Please diagnose this problem.
My car runs fine on CNG, at petrol it was giving knocking sound, with unstable RPM. As recommended by mechanic and others i filled the tank with high octane to mix it with the remaining bad petrol in the tank. As a result now the car does not knock too much, the knocking sound reduced by 90%, now the car only knocks when i turn on the ac and push the race pedal hard. however the RPM remains still unstable, and at many times when Iam not accelerating or applying brakes the RPM goes to zero and car engine stops. Another big problem is the Car wont start in the morning and in the evening after 8-9 hours of parking. i have to waste at least 10-15 minutes of trying and then car starts with jerks, it feels like something is stopping the fuel to the engine.
Please diagnose this problem.
@capsat