My nightmare

[JVZL1]

My son came over with his 2008 Aveo with the CEL on. Codes P0137, P0301, and P2270. The car was running very ruff I could hardly get up my ramps. I do not know how long these code have been up. So I checked for leaks and bad connections. Found none replaced both O2 sensors. The downstream pulled the threads out of the pipe. Luckily a thread chaser worked. Being the car was running so bad I did a tune up, plugs, air cleaner, oil and filter. I cleared the code started the car it died, took a few tries to even run. It is running very rough still and you can smell the rich fuel going through.
So I have unplugged the negative side of the battery and will try to morrow. I would appreciate any thoughts or suggestions I’m old school still learning this TEC stuff.
Thanks For any input you may have
JV

[avguy]

Sounds like it runs worse now after the work you did - is that correct? Was there any oil in the plug wells?

One quick and easy thing to try is removing the upstream O2 sensor and briefly starting it up to see how it runs without it. If it improves quite a bit, then the problem is likely O2 sensor-related, or a plugged cat. If no improvement, then post back for additional diagnosis.

[JVZL1]

With the sensor out it still no improvement. Like I posted I do not know exactly how long he has been driving it this way. If it has been pouring fuel through the exhaust for who knows how long. Would the cat would be bad? I also cleaned the MASS Air sensor with MASS cleaner.
No oil all clean.

avguy thanks for the reply.

[JVZL1]

So when I fired it up still smell raw fuel would this be the cat plugged and not getting the air needed for the O2 sensor. It will start and run ruff and die. I can feather the throttle to get some RPMs and then dies.

[avguy]

With the sensor out it still no improvement. ...

You did remove (unthread) the upstream O2 sensor from the exhaust manifold, correct? If so, and there was no change in performance, then the primary problem is not likely to be a plugged cat.

[JVZL1]

Yes I took the sensor out. It ran the same maybe a little longer before it died.

[rwags]

Just thinking it sounds like the engine isn't getting the correct amount of fuel, as in too much...if it smells rich . Could it be a misfire? or a bad coil that feeds the spark plugs? It also might be a bad fuel injector putting to much fuel into cylinder causing the fuel not to burn all the way before it's exhausted?

[avguy]

Do you have (or can you borrow) a compression tester? IMO it would be good at this point to eliminate a mechanical engine problem before getting into all of the other possibilities. Very fast and easy to do on these vehicles.

[JVZL1]

The most frustrating it’s not throwing any codes. This is beyond me. I’m not one to throw part and hope for a bulls-eye. So I’m having it towed to shop.

Things I will look for before it goes is a vacuum leak and pull the plugs to see if they are fouled or wet.
Avguy I appreciate the advice you have given.

I will post back what they find.
JV

[avguy]

The most frustrating it’s not throwing any codes. ...

It may be that the misfire counter hasn't been able to get high enough to exceed the limit and trip the code. The fact that it had a misfire code previously, along with the way it's running, would make one suspect there's a big misfire that just hasn't had a chance to be flagged yet.

One other easy thing you can try, assuming you have someone available to crank, is to ground the plugs to the block and see what the spark looks like. A spark tester would be the normal way to do this, but I'm assuming you don't have one of those tools. If you do this, pull the fuel pump relay first prevent more gas from going into the cat.