2000 suburban P0300 code
 

I'm stumped. I've had this P0300 code issue, accompanied by running rough, for several months now. Some days are worse than others. Sometimes almost no acceleration, other times it's just a little sluggish. It has gotten to the point now where the engine light is almost always flashing. The other consistent code is O2 sensor 1 (both banks). I have replaced the O2 sensors a couple times, the Mass Airflow Sensor, plugs, fuel pressure sensor, and probably a couple others I'm forgetting. I have checked the coils, checked the fuel pressure today (I had convinced myself the fuel pump was almost dead - the car almost didn't start today), I removed the O2 sensors to relieve any back pressure issue, etc and everything checked out. We checked compression on the cylinders and all were consistent and in the expected range. What am I missing? What else is left? I'm open to any suggestions. Thanks - Drew

Today
 

Weird thing today. Started burb no problem, 10 min later misfiring badly, leave the house with engine light flashing and driving horribly, stall twice by the time I get to the church 1/2 mile away), stall again in the church lot, restart again and the light is off and driving great!!! What happened? Drove it about 25 mikes, stop and go and highway, with it running great! The light came back on at the end with codes saying bank 1 and 2 too lean. Any ideas? Computer issues?

How old is the fuel filter?

It is one of the few vodkas components that I have not changed, but the fuel pressure was 51 psi last week. If the pressure was low that was the next item to replace followed by the fuel pump, but pressure was good

I'm not sure where the "vodkas" came from in my response. No vodka involved and the fuel filter has not been changed since fuel pressure was good.

CF Beginner,
I am having a similar problem with my 2000 Chevy Silverado 1500 with the 5.3. Did you find the problem???

Not really. I’m still chasing it. I have been to two mechanics now, including a dealership. Of course the dealership found a bunch of other things to fix (lights, wipers, gaskets, etc) and said two fuel injectors were showing low pressure so they recommended changing those. I took the car and replaced the two injectors and the lghts stayed off - for a day. The light is back on (same code) but the car is running better. I’m not sure where to go next. Other injectors?

Drew1,
Thanks for the reply. Are you continuing to drive your vehicle? Was there a fee for a dealership to look at your car?

Yes, I continue to drive the vehicle. With 230k+ miles on the vehicle I figured I had nothing to lose. Some days it had little pep, but most of the time it wasn’t horrible, just annoying. I paid the dealership $99 for diagnostics, which I thought was fair. My only complaint was that I asked them to focus on the ECU and I don’t believe they even looked at that. “We don’t have a history of problems with the ECUs on these vehicles” was the response I got from the mechanic that looked at the vehicle. I did appreciate that the service coordinator took me to the mechanic to discuss his findings.