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Misfire Code P301

266 Views 5 Replies 4 Participants Last post by  75aces
Hello, I have a 2005 Corolla LE with the 1zzfe, it has 191k on it and I’ve recently gotten a very bad misfire. P301, and stated by the reader I replaced the plugs, which had oil on them, replaced the valve cover gasket and tube seals, with the code remaining. The code then shifted to a misfire on Cylinder 4 which was fixed by swapping Cylinder 1’s ignition coil and replacing the faulty coil with a new one. Code still reads a misfire expect now it’s for Cylinder 1. Checked fuel injectors and none of the seals are cracked, idles rough, no smoke out of the exhaust. Please help if you have any advice that is also greatly appreciated!
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マズダスピード3
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Put cylinder 1 at top dead center. Then verify that the timing marks on the crank, intake and exhaust cams are aligned with the markings.

It’s possible that your engine is skipping timing.

The other possibility is that you have a dead coil pack. Even if you swapped coil packs, you need to test spark to verify that the plugs are firing.

As suggested, perform a leak check and compression check to ensure you didn’t lose a cylinder.
 
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Discussion Starter · #5 ·
Is the maf sensor / coil packs plugged in ?
MAF sensor was replaced 5k miles ago, cylinder 1’s coil thread has been stripped so going to tap and die it to get the bolt to sit in correctly, also will be ordering the remainder of ignition coils to cancel out bad coils since I’ve only replaced cylinder 1
 

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MAF sensor was replaced 5k miles ago, cylinder 1’s coil thread has been stripped so going to tap and die it to get the bolt to sit in correctly, also will be ordering the remainder of ignition coils to cancel out bad coils since I’ve only replaced cylinder 1
Is the MAF sensor a denso or oem? Did you replace the o ring at the same time? Did you attempt to clean the original maf with maf sensor cleaner?

Need to inspect the intake tube for cracks. This may be causing the misfire or contributing to it.
 
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