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Check engine light flashing with codes P0301, P0303, P0300 and P1399

Tiny
GORDON2
  • MEMBER
  • 1998 HONDA ACCORD
  • 2.3L
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 256,000 MILES
My car has been running rough recently and I thought it was having trouble shifting. It has been inconsistent. Today the check engine light started flashing. I have 3 confirmed codes and 1 pending code. The confirmed codes are P0301 [Cylinder 1 Misfire Detected], P0303 [Cylinder 3 Misfire Detected], P0300 [Random/Multiple Cylinder Misfire Detected]. I have a Pending P1399 [Manufacturer Defined] code. Where do I start?
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Thursday, May 13th, 2021 AT 5:40 PM

2 Replies

Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Good evening,

I would start with the basics. Replace the plugs and I would also check the compression to be sure the timing is correct. You should have 140-160 pounds.

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

https://www.2carpros.com/articles/how-to-test-engine-compression

I would also check the fuel pressure low pressure from a bad fuel pump will cause these misfire codes.

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

Roy

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Thursday, May 13th, 2021 AT 7:04 PM
Tiny
JIS001
  • MECHANIC
  • 3,408 POSTS
With the mileage on your vehicle I would strongly recommend a valve lash adjustment. Normally the exhaust valves get too tight and hold the valve open too long where you will get the random misfire. You will also see it in the fuel trims being in the negative number indicating too rich.

The valve adjustment needs to be done when the engine is at room temperature. If you need instructions let us know and one of our colleagues will post it up.
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Thursday, May 13th, 2021 AT 11:15 PM

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