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Running bad and check engine light is flashing

Tiny
PENNY4146
  • MEMBER
  • 2005 GMC ENVOY
  • 4.2L
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 145,000 MILES
Check engine light was on and car just began to run bad. Replaced the crankshaft position sensor since the camshaft sensor was previously replaced. Still ran bad and check engine light was still on. It threw up a different code saying misfire on cylinder one. Checked the spark plugs and had a small amount of oil on one of them. Changed valve cover gaskets and spark plugs. The car is still running bad, and now has a flashing check engine light with no codes coming up. This is a used car I have only had it a couple of weeks.
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Monday, March 19th, 2018 AT 5:43 PM

14 Replies

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

Lets start with the codes that you found originally. Do you know the code numbers?

Roy
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Tuesday, March 20th, 2018 AT 4:59 AM
Tiny
PENNY4146
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  • 8 POSTS
P0301 and the code for crankshaft and/or camshaft sensor (do not remember the number). Since the camshaft was recently replaced we replaced the crankshaft sensor. Replaced valve cover gasket, spark plugs and have checked the coil. Now we are wondering if the computer has to be reset by a dealer after changing the crankshaft sensor. If not maybe the fuel injectors are sticking. Cranked it this afternoon and drove it a bit just to see if any codes would pop up. The check engine light came on and stayed on and is now pulling a p0304 you can smell gas and it is running bad.
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Tuesday, March 20th, 2018 AT 5:49 PM
Tiny
ASEMASTER6371
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Okay. How did you check the coils?

You now have two misfire codes. I would inspect the coil boots and look for any white marks on the boot. It would indicate electrical leaking and not getting to the plugs.

Roy
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Wednesday, March 21st, 2018 AT 3:44 AM
Tiny
PENNY4146
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  • 8 POSTS
By pulling them off one at a time while the car was running. There is no white residue on the boots. They are black.
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Wednesday, March 21st, 2018 AT 4:15 AM
Tiny
ASEMASTER6371
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Okay, when you pulled them off while running, did you see any spark?

Roy
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Wednesday, March 21st, 2018 AT 4:33 AM
Tiny
PENNY4146
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Yes and the engine ran worse.
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Wednesday, March 21st, 2018 AT 4:50 AM
Tiny
ASEMASTER6371
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Okay, then they were working.

The next step is to look for any vacuum leaks. Make sure all the hoses are connected, not damaged and connected.

Beyond that, it could be dirty injectors not spraying correct patterns. Fuel additives rarely work. The correct way to clean them is to disable the fuel pump and use a kit that injects the cleaner directly into the fuel rail and run the engine. It cleans the injectors directly.

Roy
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Wednesday, March 21st, 2018 AT 4:55 AM
Tiny
PENNY4146
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So you are saying this has nothing to do with the crankshaft sensor being replaced? It does not need to be synced to the PCM by the dealership?
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Wednesday, March 21st, 2018 AT 5:23 AM
Tiny
ASEMASTER6371
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There is a crank sensor relearn procedure but it will not cause your misfire codes.

Do you still have the crank sensor code?

It does not need to go to the dealer any shop with a scan tool and perform this function. It takes about ten minutes to perform.

Roy
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Wednesday, March 21st, 2018 AT 5:25 AM
Tiny
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The original codes were p0014, p0017 and p0300.
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Wednesday, March 21st, 2018 AT 6:53 AM
Tiny
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The only code now is p0304.
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Wednesday, March 21st, 2018 AT 6:54 AM
Tiny
ASEMASTER6371
  • MECHANIC
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Okay, that is a misfire code for cylinder four.

Could be:
Spark plug.
Coil.
Injector.
Vacuum leak.
Low compression.

Roy
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Wednesday, March 21st, 2018 AT 6:58 AM
Tiny
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I will check those. Thanks.
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Wednesday, March 21st, 2018 AT 7:36 AM
Tiny
ASEMASTER6371
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You are welcome, keep us updated.

Roy
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Wednesday, March 21st, 2018 AT 10:01 AM

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