So my 03 Hummer has check engine P0300 code shooting up.

I've changed spark plugs, spark plug wires, and ignition coil packs.

Autozone did a check engine for me and they said intake gasket.

anyone experience this and know what I should shoot for?

it is not riding rough or anything. If check engine light wasn’t on I would have no idea there was a problem.

i check the forums and everyone states they are taking it to a shop, but never say what the shop did after lol.

any advice?

 

Here are the more common causes that should be checked:

1. Low Fuel Pressure
2. Vacuum Leak
3. EGR system malfunction if applies to motor.

the coils and wires could be tested or just replaced if not working. plugs for sure should be changed if its been awhile.

 

There are so many causes of the P0300. Take 10 vehicles with a P0300 and there could be 10 different causes.
Diagnose to find the source! It could be as simple as improper battery voltage, or low fuel quality or pressure, and major as internal engine damage.
If more than one cylinder misfires, this will increase or decrease the revolutions per minute (RPM) of the crankshaft. If that increase and/or decrease is more than 2 percent, the Powertrain Control Module will store the P0300 trouble code.
If the percentage of the increase or decrease in revolutions per minute (RPM) is between 2 percent and 10 percent, the Check Engine Light will come on.

 

So far I replaced all coils and wires.

fuel filter

and still check engine light.

no other symptoms.

 

Which spark plugs are you using or hope they are not Bosch Platinums. Beyond that I would recommend finding a ECM drivability performance technician, who can go through ECM readings to see what’s off, mainly they can read each cylinders output.

 

Here is the GM DTC P0300 guide (in case you don't have it) you may find it helpful

 

With ONLY P0300 trouble code and smooth running engine,
CKP Sensor Learn Procedure,
is a common confirmed fix:

 

oceanbrave and Hummerz have provided good info to troubleshoot the DTC

I've repaired a few trucks by performing the Crank Relearn procedure when there was not a noticeable miss.

If any part of the rotating assembly or drive-line is replaced then it is a good practice to perform a Crank Relearn

Neal

 

Although, I have been very successful without manipulation. Cheap fix correction without CKP relearn!

 

I feel your pain! I had a slight misfire that wouldnt throw a code for a month. I had the truck to the shop several times. I had leak, smoke tests and a bunch Maf cleanings, seafoam , plugs etc. I kept telling my mechanic i thought it was the intake gaskets and he wouldnt listen. Aftet i got pissed and told him to do leak test and smoke test again. He soaked my motor which caused the knock sensor bowls to fill with water. Then my truck went from a slight misfire to limp mode. So i replaced the knock sensors and harness. Got steel fel pro gaskets for the intake. It wasnt a bad job. Next time i would definately remove the hood. But misfire gone and so is my mechanic.