incomplete combustion diagnosis

[janmike]

i have signs on my spark plugs that my engine is having an incomplete combustion (black carbon deposits). aside from not knowing the cause i am baffled that most of my spark plugs suffer the same condition except for my no. 4 which is clean and (it seems as) showing a complete combustion! any ideas please?

[ghosthunter]

Few info first

What is your car. How old and mileage? What previous repairs (if any) has been done?

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You sure you aren't burning oil? Have you checked your oil level lately? Maybe a compression test would solve some light?

[[archie]]

^^ +1 parang may pumapasok na oil sa chamber. usually if the tip of the spark plug is black then its burning oil.

[janmike]

no oil..just dry carbon deposit except for 1 plug. its an old 2T engine btw

[ghosthunter]

no oil..just dry carbon deposit except for 1 plug. its an old 2T engine btw

definitely do a compression test.

[janmike]

been digging the net and i have read a few possible causes as to why. this include over rich a/f mixture(carb), ignition timing, valve leaks and intake manifolds including low compression. additional info is the engine eats up lotsa gas, carb obviously not in good condition, no knocking, pinging or hard starting, smell of unburned gas in exhaust, backfires on decelleration and loss of power on steep climb.



*ghosthunter
if bad compression is found would the engine require overhauling? TIA