2012 Prius V 230,000 miles. New head gasket 55,000 miles ago. Just completed 2nd head gasket with new PCV, MAF sensor, cleaned both the EGR cooler and valve, cleaned out the intake and all it's passages, and cleaned the fuel injectors. I was careful with the timing chain install. Paid close attention to NutsaboutBolts and the Car Care Nut videos both the first HG change and this one. When I first started the engine in maintenance mode, it was rough for about 10 secs and smoothed out for about 5 minutes after that. It slowly started to misfire then all hell broke loose. Now it misfires with codes for cylinders 1, 3, and 4. Before the HG change this time the misfires were with 3 and 4 with bright white sweet smelling exhaust. It only is rough when in idle and park. Shift to neutral and it smooths out. Give it gas in park and neutral and it stays smooth. It's up on jacks - I put it in drive without gas and it's rough but not nearly as bad. I give it some gas and it smooths out. On top of this now I have a really bad parasitic draw where I can watch the voltage on a digital meter drop pretty quick. I disconnected the battery and it held the charge. There were mice in the car because it sat for several weeks when the weather was near zero or snowing. My kids leaving their left over snacks in it didn't help that. The mice were taken care of promptly but may have chewed some wires. I did try the EGR valve troubleshooting step from the Car Care Nut by inserting and securing a metal scraper between the valve and hard pipe flange. Sounded like it was going to solve it for a quick second but then really didn't change at all. Thanks all for your input. I used this forum quite a bit while trying to troubleshoot it. But I may have missed something. Thanks again!
The only change there is that 'idle' in park isn't always idle. The car can be charging the battery, which means the engine still turns at idle RPM, but under load. Shifting to neutral takes the load off. So this boils down to a misfiring-worse-under-load issue.
