P0300 Random Misfire - Toyota Nation Forum : Toyota Car and Truck Forums
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post #1 of 2 Old 04-05-2019, 12:46 PM Thread Starter
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P0300 Random Misfire

2007 V6 Limited, 120k.

Getting a P0300 (Random Misfire Detected)

Just replaced plugs, still getting the code. Is very noticeable around 1400-1800 RPM at 50mph.

Any help is appreciated!

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post #2 of 2 Old 04-05-2019, 09:30 PM
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Welcome to the forums!

Yer best bet is to perform a diagnostic read of yer ECU and sensors via the OBDII port with a decent/pro level scanner. Depending on what the scan sez, you might need to hook up an oscilloscope to git a better read on what might be causing the misfire.

Has this vehicle been in an accident before? Any other maintenance performed prior to this issue? Any aftermarket modifications installed? What make/model of spark plugs did you install? Do you have any piccies of the business ends of the previous plugs? Any issues with the old plugs?

I take it that you have the 4.0L, 1GR-FE engine? Have you inspected and cleaned the injector grounds? I'm not exactly sure where they would be on the 1GR-FE engine but on the 5VZFE engine they were on the air plenum. Have you been using Tier 1 fuel in yer vehicle? If not, you might want to run a decent fuel injector cleaner through yer fuel system. I really like the BG 44K fuel system cleaner. You might have a dealer near you or you can find them on eBay fer about $15 to $20 a can.

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