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Master Auto Tech.
Master Auto Tech., A.S.E. Certified Master Technician
Category: Chevy
Satisfied Customers: 417
Experience:  Over 20 years working on imports and domestic cars
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I got the 303 error code on a Silverado 08 5.3 I have

Customer Question

I got the 303 error code on a Silverado 08 5.3
I have replaced the following:
Spark plugs
Spark plug ignition wires
Checked all coils and all are good
Changed fuel pumps twice
Cleaned air mass flow
Still continue to have the code pop up and stability track light
Once you clear the code it runs good until it resets and the check engine light comes on again and it's runs shaky in low rpm.
What else I'm I missing?
Supposedly the dealer told me that I'm looking at a cam problem or something withing that severe of an issue.
Any suggestions?
Submitted: 3 months ago.
Category: Chevy
Expert:  Master Auto Tech. replied 3 months ago.
I'm sorry you are having problems with your vehicle. I will try to help.I'm a full time mechanic and have been a mechanic for over 20 yrs and I work part-time here on JustAnswer to help you and others repair their own vehicles, and I get credited by your ratings.. So before leaving the site make sure and leave me a rating. You can still reply to me as many times as neeed, even after the rating.. I will need for you to be my hands and eyes since I'm not there.So when it sets the code it's going to kill the injector so you don't ruin the cat. That's why it runs worse when it sets the code.
That being said have you done a compression test on that entire bank? And have you tried swapping injector 3 and coil 3 with another cyl to see if the miss follows?I strive to provide 5 star service. If I have satisfactorily answered your question please rate it as such and hit submit. Doing so is the only way I get compensated for my time. Also it doesn't close the discussion so we will still be able to communicate if there are further questions.
Thanks
Sonny
Customer: replied 3 months ago.
Thank you for your response. I forgot to mention that I have done a compression test on all and all are good compression. I did swap coil 3 with another cylinder coil, erased the code and it came back with same code. Swapped again to a different cylinder coil to recheck, erased the code and came back with same code. I know that the coil is good. As a matter of fact I went bought a new coil threw it in cylinder 3 erased the code and still came back with the same code. Let me also add that I have checked for air leaks and have none.
Expert:  Master Auto Tech. replied 3 months ago.
it's possible you have a lifter problem, cam problem or injector problem.
I would swap injectors to rule it out. If it comes back #3 then it's either a lifter or cam. But IF it comes back I'd bet lifter. I've done lots of lifters in this year range.
Customer: replied 3 months ago.
My mechanic keeps telling me that it's the fuel pump. He swears that he's had the same problem multiple times and it ends up being a fuel pump problem. Also, isn't there a liquid I can add to engine that refills lifters?
Expert:  Master Auto Tech. replied 3 months ago.
I doubt that it's the pump. If the pressure is in spec then it's fine. Besides, I've never heard of a pump causing cyl 3 miss fire. Random miss fire yes. But not cyl specific.
And I don't know of any liquid per say. But if there was I wouldn't trust it to work. If it did it would be a temporary fix at best.
Customer: replied 3 months ago.
I will do the swaps and keep you posted. Thank you
Expert:  Master Auto Tech. replied 3 months ago.
Sounds good. Thanks
Expert:  Master Auto Tech. replied 3 months ago.
I strive to provide 5 star service. If I have satisfactorily answered your question please rate it as such and hit submit. Doing so is the only way I get compensated for my time. Also it doesn't close the discussion so we will still be able to communicate if there are further questions.
Thanks
Sonny

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