2010 prius 5 185xxx miles hello everyone! i've been using the forums for all my maintenance odds and ends, but now i find myself with my first, possibly problematic, issue. i popped a P0354 code on my way home the other evening. it's defined as "ignition coil "d" primary/secondary circuit. it made the engine run very rough, sometimes feeling like it was going to stall out. i put it into eco mode for the remainder of the drive and didn't experience the feeling again. flash forward to this evening. car was still in eco, and the check engine light had gone away, but then it did it again. luckily i was close to home and made it without further issue. i've ordered a new ignition coil, and plan on replacing cylinder 4. if that doesn't work, i'll pull the plugs and look into further issues. my question is, what might "other" problems be, and what possible scenarios should i be prepared for?
While you have the cowl and the windshield wiper tray apart you want to pull all four plugs and all four coils and look for the red color coolant or rust color on all the extensions of the coils the extension is the part that goes from the top of where the wire plugs up all the way down and touches the spark plug then look at all the brown streaks on your spark plugs then when you pull the plugs out of each individual hole you want to smell the tip that goes down inside the engine which is below the threads and smell and see if you smell antifreeze If you don't know what that smells like open your radiator and take a sniff or open the jug with the pink fluid take a sniff remember that smell get away from the coolant but the plugs in your hand and look at the tips of the plugs for little tiny water droplets they will not run together on the plug they will look like little drops of rain one or two plugs may have this generally not all four it's usually one and two plug numbers which start on the passenger side of the engine If you smell coolant or if you taste coolant on the tip of your plug that's how I do it with my tongue but that's me. If you have this then generally your head gasket is allowing the leakage of coolant into the combustion chamber and the coolant is trying to put the fire out prematurely and you get bucking springs bouncing on your equivalent of a flywheel springs popping out of that flywheel and falling into the transmission bellhousing and then the engine cracks on the back side and then it is useless this is what generally happens in the generation 3 world of Prius Good luck.
Not sure if toms covered it, but you could try switching the coils around, say swap cyl one and four coils, see if that changes the code. If it doesn’t, then it’s not likely to be a problem with the coils. Label them all before starting to swap.
