconnected the outlet from turbo, capped other end at intake and used my mityvac to test it and it was good.
No black smoke and no fault codes come up (apart from when I take the connector off the valve).
Apart from the occasional bucking (as if it is intermittent fuel starvation) the car runs smooth with plenty of power.
No odd sounds or anything like that.

I know nothing about the A3, however, it sounds like a bad lift pump if you have one or could even be a clogged vent causing a vacuum in the tank.

The intermittent aspect makes it tough to diagnose.
I recommend looking into removing the valve in the tank and seeing if that solves it.

As far as the lift pump idea, is there one on that car? If so, check for proper operation.
It could be on its way out and overheating loosing function.

eddieleephd said:

I know nothing about the A3, however, it sounds like a bad lift pump if you have one or could even be a clogged vent causing a vacuum in the tank.

The intermittent aspect makes it tough to diagnose.
I recommend looking into removing the valve in the tank and seeing if that solves it.

As far as the lift pump idea, is there one on that car? If so, check for proper operation.
It could be on its way out and overheating loosing function.

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Thanks Eddie, I don't think it is the lift pump...if it was then it doesn't explain why the problem goes away after unplugging the air control valve.

Anyone else?
Today I started the car and on idle it was really jerky and suddenly cut out, did it a cuple of times and the only way to get around that or actually drive the car was to disconnect the air control valve.
Can anyone shed some light on what this could be?
Thanks

On any of our BEW and BRM north american cars the anti-shutter valve is used to help control EGR operation. The nylon gear operation of the butterfly valve can go bad and strip the gear teeth. Remove and inspect. if it looks oK I would suspect an air leak some where in your fuel line causing air bubbles as a more likely culprit.

A Mitey Vac will tell you zip about a boost leak. The bucking thing while accelerating is a dead giveaway for a boost leak.

Hold the brake and feather the clutch while standing still. You will come up on boost and any boost leak will become apparent with a hissing sound.

We had a very vexing issue on a 2010 CBEA that just might be what you are experiencing. The fuel lines for the early models would get a pressure 'bounce' in the line and it would cause, in our case, the #2 injector to sputter, to the point it would stop working. If you stopped, and restarted, the car would once again, operate normally for a while, and then repeat. We spent too much time diagnosing the issue, and finally gave up and thought, "It must be the ECU". $1100 later, it wasn't the ECU and we really got fried by the local dealership. The end of that story is a whole 'nother story...

In the end, we found out that many VW's were experiencing the same stutter and shudder. The cure VW created was to install some small rubber bushings around the fuel lines...'dampeners' as best I could describe them.

Check to see you have that rubber bushing on each of your fuel lines going from the common rail to the injectors.

Franko6 said:

We had a very vexing issue on a 2010 CBEA that just might be what you are experiencing. The fuel lines for the early models would get a pressure 'bounce' in the line and it would cause, in our case, the #2 injector to sputter, to the point it would stop working. If you stopped, and restarted, the car would once again, operate normally for a while, and then repeat. We spent too much time diagnosing the issue, and finally gave up and thought, "It must be the ECU". $1100 later, it wasn't the ECU and we really got fried by the local dealership. The end of that story is a whole 'nother story...

In the end, we found out that many VW's were experiencing the same stutter and shudder. The cure VW created was to install some small rubber bushings around the fuel lines...'dampeners' as best I could describe them.

Check to see you have that rubber bushing on each of your fuel lines going from the common rail to the injectors.

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Frank thanks for the interesting insight.
What is really bugging me is that the issue will completely dissapear when i disconnect the air control valve. I've had it disconnected for a week now and the car drives faultlessly, allbeit with the CEL light on and glow light flashing.
This goes away if I re connect the air control valve though...

I wonder if the problem lies with the actual egr that sits up the back of the engine?

Hi Guys, I still have this issue! It was sort of resolved after I was at a loss and asked Darkside to have a look at it who assured me it was the air control valve.
It was replaced with a new genuine part and the problem did dissappear, but not for very long.
After a few months the bucking returned. No issues with staring now (before I did have issues where it would just crank and not start until the valve was disconnected - battery changed so this problem seemed to have been down to a poor battery....not sure how/why?).

Can someone point me in the right direction as to what I can start looking at or logging?

Thanks

uzi_cupra said:

After a few months the bucking returned.

Can someone point me in the right direction as to what I can start looking at or logging?

Thanks

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Please quantify the amounts involved. On my '03, it's at most 100 rpm when around 1900 rpm, around 50 rpm near to each side, and is unnoticeable elsewhere. It occurs about once a minute. Also, after you removed the air control valve, did the engine run longer than usual after turning the key off? Were there any other drawbacks? I'm thinking of removing mine to avoid the problem. Did it occur when on cruise control at around 88km/h?

