Mysterious cause of engine smoking - lateral thinking needed to solve
Suddenly noticed my 2.0 Twinspark engine smoking really badly, especially when pulling under power. Engine had done about 100 000 miles/160000kms, but was still sounding and pulling well. After having taken the top off, damage was noted in one cylinder. Piston was slightly burned and cylinder had a deep scratch. Had a complete rebuilt undertaken by professionals. New valves, guides, pistons, bearings, etc.
Shortly after receipt of the car: Again noticed smoke coming out of the exhaust. The smoke has an oily smell. Strange thing, while highly inconsistent, it is as if it is worst when idling. Really bad sometimes - similar volume of smoke to what I have seen in the past when squirting carburettor cleaning fluid into a running engine. Yet car starts, pulls and idles well. No smoke on start-up whether cold or hot. Sometimes when sitting in peak-hour traffic, or waiting for a gate to open, the smoke would almost engulf/cover the vehicle. And the next morning there would be nothing wrong on start-up.
Hoped that it would be something in the fuel. So drained that and filled up with fuel from a fuelling station with relatively new tanks and high turnover. To no avail. I have only covered about 600miles/1000 kms since rebuilt, and am unable to quantify how much oil is used.
The experts seem to be at a loss. Any ideas on what could be causing this? I am reluctant to take the car on a long road trip while it is trying to tell me something is wrong.