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Any mechanics that can help diagnose this?

I have a 2011 Prius. A month or so ago I got a P0301 code and replaced the spark plugs and ignition modules. It ran fine until today when it started misfiring again and again I have a P0301 code. I’ve also noticed that while in Park with the gas to the floor the RPMs rise and fall while my foot stays hard down. I also noticed an ethylene smell in the cabin when it started misfiring. Also, starting from a stop it misfires a bit, but once up to speed it’s fine. Before I start going to the next thing I can think of, which is to clean the intake manifold and EGR valve, do you think that would even be the issue? If not, then what?

Edit: it only misfires for a few seconds before going quiet again, even just sitting in park

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DownTheStreet · 56-60, M

@Zaphod42 I don’t know how the Prius engine is laid out but check the ones you’ve put in since. You’re sure of the basic stuff like the plug wires being in damaged and connected firmly in place at both ends? Does it misfire at all rpm ranges?

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Zaphod42 · 51-55, M

@DownTheStreet Near as I can tell they’re ok. It’s a wire harness, so I can’t see the length of them, but they’re fasted securely anyway

GeniUs · 56-60, M

@Zaphod42 Quick trick I found by accident; run the engine with hood up in the dark, any shorts/cable problems show themselves (blue light /sparks). Just a quick way to spot anything like that but does not guarantee that the cables aren't faulty. (If that makes sense).

Zaphod42 · 51-55, M

@GeniUs That makes sense! If I don’t have this fixed by dark I’ll try that

senghenydd · M

According to my book of codes PO301 is cylinder 1 misfire, so maybe you could check-out cylinder 1

SubstantialKick · 36-40, M

How about your coil packs? That's the next thing I would consider.

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uncalled4 · 56-60, M

@Zaphod42 Sometimes, you have to go OEM or the computer no likey.

Zaphod42 · 51-55, M

@uncalled4 Yeah, learning that, lol. Just got back from the parts store…unfortunately they only had two coil packs, but since it was originally just cylinder 1 and just now #2 also, I’ll replace those two and see what happens.

uncalled4 · 56-60, M

@Zaphod42 I had to put 2 alternators in my Acura before I got an OEM. Turns out I didn't even need to do THAT, because bearings had seized in the harmonic balance, which I found out is not unheard of in the 2.5 engine(old Vigor model), so the belt was spinning but the balance was frozen. Eek.

checkoutanytime · M

Why? A prius 🤭. Toyota is the best, but a Prius, cmon dont be a better then anyone else kinda person. They are specifically designed for dumb people.

Luminoussoul · 36-40, M

Check igniter coils/cables of sparkplugs

Zaphod42 · 51-55, M

I replaced the coils when I did the plugs. The wires harness for it is a while other thing…hope that’s not the issue @Luminoussoul

Luminoussoul · 36-40, M

@Zaphod42 check the wiring of igniter coil if it is ok then go for fuel injectors

DownTheStreet · 56-60, M

What did the plugs look like when you pulled them? Fouled?

Zaphod42 · 51-55, M

@DownTheStreet Dirty and old, but no build up on the points

Iwillwait · M

Coil packs are bad most likely.

Zaphod42 · 51-55, M

@Iwillwait I wish! I changed those last month along with the plugs. Today I even got two more and replaced the #1&2 cylinders where the codes listed. No help. I’m down tonight either being the intake manifold or the injectors

Iwillwait · M

@Zaphod42 just do them all.

uncalled4 · 56-60, M

Wonder if the ECM itself could be causing issues. I've run into that.

Zaphod42 · 51-55, M

@uncalled4 That’s a terrifying thought

uncalled4 · 56-60, M

@Zaphod42 Expensive

uncalled4 · 56-60, M

@Zaphod42 Hey, I might be looking at replacing my cats. Pft. But it might be ECM ghost codes.

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