Engine lumpy idle/tickover

[dirk1978]

Resurrecting another old thread. My 06 VRS TFSI does this.

The tickover is perfectly smooth from the rev counter and the engine note, but it wobbles. The car like trembles sometimes. Perhaps slightly worse when cold but sometimes does it and sometimes doesn't.

I'd like to think it's not the DMF, but it doesn't have any of the common symptoms anyway.

It may well be the obvious coilpack issue but I've been told it went in for a recall to have them swapped out.

Is this very common? Any suggestions other than the above?

[rossm]

It could be the Throttle Body Alignment needing done - this would cause it to run less-smooth and might not generate any faults or engine / emissions lights. If you've got VCDS, it's a 2 min job, if not, it may be worth finding someone who has to get it done.

Particularly likely if the battery has ever been disconnected, details here:

http://wiki.ross-tech.com/wiki/index.php/Throttle_Body_Alignment_(TBA)

If it was a regular occurring misfire, you'd get the emissions light on the dash.

[dirk1978]

Good shout. I've got vag com, got a cable but no windows laptop to run it. It used to work in Linux fine using wine but the ftdi usb-serial drivers keep disconnecting now. I'll give it another go. Cheers.

Sent from my Galaxy Nexus using Tapatalk 2

[SKODA OCTAVIA]

same for me has rolld 13 000 km

[Stu08]

I have the same slight miss on idle occasionally. Appears to be a trait of this car. Passed the emissions test on its MOT last week with flying colours.

Car doesn't miss once above idle. Pulls hard to the redline.

[westy-vrs]

I have the same problem but the car is fine other than that . I just live with it lol

[Marc Davison]

My 57 plate tfsi vrs does this after start up at idle and initial start is lumpy. Drives fine once going no hesitation or anything like that. It's got 74k on it and my assumption is that it's the vag tfsi carbon build up / coking but not sure how widespread this actually is...

[Stu08]

Not very wide spread at all mate. A couple of examples have occured in UK. It however; appears to be a larger problem across the pond.

This has been linked to poorer quality fuels and oils.

It also seems to be more of a problem on the NA 4.2 V8 found in the RS4. Whether there is a link to NA over turbo I'm not sure. Have read arguments stating turbo charged direct injection engines combust at a much higher temp due to the boost.

Again- I do not know the ins and outs, but seems plausible?

[R8MXX]

Carbon Build Up is still a UK issue. Its not to do with Oil/Fuel quality in America as the Fuel does not touch the tops of the intake valves on the FSI direct injection engines due to the way the fuelling is setup. If it did we would not have the coking up issue as the injected fuel would keep the intake valves clean. I have a friend who is a Master Tech at a Seat dealer and says he has needed to do a manual clean of the intake valves on several occasions on higher mileage FSI's and TFSI's due to the exact issues being mentioned here.

I have been fighting this problem for the last 10 months of ownership and also the last owner of the car said he had the issue but has worsened since I have owned the car. I have the 2.0T FSI BWA engine but it is also occuring on the 2.0 TSI's from what I have been reading on the forums.

So far I have changed coil packs, cleaned and reset throttle body, changed manifold intake flap runner motor and next stop is the cleaning on the intake valves due to my car being on 100k and seeing a photo like this yesterday from a TFSI engine on 100k - resembles a coral reef!

I will post photos of the state of my intake valves on Monday evening once I have completed the job and report on how it now runs

[chr1staylor]

I'd recommend anyone who has the issue in the original post to change their PCV valve as a matter of course, especially if you have an earlier TFSI. The pcv is a known weak point/failure causing lumpy idle and (assuming you can get the engine cover off) is a piece of cake to replace, and the part cost is only around £30 from a dealer.

[R8MXX]

I'd recommend anyone who has the issue in the original post to change their PCV valve as a matter of course, especially if you have an earlier TFSI. The pcv is a known weak point/failure causing lumpy idle and (assuming you can get the engine cover off) is a piece of cake to replace, and the part cost is only around £30 from a dealer.

Forgot to say, I have also replaced the PCV valve on mine! Should have been in the list above...

[Remusrrr]

I have same thing on my 57 plate change pcv still the same

[whitep]

what happens if you put the rear demister on...?

[Remusrrr]

Don't know never paid atention to that

[westy-vrs]

Nothing noticeable happens when I put my rear demister on tbf

[dirk1978]

I've got a can full of ethanol and I'm determined to use it!

I'll give the TB a good clean out this week and report back.

[dirk1978]

Throttle body (semi) clean didn't really do much. Or actually, it's not quite as violent as it was.

