I have a 2007 the check engine light came on. Had it checked and it coded PO303 cylinder 3. I changed the coil spark plugs and the fuel injector in cylinder 3. Resest system but it keeps codeing PO303. Don't know what to try next. Anybody have any ideas?

 

spark plug

 

did the plugs

 

here are three possibles

1 spark plug and wires

2. head-gasket compression leak on #3

3. fuel rail/ injector issues

 

I had the same. For me worked replacing the injector. Perform a cylinder compression test.

 

@rthornebigfish, would you mind providing me with your VIN? This would allow me to research recall information on your vehicle.

Michelle, Chevrolet Customer Service

 

I'd recommend a compression test first, but more than likely the injector on that cylinder is bad/defective, its a known failure point.

 

I had that code when I first modded my CGS intake came on several times in the first week only when driveing on the freeway at about 65-70 MPH almost 2 years have not seen it anymore. I didnt do anything it just stopped.

 

I have had this problem for a year now, I went so far as to buy a code scanner and just reset the codes. This lasts until the car idles for a short time by which the traction light comes on then the Check engine light. I have changed the plugs, moved the coils and injectors to other cylinders with no success. Still shows No. 3. The light comes on says Code PO303 misfire # 3 cylinder. Does seem to have a miss at times but have been on long trips still getting good mileage (30) mpg, and performs great. Help,this is ridiculas. The transmission shifts hard the first time the light comes on, feels bad when shifting and putting in gear. Oh I have 135,000 miles on it, only one plug change so far. 06 2.4 LT2, automatic. Any help. Also when this car is cold, it surges for about the first 2 miles on the road. The engine rpm goes up and down about 3-400 rpm until it warms up then OK. Cruise control set at 55mph.

 

My '07 is in the shop again with this problem again. (PO300)
Started showing up at 64,000 mi.
Was diagnosed as misfire in cyl 2. Dealer said #2 plug was fouled and replaced it.
Was fine until 68,000 mi (12/27/2012)
Same problem 4K later. Car is now in florida where I am working with another dealer. Car was still under powertrain warranty when problem started. It's off now. All external tests have been done and confirmed ok.
GM tech support is involved now. They have recommended pulling the head.
Just waiting to hear back from dealer.
I'm praying GM will cover all or part of this, as it started while still under the powertrain warranty.
Will keep you posted.