Good point. A misfire has extra O2 as the fuel didn't burn properly, so the O2 sensor sees more than there should be, and so the fuel trim is changed to try to cope. (If there was unused fuel there is now going to be more. It's not good for the cats but it's better than destroying the engine due to being lean. Ideally we'd have fuel sensors as well as O2 ones but we don't.)

Any modern petrol (gas) car needs properly working O2 sensors, no air leaks, working MAF ( if any), working coils.plugs/etc, working cat(s) and so on. Think of it being a computerised control system with an engine attached.

Once you include gearbox, ABS, etc change "system" to "network" in the above. Mandated by laws.

 

All valid points. Thank you for the input. Sadly it might be a while before I can get it back to the scanner. He is swamped at both his jobs. I did make that tester to check the coils and I indeed found 2 bad and 1 sketchy. I replaced those and the rough idle mostly went away. Still pig rich while cold starting but runs way better warm. Restricted performance lamp went out and all that remains is the check engine lamp. Will update when I can. Again thank you all for the good feedback.

 

Ok so I was able to get into his shop tonight and these are the logs. There are 2 sets. 1 from before a clear codes and 1after.

First set

First set

First set

First set

Second set after clear codes. All next photos are post clear codes.

 

After a clear you need minimum of 2 warm ups to give things a chance to re-flag.

Before the clear it looks very ill, with what may be very bad upstream O2 sensors. The misfires may be causing serious catalyst damage.