Hello everyone, I'm hoping you all can give me some advice and steer me in the right direction. My car is a 2012 with 156,000 miles. My problem started with some shaking occasionally when the motor would kick on after starting or after being stopped while driving then it threw a P0302 engine code. Did some research and decided to start by replacing all 4 plugs and the coil boots and I also added a bottle of Techron when I filled up. Ran great for about a month then started doing the shaking again. The CEL came on again and this time it was P0300, P0301 and P0302. I swapped the 1 and 2 coils with the 3 and 4 coils just for the heck of it and cleared the codes. It now has a pending P0300 code but no CEL yet. Any idea of what might be going on and what would you all do next? Thanks!
The usual causes of misfiring involve fuel, spark, or compression. Looks like you've made some efforts to rule out the first two. Have you done a compression or leakdown test?
Have you heard of EGR cleaning? More info in my signature. Third gen head gaskets are failing with tedious regularity, around your mileage, typically cylinder one or two.
Well, I've had an extremely frustrating day. I spent about 9 hours working on the car. I removed and cleaned the egr valve, cooler and egr pipe, I removed and cleaned the intake manifold and throttle body and replaced the gaskets on both. I cleaned the mass airflow sensor and put everything back together. Started it up and immediately got the shaking but I drove it around the neighborhood for a while and it didn't do it anymore anymore. Parked it for a bit and took it back out. Started shaking and knocking again several times when accelerating and threw a P0302 code, so I'm right back at square one. What's my next step? Is this most likely a blown head gasket? My mechanic neighbor suggest it could be the fuel injector but I don't want to just throw time and money at guesses. I would be very grateful for any help here. I also have not done a compression test...is that something I can do myself? It's not something I have experience with.
Wow, you got a lot done in one day. I had some water left in my intake manifold after cleaning and rinsing it out with copious amounts of water after cleaning and scrubbing it out with Simple Green Pro HD cleaner. The car was knocking and shaking pretty bad when I started it up, but got no codes. Subsequently, there's no problems and no rough starts/running. Unfortunately, your situation sounds like you might have a head gasket failure with coolant leakage into one or more cylinders. The liquid/water in the cylinder(s) is causing the shaking at start up. The leakdown/compression test mentioned previously involves having special equipment/tester and an air compressor. Posted via the PriusChat mobile app.
Leak-down test is best for head gasket diagnostics. Requires compressed air, and a special gauge set. A little beyond typical DIY, but any competent mechanic should be able to manage it.
