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.
Quite frankly, I would hope this engine is not an excessive oil burner, has not overheated while continuing to drive or does not have a bent rod or warped head. Otherwise... Hopefully it was an oem or Denso maf. Others almost never work well. I would put the old one on as a test. You should focus on the parasitic draw, assuming it is real, since it could also lead to your misfire problem. First thing is to actually measure the parasitic draw. The car has to be off with doors and hatch closed for about ten minutes. Series connect an ampmeter function of a multimeter at the negative battery terminal, remembering the hatch must be closed after hook up. If it is a major draw (maybe greater than 100 ma), isolation with millivolt readings across fuses may be possible. The chart below shows how much of your measured parasitic draw is coming from a given fuse. If this sounds difficult and you have little experience in this area, get help.
Did you check the block n head for warp? Check and compare piston height for slightly bent rods? You didn't replace the chain or tensioner, because there's undoubtedly some chain stretch @ 200K+ miles. A head gasket job; if done properly - should last more than 50K miles; so something is definitely off. Do a compression and leak-down test to see where you are on the engine repair. Chewed wires can cause weak spark; but if that was the case - accelerating the motor wouldn't settle-down the misfire, because your working the coils harder. Faster RPM = more sparks/min.. I'm leaning more towards a load issue, based on what was typed above. Don't get me wrong; the electrical issue still needs to be addressed - the real question is; how much time and money are you willing to spend on it? Just my 2-cents....
