2.0 over-revving..?

[terri8le1]

Hi chaps.

Got a couple of things bugging me with my 02 2ltr GTI. Firstly, its just started over revving when i put my foot down after changing gear and going nowhere..it sounds like i'm driving an automatic! Sorts itself out when I ease off the gas a bit..any ideas? Also, it only had a full service a few weeks ago but..seems to be running really lumpy, especially when cold..judders like its struggling to get the fuel in and seems worse below 2000rpm, once past that it seems to smooth itself out.
Any help would be great...thanks in advance!

[itavaltalainen]

Fault codes? Measuring blocks look OK?

[terri8le1]

I'm a bit of a noob as well if I'm honest sorry, what are the measuring blocks? Codes on the diagnostics were:

16684
16688
16686
16804
17704

[itavaltalainen]

You got a faulty thermostat, misfires on cylinder 2 and 4 and a CAT fault (probably due to two previous errors).

http://wiki.ross-tech.com/wiki/index.php/17704/P1296/004758
http://wiki.ross-tech.com/wiki/index.php/16686/P0302/000770
http://wiki.ross-tech.com/wiki/index.php/16688/P0304/000772
http://wiki.ross-tech.com/wiki/index.php/16684/P0300/000768
http://wiki.ross-tech.com/wiki/index.php/16804/P0420/001056

So check ECU and dash measuring blocks (http://www.ross-tech.com/vcds/tour/m-blocks.html) to make sure it's thermostat and not coolant temperature sender. Then replace faulty part.

Check the ignition coil (or coils if you have individual packs) as well as HT leads and spark plugs.

[terri8le1]

Ok thanks for that! I assumed spark plugs and HT leads would have been replaced when I had it serviced? So I cant really do too much myself to sort it, I don't have the equipment to check the ECU etc...Guess i should get it booked into the local garage. Also forgot to mention the engine management light has been flashing occasionally when cold..goes off once warm. I know that can mean a number of things but thought I'd mention it. So what do you suggest the over revving is again? 

[itavaltalainen]

Well if a cylinder or multiple cylinders are not firing you have too much oxygen in exhaust gas, which gets picked up by lamda.... ECU injects more fuel to correct.

Spark plugs will only have been changed on your request unless they were due to be changed. On a mk4 most likely they have not bothered unless you told them to. It should tell you on receipt what they changed.

HT leads don't get changed at a service ever, unless faulty and then you'd be charged for them.