Ford Mondeo v6 failed MOT test!!!!

paul@ · 24 Aug 2006 at 20:34

This is from the MOT paperwork

Exhaust emissions Lambda reading after 2nd idle outside specified limits [7.3.2b]

Exhaust emissions carbon monoxide content after 2nd fast idle excessive [7.3.2b]

We have replaced the lambda sensor and the car has failed the MOT re-test.

Any ideas what could be wrong before we take the car to Ford?

Thanks.

ci_newman · 24 Aug 2006 at 20:37

If you've replaced the lamda sensor, chances are that the CAT is dead... Try and get the ECU onto a code reader to make sure no other sensors are reporting faulty

silversurfer · 24 Aug 2006 at 20:47

On mine the ecu flashes its codes out and you can just look up what its trying to say.

I always get an engine fault light on the dashboard, peel back the carpet for the ecu and its does 17 flashes, speed sensor fault. Iam certain its not a problem so I dont think the MOT guys would give me hassle about it ( I have no abs, etc)

I would bet the cat also, try a spare from the local scrappy. Whats your actual readings?

pinkaardvark · 24 Aug 2006 at 21:19

Mondeo V6 has two lambda sensors, one in each bank. Other problems include genral ignition faults, unmetered air from anywhere including after the cat( mine failed once on dodgy backbox(must have been sucking it back in somehow) or dirty/failed MAF.

Get a diagnostic done on it(the lambda faults aren't that reliable but unmetered air or more specifically "lean on bank 1 or bank 2" will show.)

Also EGR pipe can rot and get holes or egr valve can fail.

CypherPunk · 24 Aug 2006 at 21:30

Without knowing the Lambda values it’s hard to say if the cat is at fault, if the Lambda reading is high and the CO is also high it could be that the cat is failing to oxidise the carbon monoxide to carbon dioxide. If on the other hand the lambda reading is low then your engine could be running rich, meaning that there is not enough oxygen in the exhaust gases to convert enough CO to CO2 to allow your car to pass your test. This could be caused by a number of problems, but depending on how severe the emissions are, your car might just need some encouragement to pass the emissions test.

Lopéz · 24 Aug 2006 at 22:06

My money's on a dirty MAF. When you go back for a retest you should always take it for an Italian tuneup first.

Steve W · 24 Aug 2006 at 22:21

Mondeo V6's will pass an MOT without the main catalyst. There are two more catalysts; one in each manifold which are more than capable of passing the emissions test without the central one. (I know, I've done it.)

paul@ · 25 Aug 2006 at 10:03

silversurfer said:
On mine the ecu flashes its codes out and you can just look up what its trying to say.

I always get an engine fault light on the dashboard, peel back the carpet for the ecu and its does 17 flashes, speed sensor fault. Iam certain its not a problem so I dont think the MOT guys would give me hassle about it ( I have no abs, etc)

I would bet the cat also, try a spare from the local scrappy. Whats your actual readings?

Results

Fast idle test

Engine speed ------
Co level 2.67%
HC level 150 ppm
Lambda 0.93

Second idle test
Engine speed ---------
CO level 3.62%
HC level 142ppm
Lambda 0.90

Natural idle test
Engine speed ---------
CO Level 4.62%

I notice the CO levels are far too high from 0.30 - 0.50 and the lambda is failing by 0.10% either side.

Any more suggestions?

Entai · 25 Aug 2006 at 10:18

IIRC low lambda reading means rich air fuel mix and vice versa, Lambda should be 1 if everything is OK.

Also your HC (hydrocarbons) look to be a tad high so I would start looking at a rich mixture problem maybe blocked air filter or dirty MAF sensor.

Might also be burning oil, maybe a check on the breather system.

theNude · 25 Aug 2006 at 13:12

was the engine nice and warm? take it for a italian tune up.. worked in my mums citroen!

CypherPunk · 25 Aug 2006 at 15:27

Unfortunately it’s going to take more than an Italian tune-up to sort that problem as it’s currently running way out of spec. There’s a few things that could be causing the problem, firstly the coolant temperature sensor, if the ECU believes that the engine is cold it will continue providing a richer mixture than needed and won’t enter what is known as ‘closed circuit’ mode, this is when the ECU monitors the exhaust gases and adjusts the air fuel mixture as needed. If I had to guess I would say the CTS is the likely cause of your trouble.

However a few other problems can cause rich running, a faulty MAP/MAF sensor can cause an engine to run rich, however the chances are it would also affect the ignition timing. Finally an engine that is burning oil can cause all sorts of problems with emissions, however it should be easy to cross this problem off by checking the oil level.

paul@ · 10 Sep 2006 at 22:13

Update

On Friday I took the car to the Ford garage for a full inspection test.

Ford claims to have found a loose cable/connector inside the engine that was causing the exhaust emissions to be abnormal.

Thanks for the help and replies.