Hi had my s type for around two months. I have so many issues with misfiring bad coils, water ingress and leaking rocker gaskets.
And finally thought it was all over. Three days ago replaced a coil on cylinder 7 which is passenger side uk 1st from last.

Cars been driving really nice except today got a catalyst below efficency threshold bank 1.

Could this be because of the misfiring I had three days ago or could it be the start of another misfire?
I didn't feel any misfiring but sometimes they start unnoticeable by feel or hear and get worse.

Any help appreciated

Darren

 

This could be due to all the misfiring issues you had - but, let's think positive - I would look into changing the O2 sensor post cat converter first - but do realize - misfiring coils pass unburnt fuel to the converters and it esentially burns up the material inside the converter.

Hopefully, that is not the case with yours - otherwise, if it is - then you will need to replace that converter.

Be sure all the water ingress issues are resolved and also, hopefully, you changed the cam covers, spark well gaskets and all other associated gaskets and torqued down all bolts correctly and sequentially.

 

Thanks abonano all gaskets etc replaced by a hah specialist.
They told me these cats are actually quite string and usually sort themselves out even after I burnt fuel has passed through them.

I forgot to add that u have just used a full tank of fuel with injector cleaning additive in it and wondered if done of the dirty deposits ate working there way through the system which perhaps brought the code up?

 

If you have one of the better OBD tools (well, one with better software), you can graph the O2s. On your car type all 4 are the same technology (not true for later cars). The upstreams should switch often from high to low and back. The downstreams should do it rarely. So you'd hope to see a graph of the downs that's leisurely or hardly moves compared to that for the ups. The sides (banks) should be fairly alike.

I'd guess it's not the O2s but that's a way to go about checking.

If they're bad enough you get O2 sensor codes, of course.

 

My obd does do live data. I'll have to look at it.

 

Works better with nice hot cats (well, sensors) so rev it a bit if they're not switching.