Not sure if anyone is still reading this thread - I had a similar issue with my 2015 Jetta TDi (200000km, very well maintained) The car would intermittently jerk/buck - would happen at highway speeds as well as around town. Happened across all gears. Would temporarily lose power, rpms would drop and then quickly recover. No MIL or other warnings would appear. My fuel economy also started to drop over time. Technicians at VW worked with VW Canada to diagnose and address issue (which was hard because there were no error codes generated). Checked turbo boost sensor, fuel filters, MAF - made no difference. Eventually replaced the camshaft sensor. problem solved. Car runs like new. No further issues. Hope this helps

Great info! OP has not been active for over a year.

orilius said:

Not sure if anyone is still reading this thread - I had a similar issue with my 2015 Jetta TDi (200000km, very well maintained) The car would intermittently jerk/buck - would happen at highway speeds as well as around town. Happened across all gears. Would temporarily lose power, rpms would drop and then quickly recover. No MIL or other warnings would appear. My fuel economy also started to drop over time. Technicians at VW worked with VW Canada to diagnose and address issue (which was hard because there were no error codes generated). Checked turbo boost sensor, fuel filters, MAF - made no difference. Eventually replaced the camshaft sensor. problem solved. Car runs like new. No further issues. Hope this helps

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I have the identical issue with my 2015 Jetta. I have been searching and cannot for the life of me find a cam position sensor for my car do you by chance have anymore info on what exactly they changed?

Dannyboy said:

It's under the fuel rail on the head between cylinder 2 and 3 glow plugs on ea288 engines.

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I ended up locating it. Thank you very much though Danny! I appreciate it.

I just wanted to follow up and say that I had identical symptoms and that replacing the cam position sensor solved my issue as well, no more bucking.

I have the exact issue now after changing the egr valve it failed and when it did it threw the cam shaft sensor but I cleared all the codes and the mechanic couldn’t find that again but it’s still doing this after changing fuel filter and running liqui moly thru it and carbon clean but I reckon it’s this and a dirty injectors being, I’m looking at doing an egr delete but not completely as I don’t want to re code it all, Thanks for this thread it helped the diagnosis for the mechanic as it was the cam shaft position sensor and dirty injectors.

I am experiencing the same symptoms with my 2015 Jetta SEL 6 speed manual- 72,800 miles. Its having an intermittent engine shudder in all gears, with no codes. I first noticed it in 5th gear while gently accelerating around 55 MPH. It then began occurring randomly in all other gears/speeds as well, most noticeably when pressing the accelerator; I sometimes feel a quick RPM drop off while sitting in neutral too, but its gentle as I'm obviously not moving. The best way to describe what it feels like would be if you pressed the clutch for a split second and felt the car buck. RPM seems to drop when this occurs. Note: This is not occurring while shifting, but rather while the car is already in gear. I had to leave the car with the dealer and have the technician drive it a few days as you never know when it will occur. It seems the most likely conditions for it to occur are on the second drive of the day, after the car sits for an hour or more. Technician is thinking pressure plate or flywheel, but I am not convinced the symptoms match. VW of America is suggesting a transmission teardown, which my extended warranty would not cover unless an internal part is to blame. I am not mechanically savvy, so please respond accordingly

TimmyCee said:

I am experiencing the same symptoms with my 2015 Jetta SEL 6 speed manual- 72,800 miles. Its having an intermittent engine shudder in all gears, with no codes. I first noticed it in 5th gear while gently accelerating around 55 MPH. It then began occurring randomly in all other gears/speeds as well, most noticeably when pressing the accelerator; I sometimes feel a quick RPM drop off while sitting in neutral too, but its gentle as I'm obviously not moving. The best way to describe what it feels like would be if you pressed the clutch for a split second and felt the car buck. RPM seems to drop when this occurs. Note: This is not occurring while shifting, but rather while the car is already in gear. I had to leave the car with the dealer and have the technician drive it a few days as you never know when it will occur. It seems the most likely conditions for it to occur are on the second drive of the day, after the car sits for an hour or more. Technician is thinking pressure plate or flywheel, but I am not convinced the symptoms match. VW of America is suggesting a transmission teardown, which my extended warranty would not cover unless an internal part is to blame. I am not mechanically savvy, so please respond accordingly

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Happening to me now (Saturday), though it has happened earlier this year and last year. Recently though I backed up a steep winding hill (last Wednesday) and the clutch smell was terrible afterward. No codes (except for steering angle), but the chugging cleared up after we let it sit for a few hours. Engine light is on, now, however.

Edit: Changed the can shaft position sensor (broke the tab on the sensor lock, lol that is a tiny tab, and stripped the torx bolt on the second fuel line stabilizer that actually does not have to be removed to get access to the CSPS as long as you remove the first bolt on that line) over the weekend and I have not experienced the effect since then (3 days), and I don't know if its placebo effect, but it seems like the car is running more smoothly even without the shuddering occurring. I didn't realize the CSPS was making the general operation not run smoothly. so +1 for CSPS causing this.