 

I've logged some data over OBD while it was happening and got some interesting results:

 

 

This was when I was sitting for a couple of minutes with it happening slightly, then pulling forward (increased values) and back to idle. Few things to note.

 

1. Top line is coolant, rises slightly by a degree or 2 around 81, 82 which is expected from sitting idling. CTS is fine.

2. Next is IAT around 31 degrees. Again rises slightly from idling heat. Expected. MAF is fine.

3. Orange line is plotted on the left hand axis and is RPM. This is slightly up and down consistent with the lumpiness.

4. AFR and throttle position are both rock solid. This means there's no dodgy signal from the pedal or o2 sensor.

5. MAF and lambda are both solid. Again, the MAF and o2 sensor would seem to be fine.

6. Boost is solid. Turbo, MAP and boost controller would appear OK.

7. Finally, the timing advance is up and down with the RPM.

 

From everything being fine but the timing, it would seem to be either a dodgy knock sensor or just VAG making the stock map too lean from the factory on idle.

 

Any thoughts?

 

[R8MXX]

I would have a look at my thread on carbon build up on the intake valves - my car runs so much better now I have cleaned them out!

 

http://www.briskoda.net/forums/topic/273037-vrs-20t-fsi-stuttering-at-idle-and-on-acceleration-up-to-2000-rpm/

[dirk1978]

Had a good little read following all the links around various forums. Thanks.

 

That's a job for another day then

 

Mine's done 81k and is only slightly suffering from this problem so it's not desperate yet.

[Marc Davison]

Has anyone had Carbon deposits cleaned out by a VAG/Skoda indie, what sort of cost are you looking at to get this done?

[R8MXX]

Has anyone had Carbon deposits cleaned out by a VAG/Skoda indie, what sort of cost are you looking at to get this done?

 

I had mine done. I had a VAG specialist indy help me with mine and its a £300 job all in. You will need a new inlet manifold gasket and a complete set of injector seals just in case they dislodge when you remove the inlet manifold.

 

The specialist had never done it before and with him getting to know me quite well offered to do the strip down and rebuild of the inlet manifold and fuel system and for me to do the manual cleaning (which saved a lot of £££ so I paid nowhere near £300!). Its about a 5-6hr job + parts.

[dirk1978]

How hard of a job was the cleaning bit? I'm a decent mechanic and have a few tools. Is it just something like a long screwdriver, rags, intake cleaner etc?

[R8MXX]

How hard of a job was the cleaning bit? I'm a decent mechanic and have a few tools. Is it just something like a long screwdriver, rags, intake cleaner etc?

 

Don't use cleaner as it will make a 'soup' like carbon solution which will make the job 10 times harder. Obviously it has to be done in 2 stages so you can get TDC using the bottom pulley on 2 valves at a time - so all the crap doesn't fall into the cylinders while cleaning and you blow it out with compressed air or stuck it out with a hoover.

 

I got the worst of it off (the big lumpy parts) using a small electrical style screwdriver. Then I used a cable tie so get round the back of the intake valve (with the ribbed part against the valve) to get the deposits off the rear of it. Blew all that crap out with compressed air.

Next I used this (http://www.ebay.co.uk/itm/Silverline-Rotary-De-Carb-Brush-Set-wheel-cup-decarb-decoke-de-coke-/181088869824?pt=UK_Home_Garden_PowerTools_SM&hash=item2a29bcddc0) - De-coke brushes on a drill attachment. Only used the pointed one and got that in there on the drill (quite gingerly) and it did the rest. Blew all that out with compressed air. Then sprayed a little brake cleaner in there just to make sure there was nothing nasty left behind and dried it off with compressed air.

 

Thats how I got to the stage of clean that you saw in my other thread which was good enough tbh and pretty much solved my hesitation issues. Took about 45 minutes per intake valve - would probably take less time if I was really focused on it.

[Marc Davison]

Thanks for the info. Will bear it in mind for when it gets worse! Right now it only seems to be an issue starting and when at cold idle.

 

Marc

[R8MXX]

Thanks for the info. Will bear it in mind for when it gets worse! Right now it only seems to be an issue starting and when at cold idle.

 

Marc

 

I still have a certain amount of that at cold idle but have never had any hesitation in the rev range since the de-coke. It has certainly helped the issue thou.

 

The Indy I use say the 2.0T FSI doesn't idle totally flat anyway... Mine is a smooth as anything at idle compared against my mates Clip Cup 172 2.0 N/A!

Edited 12 July, 2013 by R8MXX