Codes PO300, PO301, PO305

Tiny
CORY2427
  • MEMBER
  • 2012 VOLKSWAGEN BEETLE
  • 2.5L
  • 5 CYL
  • 2WD
  • AUTOMATIC
  • 95,846 MILES
It is saying random multiple misfire and cylinder 1 and 5 misfire, but it runs like it always has. Doesn't seem anything is wrong. Hard to start sometimes. Replaced plugs on it bout 500 miles ago. Just worried because engine light on.
Tuesday, October 1st, 2019 AT 1:18 PM

9 Replies

Tiny
STEVE W.
  • MECHANIC
  • 13,414 POSTS
Welcome to 2CarPros. P0300 is random misfire and is likely the result of the other two misfire codes. What did you use for spark plugs? OEM or? There are a lot of fake plugs on the market these days and they can fail rather rapidly. What I would do is swap the plugs to other cylinders and see if the misfire follows them. So put plug no.1 in 2 and no. 5 in 4 and see what it does. If the misfires move then I would source a new set of OEM plugs and install them. Misfires can rapidly destroy the converter because of the raw fuel from those cylinders. If you swap them and the misfires stay in the same places then I would swap the coils in the same way and check the wiring for the coils. The connectors are known to loosen and then you need to replace the connector ends.
But moving the parts first is a quick way to test them without spending money.
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Tuesday, October 1st, 2019 AT 8:44 PM
Tiny
CORY2427
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I put oem's in it but I reset the codes in it yesterday. I’ve driven it probably 30 or more miles light has not came back on. Should I still be concerned or has it fixed itself/
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Wednesday, October 2nd, 2019 AT 6:43 AM
Tiny
STEVE W.
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It sounds like you have an intermittent issue. If the light stays off you may be okay, I would scan it a few times just to see if there is a pending misfire code. Some codes take more than one cycle to set. A pending code would likely mean you have a loose connection. I don't know if that tool would show live data for misfires on a VW or not, if it did you could see if it shows any misfires while running below the code setting threshold.
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Wednesday, October 2nd, 2019 AT 9:55 AM
Tiny
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What do you mean intermittent issue? No my tool does not do live data nut id say I have driven it 60 or more miles is not showing anything on freeze frame data or no pending codes or anything.
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Wednesday, October 2nd, 2019 AT 11:18 AM
Tiny
STEVE W.
  • MECHANIC
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Intermittent in that it isn't a constant problem. Something like a loose connector pin on a coil that vibrates just enough to cause a misfire or some dirt in the fuel system that momentarily blocked an injector(s) or more commonly a wire that shorts out once in a while. Any of those could cause those codes, the problem is that finding where the issue becomes much harder if it's not happening all the time. I'd just keep watch on it.
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Wednesday, October 2nd, 2019 AT 12:38 PM
Tiny
CORY2427
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Fuel filter could be cause? Where is it at on these models?
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Wednesday, October 2nd, 2019 AT 2:01 PM
Tiny
STEVE W.
  • MECHANIC
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Not as likely as an electrical issue. That's the issue with an intermittent, it could be anything but no way to tell if it only acts up once in a long while. However if the filter hasn't been changed it isn't a bad idea. To change it you need to pull the fuel pump fuse and let the engine shut down as the pressure drops. Then locate the filter back by the fuel tank. The bracket bolt gets removed and the lines get disconnected. Then the new one is installed.
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Wednesday, October 2nd, 2019 AT 2:54 PM
Tiny
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So I went to change the fuel regulator and noticed it said 4.0 bar. The new one I got is identical but is 6.6 bar. What’s difference or will it hurt it using it?
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+1
Friday, October 4th, 2019 AT 10:08 PM
Tiny
STEVE W.
  • MECHANIC
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The OEM spec is 4 BAR. The higher pressure shouldn't be used as it will change the fuel flow through the injectors.
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Saturday, October 5th, 2019 AT 5:33 AM

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