My mondeo has just failed its mot on emissions. What determines/ retifys this?

 

crystal ball time

petrol/diesel?

What aspect of emissions, post the readings up.

 

Petrol

fast idle HC: 318PPM FAIL

second fast idle
CO: 0.34% FAIL
HC: 409PPM FAIL

 

What year and engine size

does it use oil?

is it running ok? any misfiring etc.

when was it last serviced

any fault codes?

 

1.8 duratec 51 reg
Uses a bit of oil
No misfires
Due a service
No fault codes

 

Not much to go on:
CO: 0.34% FAIL - possible catalyst deteriorating OR mixture too rich
HC: 409PPM FAIL - HIGH, maybe leaking injector or compression loss?
Or old spark plugs, maybe fouled by the oil usage?

Do you have the other readings from the test? Like CO2, O2 and lambda-number?
What are the readings at idle? (Also include CO2, O2 and lambda-number if available).

 

 

Data is not enough to get an exact conclusion.
Start with the service that is due.
Then retest and proceed with further tests if necessary.

 

Im an MOT tester myself here is some pointers i posted on another site

High HC reading means excessive unburnt fuel could be cause by:

1. Spark plugs need replacing or faulty leads,cap,rotor arm,coil pack check ignition system
2. Faulty CTS ( cold temp sensor )
3 Mechanical fault if present engine will not be running even
4. Lambda sensor
5. Defective air filter

High Lambda reading means the AFR ratio is not correct could be caused by:

1. The engine having a high HC level see above to rectify
2. A leak in the exhaust system even if a minor leak
3. A defective lambda sensor
4. A leak on a vac or intake pipe.

High CO reading can be cause by:

1. All of the above
2. Was the vehicle tested at correct temp was cat allowed to get to operating temp
3. Defective Cat