2008 Prius w/186k. Long time lurker on the site, and have learned a lot here. I can't figure this one out, despite searching and reading dozens of threads on similar issues. My engine misfires/shakes at idle, runs fine off-idle. Codes P0300, P0301, P0302, P0303, P0304, no other codes. It is worse when it is cold. It doesn't lose any coolant, no coolant in the oil. Things I've done: -replace plugs & coils (OEM) -check head gasket using the tool w/ fluid that changes color when exposed to exhaust fumes -checked compression, all within specs -replaced fuel injectors (OEM) Not sure where to go from here. I'm looking for suggestions or experience with similar issues and what resolved it for you. I read this thread: Gen 2 Prius vexing idle/missing problem | PriusChat The inverter is something I haven't changed yet, but I have no inverter code. The symptoms are very similar to what I am experiencing. I don't really want to keep throwing parts at this thing. Any help is much appreciated!
I'm guessing if you replace the injectors you already cleaned throttle body and mass air flow sensor? Also have you rebooted all the engine computer settings by disconnecting the 12v battery for a few minutes? Also being super low on engine oil creates vibrations in crankshaft that triggers misfire error codes. So might want to figure out some ways to look into the overall health of the bottom end.
Yes, injectors were replaced with OEM. Cleaned both the MAF & throttle body. Oil is full and the car has never been run low on oil. Agree that it's almost definitely a vibration causing the misfire code. I'll try disconnecting the battery, but I'm skeptical that will fix anything. Thanks for the suggestion!
I would be looking at data on a scantool- specifically what short and long term fuel trims are doing at idle, and then while at cruise. I would also "add fuel" to the engine at idle to see if it affected the misfire. You could use a propane "enrichment" tool to feed propane into the air cleaner inlet- a propane torch might work but doesn't flow much fuel. Another possible cause could be a valve problem. A broken valve spring or valve intermittantly not seating can cause a miss but have good compression readings. An old fashioned vacuum gauge connected to intake manifold source such as the hose to the purge valve can help. What were your compression results for each cylinder? Posted via the PriusChat mobile app.
If you've done all these things and never disconnected the 12v battery to reset all the engine's settings yet, I suspect that's going to resolve it. Every time I've done same kind of work on a Prius engine it runs like it's going to die unless I reset everything by disconnecting the 12v.
@mr_guy_mann, compression results: 1 - 125 2 - 127 3 - 125 4 - 128 I had the valve cover off to do the gasket and the fuel injectors and I didn't see any valvetrain issues. I guess it could be a vacuum leak, though I would expect to get a lean DTC if there was. @PriusCamper unfortunately disconnecting and reconnecting the battery after about 30 min made no difference. I noticed today that the issue only occurs at idle when the multifunction display shows that the ICE is charging the hybrid battery. When it isn't charging the hybrid battery, it runs smooth. Any idea what that might indicate?
Roaming misfires is usually blown bottom end of motor. Main bearing has failed causing subsonic vibration. Or on a g2 usually piston. This engine likes throwing the #2 piston out the side of the block. Vibration distorts the pg waveforms from cam & crank sensors and The engine ecu gets poor waveform signals it cannot decode so defaults to random multiple misfires. Very common. Usually from poor oil maintenance. Tough little motor just has to have all its oil or the motor has had the shit beat out of it. put engine in inspection mode so it idles nonstop then crawl under the front of car and listen to the bottom end. Should be pretty definitive under there. Go on YouTube look up. PRIUS INSPECTION. Lots of engine replacements on this forum.
Back when I owned a vehicle that required a propane enrichment tool as part of its carburetor adjustment procedure, I found I could unscrew the restrictive orifice from my basic hardware store propane torch, and that made the flow adequate to the job. It is good to remember to put the orifice back in before using it as a torch again.
I doubt this is the issue. I've had it in inspection mode using Techstream and investigated (listened to) both the top end and bottom end. The noise is intermittent, and sounds like it is coming from the trans or flywheel. The engine runs smooth off idle and at idle when it isn't charging the hybrid battery. I've never met a main bearing or rod knock that got better (quieter/smoother) with higher rpm/higher load.
I doubted bottom end failure on my well maintained 2008 too, my misfire problem sounds very similar to yours, but was only on 1 and 3. Mine intermittently rattled/shook at idle, it would idle fine if I feather touched the gas pedal or put it in Neutral, both I assumed disengaged the load of the inverter/charger generating power. 4 refurb injectors seems to have fixed the problem, but I also cleaned the TB and MAF. The fact that you replaced most all of the items and that all 4 of your cylinders are reporting misfire should point to something common to all. Assuming it isn't the ECU or wiring or ground problem, could it be a failed fuel filter that fouled all of your new OEM injectors?
