P0300 Random / Multiple Cylinder Misfire DetectedCylinder 3 misfire

[dante2086]

P0300 Random / Multiple Cylinder Misfire Detected
P0303 Cylinder 3 Misfire Detected

My car was showing the check engine light. Took it for a diagnostics and those two codes came up.
The dude who did it didn't even touch the engine, and the light diappeared and he said the car was fixed.

1. Is that possible
2.If it isn't, then what could be wrong exactly and how can it be fixed.

[BLH]

May come back.
Most scanners have the ability to clear the codes and make the light go off.

[Bluevitz-rs]

do you hit the limiter a lot?

[dante2086]

No, I don't hit it that much.
But when the check engine light is on, I noticed it's easier to hit.
How the car detected the problem was when I was travelling.
I hit 120 kmph once, and the light flashed so I slowed down.
The light then disappeared, then when I hit that speed again, the light flashed and stayed.
I took it somewhere, and they reset it. Then when travelling back the light came back, the same way it did before.
Before this, my car hit 170 kmph without sneezing.

[Bluevitz-rs]

If the light is flashing you're possibly doing damage to the cat. It's a warning to let off the throttle or risk permanent damage.

Try running a few tanks of premium fuel and some injection cleaner through.