Just stripping down the 205 engine out of my 185 after it died late last year.
It started 3 cylindering at idle & light throttles, noticed just after doing an event which was pretty tough on the engine - also very dusty although there was no sign of any split on the inlet side after the filter so probably not relevant.
The engine ran smoothly & pulled well at anything greater than light throttle, with no nasty noises. From the engine bay you could hear a slight tapping from the top of the engine (like large tappet clearance) on overrun only.
The problem was soon traced to No. 4 cylinder as removing this plug lead made no difference to idle, whereas the other 3 did.
A compression test showed as OK. No great crankcase pressure.
Tried the following, all with no effect:
New set of plugs.
Tried another set of good leads & dizzy cap from spare engine.
Tried another injector rail & injectors (& seals)
Checked for any leaks on anything near No. 4 runner on manifold.
Tried another inlet manifold.
Tried swapping No. 3 & 4 injector drive.
After a few thousand further miles the car deteriorated fairly quickly while I was away from home and became hard to start and a bit hesitant. Finally blew it's dipstick out and threw a load of oil out of the a-a scoop while overtaking in 3rd at about 70. I concluded it was ringland after all and the car hasn't been used since limping it home.
Started stripping the engine, and wasn't surprised to see a couple of scores in No.4, however the piston & rings appear OK apart from the corresponding score marks.
I'm guessing the scores are the result of foreign matter lodging between piston & bore and staying put for quite a while - they are quite deep.
Stranger was that No. 3 had the failed ringland. There are indentations on the top of the piston and in the head. There is build up of material on the edges of the indentations so I'm thinking this is the result of foreign matter rather than detonation. Seems likely that this caused the ringland failure.
I'm now suspecting the misfire and ringland failure are probably not related, but what would cause the misfire ? Next thing will be to strip that end of the head and check for broken valve springs, cracked valves etc.
I'm hoping to bodge the engine back together as a stopgap with a spare standard piston (I have a couple of sets) so it would be nice to find the reason for the misfire.
This was accompanied by a loud knocking noise and oil smoke from the exhaust.