When I turn on the ignition of car, it shows the light of oil, battery and engine. Sometimes it tun off and sometimes stay on. When it turn off the car starts easily. when engine light stays on, car is just cranking. any idea what to check? I went to the mechanic and he couldn't diagnose the problem as car was starting normally. I have recently changed the alternator, spark plugs, head gaskit (as it was leaking and oil went to spark plugs as the car was keep cranking and was getting start to diagnose the mechanic opens the spark it was full of oil so he changed the head gaskit as it was leaking.) My car is Mitsubishi Lancer 1999 model.
When the ignition key is turned, the car will start checking all the systems for it's functioning. Your car is equipped with sensors that does the check, it always advisable to wait for 5-10 seconds before you crank up the engine. The lights will go off once the checks are complete. Once you start your car,most of the lights go off, just in case if the lights didn't off, start the troubleshooting,
I would suggest you to check your starter system,airflow sensor, oxygen sensor. They could be culprit