Multiple codes after engine swap

2005 CHEVROLET SILVERADO
250,000 MILES • 4.8L • V8 • 2WD • AUTOMATIC
Avatar
BJHASTING
  • MEMBER
  • 1 POST
I recently had a new engine put into my Silverado. Right after picking it up I started to get a flashing check engine light at highway speeds around 55 to 60 MPH only. It would stop flashing when I slowed down or stopped. The only code I was getting was P0300 for multiple misfires. Eventually the check engine light came on and stayed on now in addition to the P0300 code I am getting the knock sensor code 4 the bank two knock sensor. I checked the resistance of the knock sensors, and both are within spec. The engine is under warranty, but I've already brought it back to the mechanic once and he said it had nothing to do with the new engine. He changed a bunch of other things, charged me another $2,000.00 and didn't fix the problem. So, I decided to fix it myself.
Jun 23, 2022 at 10:29 AM
Advertisement
Avatar
STRAILER
  • Experienced Mechanic
  • 55,273 POSTS
What is the brand of rebuilt engine? You will get knock codes if the engine has a lot of internal noise. Also, how does the engine run? Smoothly with plenty of power? I have seen where the fuel pump can get weak causing low fuel pressure which can give the p0300 codes. Also, I would make sure the throttle bore is clean, this guide can help:

https://www.2carpros.com/articles/throttle-actuator-service

Can you please shoot a quick video with your phone so we can hear the engine run? That would be great. You can upload it here with your response.

Jun 24, 2022 at 3:12 AM
Join 2CarPros for free, one of the most advanced car repair communities on the internet. From first-time drivers to seasoned mechanics, everyone is welcome to reply, share details, and get better answers. You can add a temporary image or video first; uploads are limited to 20 MB.
Ask a Free Question
Repair Safety Notice: This information is for general instructional purposes only. Vehicle repair can be dangerous. Verify all information, follow manufacturer service procedures, use proper tools and safety equipment, and consult a qualified repair shop when needed.