P0301 and p0420 missfire and catalytic converter

[Yipikiaye33]

Hello I have a 1.8 valvmatic avensis 2010 . Recently over the last 3 days I have had these 2 codes come up . First p0420 so I put some cata clean in with the fuel and seemed fine then I today p0301 missfire cylinder 1 . I have tested the o2 sensor and it's switching back and forth rich and lean also the temp of the cat on the scanner but I'm struggling to understand the readings there's 2 cats or sensors on 2 parts of the cat ? PLS see pic below

[Konrad C]

I am not an expert, but I would investigate the misfire first. I would check the spark plugs, coil pack and connections. When was the spark plugs last changed, and are they the proper Denso SC20HR11 Iridium plugs? Swap the coil pack between cylinders to determine if the pack is failing. A misfire could be affecting the emission system! 

The scanner you have is showing what the two lambda sensors are detecting.

If you can't make head or tails of your scanner info, try search on the web. If still stuck ask an auto electrician.   

[Yipikiaye33]

Hi and thanks for your reply yes the coils are denso . I am not sure about the plugs as there very deep in the engine I am going to get a deep socket and get them out . I have noticed my o2 sensor is giving a strange signal on the live data the graph looks very strange . Also noticed the maff sensor reading is very low 1.6 m/s on idle I could be on to something . Where can I find the acceptable values too 

[Yipikiaye33]

O2 sensor on idle

[Yipikiaye33]

I think it was a dirty connection on maff sensor as I got all the dust out the connector and it's now reading 4/grams a second as to 1.6 at idle . Lucky find really . I'll test and let you know the outcome

[Konrad C]

2 hours ago, Yipikiaye33 said:

Hi and thanks for your reply yes the coils are denso . I am not sure about the plugs as there very deep in the engine I am going to get a deep socket and get them out . I have noticed my o2 sensor is giving a strange signal on the live data the graph looks very strange . Also noticed the maff sensor reading is very low 1.6 m/s on idle I could be on to something . Where can I find the acceptable values too 

 

2 hours ago, Yipikiaye33 said:

O2 sensor on idle

 

2 hours ago, Yipikiaye33 said:

I think it was a dirty connection on maff sensor as I got all the dust out the connector and it's now reading 4/grams a second as to 1.6 at idle . Lucky find really . I'll test and let you know the outcome

I didn't think about mentioning the MAF sensor, since you had mention fault codes and O2 sensors.  The MAF plays a part in measuring the air coming in.
I have some diagnostics, but never needed to  use live data.

Well done for finding the fault.

 

[paul9]

You should have a pre-cat and a post-cat sensor, one measures the gas going in, and the post sensor measures what comes out. This lets the ECU adjust the air/fuel mixture and the timing to help the cat work efficiently, and let's the ECU know if there is a problem with the cat. As far as I remember, the pre-cat sensor reading should switch high to low readings fairly rapidly, maybe every second or less, and the post-cat sensor should stay at a fairly steady reading. This is assuming that the car is running properly.