3.0 v6 Emissions failure
I've had my GTV for only a few months, didn't realise the MOT had expired & so wasn't able to put it in for a 'pre-test'.
Last year it had an advisory for CO2....needed to be hot & fast idle.
This year it's failed the lot badly, the hydrocarbons being particulary bad. The Tester is a good guy & if he can use fast idle, all electrics on, etc to get a car through, he will, but he says it's 'miles off'. I don't have the figures.
I don't have diagnostics, but a local garage does, so I asked if his equipment could point towards a sensor perhaps, but he says unless the engine warning light is on, it won't show a fault code.
The only advice I got was check the plugs & the air filter. I won't be able to do that until the weekend, but I do have history of bits being replaced. In 2012 it had one or both Cats replaced. Between 2014 & 2015 it had the air filter & plugs replaced. Between 2014 & 2016 it's only done about 7,000 miles.
Just after I got it one of the manifold-downpipe gaskets went. The other was leaking a little. The car was running roughly, - lumpier tickover & very rich exhaust gas, but after the repair it was back running ok, which it still does.
Suggestions as to procedure to suss it out please?