Codes P0303, P0304, P0305 and P0306

Tiny
ROLLINGTHUNDER59
  • MEMBER
  • 2011 TOYOTA 4RUNNER
  • 4.0L
  • V6
  • 4WD
  • AUTOMATIC
  • 68,000 MILES
Originally I had a P0303 code on my vehicle. I decided to be proactive and take the opportunity to replace all plugs and coils with brand new ones that were exactly the same types - both Denso. After replacing, the vehicle ran fine for a few days but then out of the blue on driving, the vehicle started to cough and sputter for 10 seconds or so then ran fine. Checked the codes at home and had 4 codes show up - P0302, P0304, P0305 and P0306. I checked for loose wires, hoses disconnected and found none. I did find a grounding point on the frame that I thought was the culprit since it was badly corroded so I cleaned it off. I checked the others and well and cleaned them. It ran smooth as silk for another three days and again out of the blue it started to cough and sputter for 10 seconds or so. Got home and checked the codes - P0303, P0304, P0305, P0306. It almost seem to be an electrical short somewhere but I'm not sure. Any ideas?
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Sunday, July 11th, 2021 AT 2:31 PM

1 Reply

Tiny
ASEMASTER6371
  • EXPERT
Good evening,

I would start by checking the fuel pressure. Low pressure from a weak fuel pump will cause misfire codes such as what you have. You can rent a tester at a parts store for the test. I attached the specs below for you.

https://www.2carpros.com/articles/engine-misfires-or-runs-rough

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

You can access the pump unit under the floor at the back seat. I attached the procedure and a picture for you.

https://www.2carpros.com/articles/how-to-replace-an-electric-fuel-pump

Roy

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Sunday, July 11th, 2021 AT 4:42 PM

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