Originally Posted by
foama
No rudeness percieved. I would be very happy if it were just bad gas, but that local company using half a dozen 3A90 Mirage has had each one repaired during the first year with the same trouble, and some have come back again. They drive short distances in town, and fill up locally.
I drive long distances only, and fill up at good brand stations wherever I need gas. Usually far from my home and rarely at the same place. Both cases same problem, only thing in common is the type of engine...
I will just have to wait and hope there will be no re-occurence.
In that case I reckon it has to be other of the two I mentioned: the PCV valve and/or a gasket problem.
Since your engine does not have EGR, the only other source of contamination that high up on the valves is PCV or gasket.
Of course, there is one other alternative: Someone hates that local company and has been dumping sugar is Mirage's they think belongs to them, maybe they mistook yours as belonging to that company. I doubt it though
I don't see natural accumulation of carbon happening this fast in such a small and efficient engine. The intake valves would be clean because of fuel spray. Worst case would be just the exhaust valves. Even back in the 40s and earlier, to have valves loose compression this early with those smokey bumbling engines was a rare rare sight. Doesn't make sense that today we'd see a problem that's virtually unheard of until you have put hundreds of thousands of kilometers on the engine. You're engine is just too young today, and even back in the ugly days, to have carbon build problems that bad. There would be other signs too: Smoke out the tail-pipe, degraded performance, rise in fuel consumption for the engine to output such amounts carbon in such a short amount of time.
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View my fuel log 2015 Mirage ES 1.2 automatic: 51.7 mpg (US) ... 22.0 km/L ... 4.6 L/100 km ... 62.0 mpg (Imp)