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Constant misfires and check engine light on

Tiny
KENNETH MACDONALD
  • MEMBER
  • 2011 MERCURY MARINER
  • 0.6L
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 102,000 MILES
Car has had spark plugs, coil and fuel injector changed plus a a good cleaning by the mechanic. The check engine light came back on. It seems to be a slight vibrate at idle and I think but not sure it misfires at idle and on acceleration.
Any ideas would be helpful.
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Wednesday, August 8th, 2018 AT 1:25 PM

15 Replies

Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Good afternoon.

Did you check the compression? Needs to be around 150 lbs.

Did you check to see if the PCM is commanding the injector to open all the time?

Did you check for any vacuum leaks?

Roy

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

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

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

https://www.2carpros.com/articles/how-to-test-a-fuel-injector
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Wednesday, August 8th, 2018 AT 2:04 PM
Tiny
KENNETH MACDONALD
  • MEMBER
  • 9 POSTS
The compression was 120 on cylinder six which the CEL keeps throwing up code 306. It went up to 140 after cleaning and replacing injector. I do not know about the PCM, if mechanic checked. How do I check the PCM?
They are no other codes stored or coming up only misfire cylinder six.
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Wednesday, August 8th, 2018 AT 3:52 PM
Tiny
ASEMASTER6371
  • MECHANIC
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You need to verify power to the connector for the injector with a test light with the key on.

Then hook up the injector and probe the other wire while it is running and see if the test light flashes. If it does, then the PCM is good. If it does not, then either the wire to the PCM or the PCM is the issue.

You cleaned the injector? How?

Roy
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Wednesday, August 8th, 2018 AT 3:59 PM
Tiny
KENNETH MACDONALD
  • MEMBER
  • 9 POSTS
The mechanic hooked up to machine. We replaced the injector on cylinder six.
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Wednesday, August 8th, 2018 AT 4:41 PM
Tiny
ASEMASTER6371
  • MECHANIC
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What machine? There is no machine to check the injector circuit. You need to do this with a voltmeter.

Roy
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Wednesday, August 8th, 2018 AT 4:47 PM
Tiny
KENNETH MACDONALD
  • MEMBER
  • 9 POSTS
He did cleaning as it was gunned up with carbon with a thing you hook up.
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Wednesday, August 8th, 2018 AT 5:01 PM
Tiny
KENNETH MACDONALD
  • MEMBER
  • 9 POSTS
He said he checked for vacuum leak.
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Wednesday, August 8th, 2018 AT 5:02 PM
Tiny
ASEMASTER6371
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Cleaning external is not cleaning it. It is the inside where the fuel goes that is the area that needs to be cleaned.

What about the wiring I stated? Did he check that?

Roy
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Wednesday, August 8th, 2018 AT 5:08 PM
Tiny
KENNETH MACDONALD
  • MEMBER
  • 9 POSTS
Will ask tomorrow and get back to you. Thank you for the help, will update tomorrow.
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Wednesday, August 8th, 2018 AT 5:09 PM
Tiny
ASEMASTER6371
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Sounds like a plan.

Roy
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Wednesday, August 8th, 2018 AT 5:10 PM
Tiny
KENNETH MACDONALD
  • MEMBER
  • 9 POSTS
Good morning Roy. Okay mechanic said he did a carbon flush, compression test on cylinder six was at 100, rest of cylinders were 160. Changed out fuel injector on cylinder six.
Said there were no vacuum leeks, did not check the PCM. Said low compression is a mechanical issue and it will need a repair on the cylinder head. Hope this helps. Any ideas welcome.
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Thursday, August 9th, 2018 AT 6:01 AM
Tiny
KENNETH MACDONALD
  • MEMBER
  • 9 POSTS
Also, it seems to drag on acceleration under load. This is my wife’s car so do not drive it much.
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Thursday, August 9th, 2018 AT 6:09 AM
Tiny
ASEMASTER6371
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Yes, the low compression is your issue.

Most likely a burned valve or piston. The head will have to come off and be inspected for the failure.

Roy
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Thursday, August 9th, 2018 AT 6:23 AM
Tiny
KENNETH MACDONALD
  • MEMBER
  • 9 POSTS
Thank you. Is it cheaper to buy new head or repair?
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Thursday, August 9th, 2018 AT 6:25 AM
Tiny
ASEMASTER6371
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Repair would be much cheaper.

The head is about $1,200.00.

The valve job is about $500.00.

Roy
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Thursday, August 9th, 2018 AT 8:11 AM

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