07 Prius misfire troubleshooting

which codes?

Don't assume the plugs are good, try a new one. Look for air leaks.

 

OEM or other name-brand plugs are seldom bad, but will-fit ones (private label etc) are ALWAYS suspect.

The fact that when you changed coils the misfire changed suggests that a coil or boot may be to blame.

Did you LIBERALLY coat the outside of coil boot and plug cavity with dielectric grease, did you use quality (Bosch, NGK, Denso) plugs? If not, I would start there.

 

Suspect the coils, while the plugs are out swap the even coils to odd and vice-versa. If the DTCs follow the coils, BINGO!

 

if moving the coils around doesn't change anything with the new spark plugs then check the wiring loom, you may have a broken/frayed low voltage wire leading to the coil.

 

wow, them are bad. what kine?

 

They are NGKs from the photo, were also drowned at some point and with one broken insulator, that explains it ALL.

 

I would like to share my case of 2007 Prius misfire. It is a beat up 2007 Prius with 200k+ miles, previous owner did worse to maintenance this car. missing screws everywhere....., I changed HV battery with AGM 12V battery, and It had been working for me for 1 year.., I changed motor oil 6 weeks ago with mild oil spilled and some oil get inside of spark plugs, after 2 weeks, car was having misfired with car shut down suddenly with Codes 301, 302, 304 , It happened often with raining day, all ignition coils with condensation water, cleaned water out and it worked fine for few days and misfired come back with condensation water on ignition coils, broken head gasket? no, it is loosing spark plugs, Its small fume causing condensation water and it caused arcing and misfired. After cleaned all ignition coils and spark plugs, installed spark plugs with anti-seizing cream, car works fine again/

 

It’s quite a case.

 

My 2007 with almost 180,000 started bucking and felt like the engine was going to come out. Fortunately, i was only a few blocks from home. I put my analyzer on it and it showed the P0300, P0302 and P0304 codes. My first step was to replace the spark plugs, at about $9 each. A very simple operation after you move the relay panel to the side and assuming you have the proper spark plug socket and a 10mm socket to remove the coil packs.

After the new spark plugs were in place, same thing, bucking a kicking. Same trouble codes. At the suggestion of a friend, i switched the coil packs in pairs. Switched 1 & 2, and switched 3 & 4. I really expected the error codes to switch to P0301 and P0303, but was surprised when they switched to P0301 and P0302. Very confusing.

Next, I ordered new coil packs. I opted for the inexpensive Chinese ones, a full set of 4 was only about $55, vs that much each for the Toyota OEMs. I replaced 1 & 2 first, since they were the ones with the error codes. Voila!! The engine purrs like a kitten and my beloved little Prius is back on the road. By the way, I went ahead and replaced 3 & 4, but kept (and labeled) the old ones in case I need them in the future.

Hope this helps someone. I did a lot of reading about causes and just worked from the lowest denominator up. Fixed it myself for just over $100!!

 

And it’s $100 down the drain and waste of your time. Cheapo cops will not last long. It’s Chinese junk. Same if you bought the plugs anywhere but the dealer counterfeit spark plugs are just a way of life now.

Many youtubes of misfiring G2s and cops fixing them.

 

Good luck with your repair. If it works for you- fine. But don't be surprised if something fails in the next year. As a mechanic I've wasted way too much time dealing with problems caused by cheap parts. For this I only use parts from Toyota or a name brand (Denso - NGK, etc) from a reputable supplier. Not ebay or amazon.

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