I've acquired a cheap 54 plate arosa with the 1.0 AUC. It came to me with a misfire on cylinder 3 and vcds showed codes 16684 & 16687 which are random/multiple cylinder misfire and cylinder 3 misfire detected. I followed the code scan with a compression test, with the engine stone cold and the throttle wide open the following results were obtained,
cylinder 1 (cam pulley end) 150psi
cylinder 2 145psi
cylinder 3 50 psi
cylinder 4 145 psi
given that information I skipped messing around with ignition components and pulled the cylinder head off, with the head on my bench there was no obvious damage to the valves unlike other cars i've seen with burnt valves. I proceeded to fill the exhaust ports with paraffin and the exhaust valve on cylinedr 3 duly started leaking onto the bench. i repeated the exercise on the inlet valves and 2 of the inlet valves were leaking (i forget which 2 but not cylinder 3). I then removed all the valves and there components, the inlet valves are all nice and shiny on the sealing faces, the exhaust valves are all dark and pitted and there are a few cracks appearing in the one for cylinder 2 so they look like they need replacing.
I also filled the bores up with equal amounts of paraffin, after 4 hours 1 and 4 have lost some, 2 & 3 have contained the majority, I knew some would be lost as rings never completely seal the bores and im not too concerned as the bores that have lost the fluid both provided good compression results so I'm happy the rings aren't causing the low compression on cylinder 3.
Now to the point of my post, for those who have stripped arosa engines that showed low compression is it just a case of buying 4 new exhaust valves and then relapping all 8 valves in again, the valve seats have some pitting but nothing I'd say is excessive? Another option for the compression is if the headgasket has failed albeit I'd expect to see low compression on 2 adjacent cylinders but the headgasket is the original vw item and the cars done 99k miles so it may have decided to fail but I can't see any obvious signs on the gasket.
I know the easiest option would be just to chuck a second hand engine in but there also an unkown quantity and I plan on giving the car to a family friend as her first car so my preference is to rebuild what I have but I know some cars just don't like having there engines rebuilt and are never the same after.