Help 2003 GMC Serria 5.3. It's missing, no power, P0300 code

[Presrich]

It started last week with a P0430 code. O2 sensor down stream. I did not make it to the end of the day to go pick up an o2 sencer befor it started missing throwing P0300 and check engine light flashing. It has no power, feels like the brakes are on. If I run it down the road it has no power and is now throwing P0101, P0300!

 

Plugs, wires are good. Fuel psi is 48ish at idle, no vacuum leaks. Running very rough and missing at idle.

I am baffled, I need some help?

[txab]

Check fuel pressure at key on, engine off. Should be 55 - 62 any less and you have your answer. Checked fuel filter?

[Presrich]

pressure is about 48 psi not running ignition on. It's about 53 PSI and idle. Feel filter was changed out about two months ago. I will go get a new fuel filter and try that. Could it possibly be a fuel pump?

[Presrich]

Ok

New pump, new filter no change???

Still missing at idle, when you rev the engine it throws a P0101 and aP0300 and the miss gets predominately worse it actually starts detonating in pinging!

[Dnt]

Sounds suspiciously like the catalytic converter has stopped up. Is this a high mileage truck?

[Presrich]

Yes 310,000

That would make sense being that the first coded through was a P0430

[txab]

Did you check the fuel pressure regulator

[Presrich]

I looked at it. I pulled the vacuum line off and the pressure went up. Line back on and psi went back down

[Presrich]

Check fuel pressure at key on, engine off. Should be 55 - 62 any less and you have your answer. Checked fuel filter?

Ok I only get good psi when running

When the pump cycles on engine not running I have very low psi, if I cycle the key on and off the psi will come up a little.

[rjgti]

do you have access to live datat

[muddkatt]

What brand of fuel pump and filter did you install?

[Podor]

Have you checked in to the MAF code? If it is running super lean due to an incorrect estimated load, it will definitely cause your symptoms. The MAF sensor helps the PCM determine engine load by measuring the amount of airflow in to the engine. Check for air leaks in the tubing from the MAF sensor to the engine. Try cleaning the sensor with specific mass airflow sensor cleaner. See if it runs any different with the sensor unplugged.

[Presrich]

do you have access to live datat

No, is that a OBD2 reader?

[Presrich]

Have you checked in to the MAF code? If it is running super lean due to an incorrect estimated load, it will definitely cause your symptoms. The MAF sensor helps the PCM determine engine load by measuring the amount of airflow in to the engine. Check for air leaks in the tubing from the MAF sensor to the engine. Try cleaning the sensor with specific mass airflow sensor cleaner. See if it runs any different with the sensor unplugged.

Yes, so I replaced the MAF sencer. It stopped throwing P0101 Code. It is still missing at idle, no power, when I rev it up P0306, P0300 codes. So I switched spark plugs 4 and 6. I move wires 4 and 6 no change, I moved coil packs from cylinder six to cylinder four no change. I did a compression check on cylinder 160psi.

Back unless I am just totally off track, I believe it's either feel injectors or a plugged catalytic converter????