I have a 2009 Toyota Highlander Hybrid (3.3L V6) automatic transmission with 206K miles. It was misfiring, and I drove around for about 5K miles with a P0300 (multiple/random misfires) and occasionally it would throw the code for specific cylinders but it wasn’t consistently throwing the same cylinder. I changed all my spark plugs and coils, cylinder 3 plug had some oil on it, the others just looked worn out. I have run Premium (91 octane) for the last 2 tanks (owners manual says 87 is fine) trying to do a form of Italian tune up, I’m not getting misfiring anymore but now I’m getting P0420 (low catalyst efficiency) and P2196 (stuck running rich). Could this be related/residual from driving too long with the misfire? Is there anything I should do/change, or will it clear up on its own?
I drove around for about 5K miles with a P0300 ... now I’m getting P0420
yeah big mistake. Flashing engine light means FIX ME NOW
I have run Premium (91 octane) for the last 2 tanks (
Premium fuel will do absolutely nothing for you.
Injector cleaner might.
If you have an oil-fouled plug it's time to do a wet vs. dry compression test on that engine to check for worn rings.
