PO300 on 2003 silverado 5.3L vortec. Replaced fuel pump, ...

Hello, my name is \*\*\*\*\* \*\*\*\*\* to Just Answer! I will be assisting you with your questions today. Give me one moment while I review this.

I’m very sorry that you’re having this issue and together, we will get this figured out. I will need your help too because I can’t see, touch, hear or smell anything that’s going on with your vehicle. We may also require some specialized testing tools in order to assist us in diagnosing the problems due to the complexity of today’s vehicles. JA will offer a phone call to you at an additional fee, it’s your choice. Please be patient with my replies, I reply back in question order received. If I send you an attachment, I will tell you, BUT, you will NOT get it on a phone; you must be on a tablet or PC. Please let me know when you are satisfied with my answers too so we can close out your question. Please do a static and running compression test. Please check for a plugged [exhaust](/topics-exhaust-chevy/). Thanks again and all the best:) Ron Please feel free to text me back if you need any more help. Thanks again and be well:) Ron

I don't know what a static test is but I am running around 150 to 155 on the compression test on all cylinders. The exhaust was brand new summer of 2020.

Cranking only is the static test, now the running test needs to be done. I would also smoke the intake for lower intake vacuum leaks. I would also check freeze frame data and MODE 6 misfire data with a scan tool. Thanks again and be well:) Ron

I don't know but I also did intake gaskets to replace [knock sensors](/topics-knock-sensor-chevy/) as well

Then please show me the scan data I asked for so I can diagnose it. If it all checks good, then something was missed. I still need to see the running compression readings too. Thanks again, Ron