Slight lumpy idle when cold.

[BASSCUBE]

My car drives sweet as a nut most of the time.

Occasionally the car doesn't start first time but will start the 2nd. Then it runs really rough like you can see the needle swaying slightly.

I hear this is a common fault on the 2.0 tdi engines.

Any ideas?

Some people think can be DMF but i doubt it. More likely to be a choked up injector or egr valve?

[BASSCUBE]

Hello???

[TriGGER]

Get it into a garage mate.

[Roy_01]

Sounds like an injector problem.

[lewisheywood]

TDI you're likely looking at either glow plugs (most probable) or injector . Rough idle usually occurs when fuel isn't being burnt properly hence the engine doesn't run as it should and the rpms aren't stable. Is there any smoke on start-up?

Best to run a scan if you can to see if there are any error codes on the plugs, or if you know they haven't been done since leaving the showroom consider changing them anyway as it is rather inexpensive.

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[BASSCUBE]

It has been scanned and couldn't find any faults. Just recently been serviced also.

Doesn't do it all the time just sometimes and only when it's cold.

Once it is warmed up runs as sweet as a nut.

Surely an injector or glow plug would bring a fault up though?

PS: No smoke.

[Roy_01]

It will not always throw up a fault code, only when it's beyond a certain point/limit.
A bad coolant temperature sensor can also be a cause.
If you are having the cold start problem even in summertime >21 degrees Celsius it would be more likely the injectors or coolant temp. sensor. Because the glow plug pre heating shuts of when the coolant is 21 degrees Celsius.

[BASSCUBE]

Hmmm interesting.

Why isn't it hesitant when driving ? Surely if a blocked injector it would be lumpy and erratic all the time?

coolant temp sensor could be it.

[lewisheywood]

Did you sort it in the end ?

Out of curiosity

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[LLD123]

Interesting thread as my other half has a Skoda Octavia Vrs and that’s got the same engine in as the sciroccos. He also has starting issues occasionally mostly when cold. Also haven’t got it fixed yet. We changed the coolant temperature sensor at the weekend. It now starts on the second time compared to starting on the third time so hasn’t completely fixed it but is better. However when the car is warm is starts fine. Again couldn’t find a fault code for it either.


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[Keagan245]

Hi guys, I’ve been having several issues with my 2010 2.0 Tsi roc. Firstly the car idles very rough, it still maintains 760+ RPM at idle. The roughness is less noticeable while in neutral however as soon as I put the car in P,S or D the roughness becomes a little more aggressive. I’m sitting at 90000 Km’s and the car was recently given a Major service in which the gearbox mounts were changed. The roughness only started after the car came back from the dealership. Could this be caused by the new mounts? I assumed it was normal and so a few weeks later I put an induction kit along with a downpipe and racechip ultimate in the car as well as an upgraded DV. Everything worked fine until 2 months later when I kept on getting P0304 and P0299 codes. Took it back to the dealership, replaced spark plugs and put in new R8 coil packs. The misfire is gone however I’m still getting a P0299 code. When accelerating, the car stutters around 3000-4500rpm in D mode with the power pulsing however none of this is noticeable under hard acceleration. The car on occasion starts but idles roughly and then dies out when cold or warm but starts up normal when tried again. I’ve removed racechip but the symptoms still persist.

What could be causing the stuttering of power and the P0299 code ?
What can be causing the car to cut out first time as it’s becoming increasingly frequent?

[blower]

In terms of the harshness (I assume vibration) being felt through the cabin, after the gearbox mounts were changed:

This is commonly caused when the engine/gearbox has not been re-seated correctly. In particular the mount in the subframe where the dogbone/torque arm from the gearbox sits, must not be under any tension/pre-load when the car is idling. Commonly people will just support the gearbox, take the mount out and bang a new one in....unfortunately this can lead to the new mount not being aligned correctly and effectively pushing or pulling the gearbox back or forward a bit - putting preload on the lower subframe gearbox mount.

What you then feel is vibrations as instead of the dogbone mounting point sitting in the middle of the rubber mount, its vibrating into the sides - this vibration then transmits through the subframe and into the chassis. This is particularly noticeable when you put it into drive, as the gearbox will vibrate more and transmit this vibration through the preloaded subframe mount.

As for the other problems i'll let someone else answer that as that can be looked up....the above bit of info i'm sure hardly anyone knows about - including VW tech's.

[blower]

Ok, P0299 - Boost Pressure Regulation: Control Range Not Reached

You probably have a boost leak, this will either be a boost hose that's split or loose...or possibly your new DV has failed with a split diaphragm, which I wouldn't have thought so since I assume its the upgraded one (as in latest version genuine VW part and not some aftermarket one).

Either way check your boost hoses from the turbo to the intercooler and back to the throttle body. Also check that DV, take it off and take it apart to check the diaphragm.
Also check the hoses to the N75 solenoid valve.