Alfa 156 2.0JTS failed on emissions, idea's?
Hi guys, my 2.0 JTS went in for an MOT last Saturday and failed on the emissions, everything else was spot on, which I was pleased with as I do spent a lot of time and money keeping her tidy, and I do the work myself, but unfortunately the emissions were well off.
I took the car away and during the week I replaced the four spark plugs, drop some engine flush in, did an oil and filter change (none of which were overdue, but wanted to cover all basis) sealed a slight exhaust leak at one of the joints, replaced an ignition coil, reset the ECU, and then dropped a second bottle of Catalclean in the tank (I'd previously put a bottle in before the test) Tonight I took a detour on the route home from work and went on the motorway to get the cat red hot before dropping into the test centre for a re-test...Once again she failed.
I'm not overly savvy with the emission parameters but I could see 2 of the figures go green which I take as being good, but the CO2 on idle needed to be below 0.30, and I saw the readings fluctuate slightly, but never below 0.45, which isn't even close?
The tester said the cars idling rough, which I do agree with, you could see that in the engine judder, and whatever is causing this is resulting in the engine running rich, hence my emission failure.
Has anyone any ideas what could be the cause of this rough idle leading to poor emissions results?
I'm fully away of the lambda connection issues on the JTS and I've previously hard wired these in, I'm also aware about the 2 large connector blocks at the back of the engine. I used to be plagued with MCSF errors, but I seem to have solved all these issues and recently the cars been running great, with no no error messages, just this rough idle and emissions.
Any suggestions welcome, many thanks for taking the time to read,