M40 oil problem

[Fraz06]

Hi all, my 1990 1.8 m40 has got some oil issues, i first noticed it when there was tiny bits of black oil coming out from the tailpipe when the car was running, i thought i should try and investigate this, firstly i checked the spark plugs and all plugs where black, next i done a compression test and found that all 4 cylinders had decent compression got around 10 bars, so next i took the cylinder head of and discovered that all the valves inc inlet ones where black and i also noticed that the top of the pistons have black deposits on them as well as small black oily deposits around all the cylinder bores at the top around 2cm deep from the top of each bore. Has anybody any idea what could be wrong as i really would like to cure this problem, hope it makes sense and thanks in advance

[SteMarsden]

Lots of carbon generally means that its running rich (or lots of short runs).

Have you checked that the air filter is clean?
Given it many long, hot runs?

(the 2cm 'clean' gap on the bore is where the piston ring reaches TDC and nothing to worry about)

Could this be something to do with one of the temp senders making it overfuel?
Someone will be along shortly with a more comprehensive answer.....


Edit: I have jusr re-read your OP and realise the plugs are black AND WET which means oil I think..... Could also be:
1. Valve stems passing
2. Rings blowing past.....