MK5 Golf rough idle following start

[benpaul12 62]

No more BMW  have bought a 2005 Golf GT - was the only decent thing available at a good price, BMWs were either too old or too expensive! Anyway...

One day after buying the car (from a dealer) the engine light came on. As it's under 3 month warranty it went back, it was due to the knock sensor which has been reset - engine light hasn't come on again (had it for a few days now). 

I had a feeling that the engine light was tripped because I put 98 in the tank - perhaps this shocked the car after probably running on 91 fumes (good-damn dealers). 

While the engine light was on the idle after starting up (cold) was rough. After getting underway the car is fine and does not rough idle at all. This was resolved when I picked up the car. However, this morning the rough idle following cold start has returned. The rev counter isn't bouncing around, it's more of a car shake - feeling like misfires.

Looking around on forums this sounds like a difficult issue to diagnose, and many owners say it's common - and not actually a problem. Something you just have to deal with.

Has anyone experienced this or have any ideas? I am in a position where a non-diagnosed issue which is not easy to fix is difficult to argue when taking a car back to a dealer. 

[HaNs 226]

Need a diagnostic scan, drop it back to the dealer and ask for a loan car until the issue is sorted 

[benpaul12 62]

Thanks, it is going back in next week. I have a feeling this will be interesting.

[kwhelan 241]

those motors are notorious for vacuum leaks, and maf issues, there was also various recalls for the ignition coils so find out if theyve been done, just be really careful they don't start just replacing parts because the scanner says so, make sure you get someone who knows them well or you will just keep throwing money at it.

[benpaul12 62]

35 minutes ago, kwhelan said:

those motors are notorious for vacuum leaks, and maf issues, there was also various recalls for the ignition coils so find out if theyve been done, just be really careful they don't start just replacing parts because the scanner says so, make sure you get someone who knows them well or you will just keep throwing money at it.

As it's under warranty from the dealer (3 months) they will probably try and fix it in the most cost effective manner - but again, that could also equal not fixing the problem at all

[benpaul12 62]

Picked up today, they've replaced the NOX sensor and the coils. Hopefully it's all sorted now  - feels much better.

[Allanw 1071]

Google how much those NOX sensors are ;-)

They must have found a used one somewhere :-)

[benpaul12 62]

2 hours ago, Allanw said:

Google how much those NOX sensors are ;-)

They must have found a used one somewhere :-)

haha yes I have seen how much they are! Parts came ex Germany so maybe they did go for new?!

[Allanw 1071]

15 minutes ago, benpaul12 said:

haha yes I have seen how much they are! Parts came ex Germany so maybe they did go for new?!

Cool! Should last a while then!

 

Only some models use the NOX sensor.

[benpaul12 62]

Just now, Allanw said:

Cool! Should last a while then!

 

Only some models use the NOX sensor.

Tell me more? How come only some models do?

[Allanw 1071]

Ha - I replied to your thread on VASK too - just clicked... even though your name is (almost?) the same :-)

Different versions didn't. My Touran had the BVY engine (same basic engine as yours) but different emmissions gear. I think it was different on the later models mostly? There were some running issues with the Stratified mode, which my Touran doesn't use (although it doesn't have the 2.0 FSI now... it's a 3.2 )

 

[benpaul12 62]

Interesting. Before you upgraded it, how did you find the reliability of the engine etc.?

And yes, it is I.

Edited February 10, 2017 by benpaul12

[Allanw 1071]

Yeah, it was OK - I didn't have the 2.0 for long though.

[benpaul12 62]

Funnily enough I took it back to the dealer this morning as the light came back on and running rough again - misfiring. Let's see what they replace now.

[kwhelan 241]

Feel your pain, had similar experiences with a VW turbo and a golf over the years, golf eventually had whole ECU replaced. They just seem to have too many sensors that can go wrong maybe with bad connections/voltages or something and too many emission hoses which get weird vacuum leaks

Oh the light is on again became pretty normal convo from her, I think changing all the coils and MAF 

I just don't trust audis VW anymore, got very tiring

[benpaul12 62]

^ Yeah I had a mk4 Polo and it was a dog's breakfast when it came to sensors throwing whoopsies. 

I'm happy that this Golf is under warranty, so the car will continue to go back until it's all fixed - if it keeps causing problems it will just have to go back... lol

[benpaul12 62]

Had it back for 2 days now and running much better. 2 coil packs replaced in total (1 more in the recent drop off). This has solved the misfire during normal running (so far).

The engine doesn't feel amazing after a cold start, but isn't running anywhere near as rough as before. Someone on the VASK forum and other forums has pointed out that this is a very common issue on FSI engines that's resolved by a carbon buildup clean. Am going to live with this for the time being as apparently it doesn't improve anything else (performance, economy).