Rough idle VW golf 03

[MarkL057]

Hello!
More problems with this infernal car.
I have a 2003 vw golf match 1.6 16v.
It's had rough idle when engine warm issues for a while now. Replaced the o2 sensors and engine coolant temperature sensor (as indicated by engine fault codes) which has reduced how often it happens significantly.
However, it does still seem to be happening occasionally.
Once the engine is warm and the revs have settled to their warm running speed I seem to be able to set it off just by turning something electrical on. Ie. Wipers or lights.
It's quite rough and seems to drop to about 500rpm before bringing itself back upto a healthier 750/800 and repeats. Most oddly is if I turn the electrical back off it doesn't settle. Although it has been known to occasionally after some driving.
I'm happy to upload a video on YouTube to demonstrate this if wanted?
Any ideas?
Thanks. Mark

 

[Belle427]

Start by giving the throttle body a good clean with a carb cleaner spray, there will be some guides on you tube for this.
Next thing to clean if it has one fitted is the idle control valve, a little trickier than the above but not too difficult.
Have a good look around whilst your in there for any loose or split rubber hoses.

 

[Ricardus]

VW's of that vintage were plagued by dodgy coil packs, though if it had one chances are it would have been replaced long ago.
Could be worth a look if the other cheaper fixes dont work.

 

[MarkL057]

Thanks to both of you. Will look into doing this on my next day off work.
I'm in no way mechanically minded so excuse my ignorance but would any of those cause things to happen with the electrics. Noticed last night my headlights seemed to dim as I reversed into a bay. Could have been imagining it but power steering seemed heavier too. Could possibly be me being paranoid and imagining things though as I've had plenty of problems so far.
Thanks again.
Mark

 

[Burnerman]

think it would be a good idea to have the charging system checked out.....as you've no doubt read elsewhere, with the engine running you should see around 14.4v across the battery terminals, and not much less with the lights on.
Maybe the alternator cut in speed is low, so its not charging properly on idle?
Many engines lose a few RPM with an electric load applied - the alternator takes more force to spin it - but the idle control valve can often compensate by speeding things up a fraction.
John

 

[MarkL057]

Thanks will look into that too.
Some day I will have a fully functioning car! Seems every time I have something sorted two more problems pop up!
Mark