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Gary, ASE Certified Technician
Category: Chevy
Satisfied Customers: 678
Experience:  Senior Technician
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2008 6.0 silverado is fouling the plug in cylinder 1 only,

Customer Question

2008 6.0 silverado is fouling the plug in cylinder 1 only
JA: Tell me a bit more about what's going on so he can help you best.
Customer: driving the other day and cel came on aslo sevice satbilitrack and traction control and running very rough
JA: Are you hoping to fix this yourself?
Customer: i was hoping but not sure
JA: Is there anything else the Chevy Mechanic should be aware of about your Chevy?
Customer: the voltage is running past 14 and it never does that?
JA: I'm sending you to a secure page on JustAnswer so you can place the $5 fully refundable deposit now. While you're filling out that form, I'll tell the Chevy Mechanic about your situation and connect you two.
Submitted: 7 months ago.
Category: Chevy
Expert:  Gary replied 7 months ago.

Hi there,

All the warning lights are on because of the misfire.

Does your engine have AFM, where it goes from 8 cyl to 4 cyl while cruising?

Cylinder 1 is an AFM cylinder. Could be a rotated valve lifter, then the valve doesn't operate.

What other testing have you done?


Customer: replied 7 months ago.
I replaced plug coil pack also listened to injectors with stethoscope they all sounded the same. Moves the plug wires around to see if it would misfire on a different cylinder. Nothing helped it's the same.
Expert:  Gary replied 7 months ago.

Ok, it is not the spark plug.

Not the coil, (hopefully the coil is firing).

Not the injector, there is injector pulse at the cylinder 1 injector plug?

You say you can hear all the injectors with a stethoscope.

To me you have everything you need, except are the valves operating.

Now take the rocker cover off, reassemble everything else to allow the engine to run with the cover over.

Start the engine and verify both valves operate on cylinder 1, they may look normal while cranking, let the engine start and run to see if both are still operating.


Customer: replied 7 months ago.
OK I had the cover off to make sure springs were in tact. Didn't think about starting it up. What should I look for while it's running and is it going to cover everything in oil?
Expert:  Gary replied 7 months ago.

Ok, I have a visual first like you have done.

I then get somebody else to start the engine for me.

Watch the valves for the cylinder 1.

If one stops operating after a few seconds that is the issue.

At idle speed, a little bit of oil sprays, but is to be expected.

You only need to run until the misfire occurs, if a valve isn't operating at this time, this is the problem.


Expert:  Gary replied 6 months ago.

Hi again,

How did you go with the test I have asked you to do as above?

Do you need any further assistance?

I hope my advice has been of some help to you.


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