Emissions fail and then pass!

[theb]

Hi,

 

Just wanted to write about my recent MOT in case it helps anybody else in the future:

 

First test: the Zed failed on emissions. CO2 reading too high at around 0.6 limit is 0.2 (other two readings were fine). When the car was run at fast idle, the Zed would hold the revs at around 2.5k revs for a minute or so, then shoot up. As such, the reading was pretty duff to say the least.

Garage said "9/10 it's the cats that have gone, you'll need to replace them". I wasn't convinced and went to research....

 

Second test: filled up the tank, put in a fuel cleaner and then took the Zed for a 45 minute run (4th gear, >4k in revs - was really good fun :-D ). Straight to the garage and it....failed again. Garage said the same thing again.

 

 

Third Test: told the garage to chuck it on the diagnostic for an errors, clean the throttle body, spray some EGR down it to clean the MAF sensors too and shove some Cataclean in the fuel tank and take the Zed for a spin to warm the cats before testing. This time....a pass :-)

 

Idle rev thing not solved but I've never noticed it while driving but holding that beast of an engine stationery for a period of time while reving would probably p@ss of the engine.

 

Moral of the story: do the simple stuff first before being persuaded to chuck money elsewhere.

[Tricky-Ricky]

Cats need to be pretty hot before they will work efficiently, which really means a decent spirited run before MOT, otherwise even when held at high engine speeds when stationary they can sometimes be too high to pass.

[monkeybrain1234]

4K rpm, get it up to 6,000 rpm to really clear its lungs. I had the same issue with the Alfa, a good blast few days before MOT always cleared the lungs.