2000 silverado p0300

[carlos duron]

I have. A 2000 silverado  5.3 it has a p0300  i replaced downstream o2 sensors spark plugs and wires oil change. When  i start it in the morning black soot comes out the exhuast leaving some sort if black liquid smells like gas    Any ideas on how to fix it   Also the headers arent that hot even at  operating temp 

[sefiroxx]

You'll need a better code reader to determine which cylinders are misfiring. If one or two, then injectors may be stuck open. If an whole side, then chase common items like wiring.

[carlos duron]

I have just simple code reader throws p0300 idk what it has but it throws black fluid at start up what do you think is problem

[davester]

Where does it throw black fluid?

[carlos duron]

On 2/14/2020 at 4:04 AM, davester said:

Where does it throw black fluid?

 I have carven muffler dump straight to the ground on starts ups it throws some kind of soot black fluid my whole driveway is covered in it now i tested 02 sensors seems good also check coil packs also came good idk what to do besides taking it to a mechanic to find out with the scan code

[davester]

have you recently modified/changed the exhaust in some way?

[carlos duron]

11 minutes ago, davester said:

have you recently modified/changed the exhaust in some way?

Its cammed 216/220 stage 3 cam it had rebuilt heads new gaskets  new lifters new pushrods  no cats carven dump it has tbss intake with a fuel pressure regulator   It has new spark plugs and wires coil pack check good 02 sensors check good just did oil change and. New oil filter new fuel filter only thing left to change is the crankshaft position  or just take it to a mechanic who can charge me to take a look at it with the fancy scanner

[sefiroxx]

If you upgrade the came, you'll need an ecu tune to adapt. Hopefully your mechanic can do, especially on a dynometer.