What do i try next

[vettechjamie]

Hello I recently purchased a 2003 gmc sierra 1500 4.8l  when i bought it it had a p0300 code. i brought it to a garage and they tested the coils and dont think its that.. they think it was fuel injectors.. cylinders 4 and 6 are misfiring according to the shop.. I replaced all 8 injectors and cleared the code.. been driving it for about 10 miles now and now it occ flashes Check engine light and when the scan tool is put to it it still gives p0300.

Where and what should i do next.. current things fixed and changed that ive done to the truck so far.

New Starter

New battery

New evaporator solenoid

New Speed Sensor..

Im at a loss as to what can be causing the flashing p0300 code?

[davester]

how many miles on it?  besides the injectors, and who knows how they tested the coils, all the other changes aren't really relevant.

 

-maybe check/replace park plugs (simple to check, may be due for change).

-check fuel pressure at the fuel rail

 

After that, you can either fire the parts cannon at the truck, or diagnose what's wrong.  And to diagnose, you need to go through the diagnostic procedure for the p0300 code.  google for it online,  it'll list a number of things to check.

 

Personally, I would suggest:

-getting an online subscription to the full service manual for your truck, $50 for 5 years at a site like alldatadiy.com

-getting a good code reader, like a knockoff techii, or autogenuity w gm enhancement, something that can read codes from all the computers in the truck (there's 10+, depending on options), and can also perform a bunch of diagnostic procedures/tests that the full-service manual may ask you to perform