Just thought I would share my experiences over the past few weeks. Basically, my 150,000m 1.8t seemed to be showing its age. Central locking was playing up, so was the fuel gauge. Idle started to get really lumpy, idle speed hunting all over the place and stalling quite often. Then to cap it all, week last Sunday morning the battery died on me. I was beginning to think it was getting past its sell by date.
First up was a new battery and a set of spark plugs. When fitting the new plugs, the first thing I noticed was 2 of the old ones had started to work loose, they were covered in oil. They were also really worn even though they were long life bosch ones. With the new plugs in the idle was better, but it was still hunting at idle.
Quite a few people have said that cleaning the throttle body can cure poor idle. Someone else recommended checking breather hoses as they are prone to splits causing poor idle.
I decided to tackle this on the weekend after I changed the battery\plugs and during the following week I realised that the central locking and fuel guage were now working properly which was nice.
Anyhow I bought some carb cleaner and on monday night stripped off the throttle body and gave it a good clean. It wasn't that dirty but what a difference it made. It now idles perfectly and as a result it is now much better to drive, back to its old self.