2013 Prius Two with 200k, well maintained (all "standard stuff": ATF, coolant, PCV valve, oil, Top Tier Gas, etc) SUDDENLY getting engine knock on startup, and also when re-engaging the ICE (ex sitting at stoplight, then hit the gas). Blue Driver now says: P0302 I have only 1 day to attempt repair for an upcoming trip (otherwise take a different car). What are the most likely things it could be, and how to rank them? Here are my current guesses: (1) Given the generally good maintenance done on the EGR CIRCUIT [2]+[3], AND IF THE PROBLEM LIES THERE, the most likely would be a stuck EGR Valve? (BUT IS A STUCK EGR VALVE LIKELY TO THROW A P0302 SUDDENLY?) (2) Bad ignition coil? (never replaced/200k mi now) (3) Bad spark plug? (but replaced 45k ago) (4) Bad fuel injector? (but run Techron every 2k mi) What to try first? Anyone recall a similar post where the KNOCKING STARTED SUDDENLY? MORE DETAILS [1] (0k ago)/200k Examined EGR Tube and Intake Manifold (no appreciable buildup)(as expected given [2]) [2] (20k ago)/180k NEW EGR Tube, OXI-Clean Intake Manifold, Cleaned Throttle Body, Cleaned MAF [3] (45k ago)/155k NEW EGR Cooler, Brake Clean of EGR Valve, new spark plugs, new PCV [4] 12 oz Techron every 2k [5] NO Oil Catch can (OCC) [6] Coil Packs: NEVER CHANGED [7] No coolant loss or oil fouling (0.08qt/1k miles oil loss typically) Thank you!
You need to pull up YouTube video on how to diagnose a misfire. Move the plugs move the coils clear to code see misfire moves with plug or coil. If not pressurize the cooling system with the plugs are moved Wait crank the motor see if anti freeze blows out the plug hole
Open up the engine coolant reservoir and see if it sucks air in when opened. If it doesn't your headgasket is likely ok. If it does, your headgasket failed and is burning coolant. Some people can go years with this failure, but if you go too long you can damage dampener in transmission from rough engine running.
Check for real if it is head gasket issue. P0302= cylinder 2 misfire. You can check by swapping the plugs and coil from cylinder 3 or 4. If it does not move to p0303 or p0304, then it is cyl 2 problem. Do not let misfire for too long, it destroys Catalytic converter = $2000 job. If the leaks is so small, you can either test it with endoscopy and pressure test the coolant line.
