Excellent learning situation manifesting itself in form of : Impreza with warm engine cranks but doesnt start until some time (5-15 mins) has passed.
Its been happening intermittently in +20, 0 and -30 degrees of Celsius. By reading this wonderful forum found that probable cause could be engine coolent temperature sensor, I
replaced it with new one and cleaned crankshaft and camshaft position sensors from oil and dirt. Car ran much better and responded well to throttle, but it
didnt stop the problem.
Instead of replacing stuff I Want to diagnose stuff like a boss when problem occurs next time and be able to pinpoint problematic part. I removed passanger side metal panel from floor and found ECU with text 2G, 22611, AC540, A18-000 D15, 6212, Unisia Jecs Corporation , Made in Japan. Then I went to look for ECU pin order and found few wrong ones but photos from Ausubaru.com were promising.
Thanks for user jzk25 for these,
I tested TPS with usb-oscilloscope and laptop and it drew smooth curve as I pushed pedal.
Gonna later post screenshots of crankshaft and camshaft position sensor results. But I didnt get logical results from O2 sensor pins, if I recall they were something like
12 voltages but gonna verify pins and measure again to make sure. When I disconnected o2 sensor I was suprised that it didnt light CEL.
Could someone verify if this statement is true or does it apply in my case.
A faulty oxygen sensor can reduce your fuel economy by 30 to 40 percent and drastically reduce performance.