Running rough and misfire code

BFELCH129

MEMBER
2005 CHEVROLET SILVERADO
5.3L
V8
4WD
AUTOMATIC
240,000 MILES

I bought the truck three years ago. I replaced the alternator and battery two years ago. Water pump and coolant flush last spring. Now it is running rough and I have a misfire code. So far I have replaced the plugs wires.

Friday, December 21st, 2018 AT 1:51 PM

5 Replies

ASEMASTER6371

MECHANIC
52,797 POSTS

Good afternoon,

What is the exact code?

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

Have you checked the compression?

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

Roy

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Friday, December 21st, 2018 AT 2:22 PM

BFELCH129

MEMBER
3 POSTS

Hello Roy,

I am using The snap-on ETHOS scan tool and it displayed P0300. When I checked misfire data it showed Bank 1 cylinder 1, 3, 5 and 7 all with misfires. The passenger side plugs were white, the driver side were black carbon fouled. I'm a little confused as I thought Chevrolet V-8 engines cylinder number one is passenger side front cylinder.

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Saturday, December 22nd, 2018 AT 9:07 AM

ASEMASTER6371

MECHANIC
52,797 POSTS

Number one on all GM engines is drivers side.

Do or did you check the fuel pressure?

Did you replace the plugs?

Roy

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Saturday, December 22nd, 2018 AT 9:13 AM

BFELCH129

MEMBER
3 POSTS

Yes, I have replaced the plugs and wires.
The fuel pressure is:
Ignition on engine off is like 32psi.
Ignition on engine running is 60psi.

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Wednesday, December 26th, 2018 AT 3:01 PM

ASEMASTER6371

MECHANIC
52,797 POSTS

Okay,

What is the compression?

The next step is injectors. need to be sure they are working and being commanded on.

https://www.2carpros.com/articles/how-to-test-a-fuel-injector

I would have them professionally cleaned. the additives have no effect on cleaning at all.

Roy

P0300
Descriptor
Probable Causes
Crankcase Ventilation System for Vacuum Leaks
Exhaust System Has Restrictions
Fuel Injector
Fuel for Contamination
Ignition Coil
Powertrain Control Module (PCM) Grounds Corrosion
Spark Plug
Throttle Body and Intake Manifold Vacuum Leaks
Vacuum Hoses and Seals Improper Connections
Vacuum Hoses and Seals Restrictions
Vacuum Hoses and Seals Splits