P0420

[Lasio]

Hi everyone,

Hope you're all well and having a good festive season.

I've got an issue on my V6 2011 Camaro that I'm trying to diagnose.

Basically the car is running really rough, can't accelerate without rpms skyrocketing. The car's RPMs are running so high, at 30mph sometimes it runs at 1.7rpm and sometimes 1.2, there's no consistency at all. Can't accelerate quickly as car won't respond and RPMs go really high.

To give a bit of backstory, The car has been parked for a good while now. A while back the car had misfires and started to shake with really strong smell of petrol with CEL on which is when I decided to park it for a while as I have another vehicle. However, miraculously, that hasn't happened anymore (the shakes/petrol smell).

Currently there is very little white smoke coming out of the exhaust which I thought is normal. Spark plugs and coils are all new. Already did a head gasket leak test and it came back negative.

Car seems to idle fine when not moving, idling at 0.7rpm and no violent shakes. However, as stated above, car is practically undrivable due to the acceleration issue.

I have a Topdon 800 scan tool, can someone help me out with trying to diagnose the issue? I'm not based in the US so shipping parts that aren't the fix is just waste of time and money.

Cleared all the fault codes in the car and drove it for about an hour like this until faults came back. The only code coming back is P0420. Also the engine is running extremely hot (past the middle point but not at max)
Thanks

[1JEWLDSSRS]

Well heres's some info for you to check out.

https://www.engine-codes.com/p0420_chevrolet.html

[Lasio]

I'm not sure if it's the catalytic converter that needs to be changed as I reset the codes and it hasn't came back. However the issue of the RPMs persist. Can someone kindly let me know what sort of data I should look for in the scan tool and what parameters it should be? This would help a lot!

[KillboyPowerhead]

Maybe look at the short term and long term fuel trims. Mass airflow too if you can see it. Wonder if the air and fuel are consistent while maintaining a constant speed/cruise control.

[Lasio]

Originally Posted by KillboyPowerhead

Maybe look at the short term and long term fuel trims. Mass airflow too if you can see it. Wonder if the air and fuel are consistent while maintaining a constant speed/cruise control.

Changed injectors and throttle body. Car seems to be way better, now it can actually go up to high speed.

The problem is I feel like it's still revving really high in lower gears, not sure if this is normal but 0-30mph it will go up to 2500rpm

[1JEWLDSSRS]

Originally Posted by Lasio

Changed injectors and throttle body. Car seems to be way better, now it can actually go up to high speed.

The problem is I feel like it's still revving really high in lower gears, not sure if this is normal but 0-30mph it will go up to 2500rpm

If that took care of some of the issues, I would now look into cleaning your MAF sensor, it's pretty easy to do, just make sure you disconnect the battery before hand, so when you plug it back up the ECM will start re learning from the start. Also with the trans shifting higher in that range, not too sure if your V6 is like our stock SS's are, and have two different drive modes, when in drive mode, D,the trans will shift economically, and when in sport mode, or S, the factory has it tuned to shift a bit more "spiritedly".. Just a thought to check.

[KillboyPowerhead]

Maybe I'm misunderstanding the issue, but you said "at 30mph sometimes it runs at 1.7rpm and sometimes 1.2". If cruising/driving at a constant speed, constant throttle, are the RPM's constant? Or changing seemingly randomly? Or only changing seemingly randomly when accelerating? If only when accelerating then I'm guessing the torque converter is slipping, or otherwise an issue with the trans.