Rough idle and runs rough until it reaches thirty to forty MPH after which the check engine light starts flashing

2000 TOYOTA 4RUNNER
187,000 MILES • 3.4L • 6 CYL • 2WD • AUTOMATIC
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RUDY REYES III
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  • 2 POSTS
My vehicle has a very rough idle and when I take off it's very rough. When I reach about 30-40 MPH it's fine and runs smooth. However when I go past 40 MPH the check engine light starts blinking then it leaves a code. I read the code and it says cylinder 3 misfire. I changed all 3 ignition coils, wires, and 6 spark plugs. My fresh air intake hose was ripped so i replaced that too. I test drove it and still the same behavior. very rough idle and rumbling as I speed up and blinking check engine light when i speed up. I have no idea what else to do. Also I replaced all 6 fuel injectors about a year ago and replaced all the gaskets on the plenum. All this started happening after I changed the oil and oil filter. I have no idea why this is happening. Any help would be great. Thank you
Jul 3, 2020 at 8:45 AM
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ASEMASTER6371
  • ✓Experienced Mechanic
  • 52,796 POSTS
Good evening,

You have covered the basics but the first thing I would have done is check the compression when you had the plugs out. You need to verify there is proper compression for the engine to run correctly.

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

I would start there.

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

You can rent a tester at a parts store.

Roy
Jul 3, 2020 at 9:56 AM
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RUDY REYES III
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Thanks for the answer Roy. Should I test just the one cylinder that keeps misfiring? Or should I do all 6?
Jul 4, 2020 at 12:58 AM
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ASEMASTER6371
  • ✓Experienced Mechanic
  • 52,796 POSTS
I would do all the cylinders.

Roy
Jul 4, 2020 at 1:06 AM
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