Emissions.. trying to find a needle in a haystack

Hi
I have been going through all the post i could find, but nothing helps  
I have 2003 MG TF 135 and cannot pass MOT due to emissions, CO to be precise. I have replaced almost eveyrhing I could, but it still doesn't pass.

On my last try i got these results (translation - measure | low revs| limit | revs > 2000 | limit):
  


I have started with the value being 0.8 or so, but cannot get it past the threshold.

I have currently changed:
Spark plugs - new
Air filter - new
fuel filter - new
O2 sensors new, both
CAT - new (not to the genuine one nap cak10426)
injectors - used but correct for the model (there were blue injectors before, but after a lot of googling i saw that i should have black ones since mine is nonvvc)
Air flow sensor - new

Took 30km drive before the test with 4000+rpm and engine was around 100 C when testing.


The strange thing is that on low revs the value is 0.4 and on high revs it jums to 0.6. Did anyone experiance something similar to this?
I have access to OBD scanner (generic, not pscan) but it doesnt give me much info apart from if i check noncontinuos monitors, there is an issue with Manufacturer defined - Monitor ID MID $06 and $02.
And if I choose Emissions Test in the app, CAT and Oxygen always say NOT PASSED.

Any help or ideas would be appreciated, since i'm starting to lose my hope. 
I have the second exhaust controller disconnected, because it would not open right pipe even when Revs are high. 

Hi there,
failing on emissions is usually an MGF problem rather than a MGTF one since the TF has upstream and down stream O2 sensors.

But there are 2 possibilities
1. the cat is not genuine-this can make a difference, a used genuine one is a better choice.

2. this problem came up recently in the MG Owners mag --Charcoal canister faulty due to failed internal switch . This will fail an MOT on emissions

The switches aren't avialble separately but the whole canister is -the only way to obtain the switch part is to get a secondhanded canister.



Mike

Thanks for some ideas. Do you know if it is possible to check if the switch is working? Checking voltage or something like that?

Also, another question, maybe related, after digging some more, I noticed that my intake manifold is from vvc. But some pictures had it shown with nonvvc. Could ir be that these one were put into non vvc as well? Or this will be previous owners attempt to upgrade it to vvc.
I have checked and I don't have the vvc brain that sits on the side between the manifold and the engine

You have a VvC manifold and VVC injectors. Has somebody fitted different camshafts, as well? These engines will run with the cam timing incorrectly set and that can be checked without spending any money.

I'm not sure about camshafts, didn't dig into the engine itself. By any chance you have some instructions on how to check them? Would I need to remove the top part of the engine or can it be checked through spark plug hole for example?

This isn't the place to explain checking the camshaft timing but if you search for Rover K series camshaft timing, you will soon come up with some useful information. Measuring cam lift is a very different matter and probably beyond the scope of what you are trying to do for now. I have heard that there can be problems when both exhausts are open due to excess oxygen being sucked in but I am not competely certain of the details.

I have taken the car to mechanic to check the camshafts and he said everything was fine there was an issue with temp sensor. I thought finally, it will pass.

But unfortunately it didn't help

However I noticed a new thing. When I plug my OBD2 reader and check post cat O2 sensor voltage, it remains almost static around 0.85v however if I rev it to redline couple of times and then keep 5k rpm for some seconds the value start fluctuating between 0.2v and 0.8v. the strangest thing is that when it start fluctuating and I shut the engine off and start it back up the value goes back to static 0.85v, but when it fluctuates and I keep the car running it just keep going up and down without becoming static.

Anyone know what this could mean?

Yes, it means that you have no idea what is going on. That sounds unfriendly but plugging in a diagnostic tool without having the diagnostic skills to interpret the results will lead you up the garden path. I' ll ask you. What should these signals look like? What is the correct voltage swing? Are these sensible results, and if not, what is the data telling you?

Five minutes of googling suggests to me from the data traces that your mixture is rich at initial idle, leaner after revving the engine and your cat is suspect because the post cat and pre cat should not be tracking . Go and read up on post cat sensors.

The cheaper replacement catalytic converters are problematic due to a minimum of reactive material.
I had an annual battle with emissions until I bought an oem cat. After it sailed through everytime.

I am inclined to agree. From my sketchy understanding of the system but 50 years of looking at scope traces, I think the cat is becoming saturated and simply stops working. If the cat were working, the pre and post cat signals would be very different. They aren't.