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MG MGF Technical - Help, My MGF Failed the emission check.

I’ve just been to the Swedish centre for automobile-inspection and unbelievable my MGF-1,8i (-97) failed the emission check, both the CO and the HC level was way out of the chart (CO=5,1%, HC=310). Has anybody experienced the same problem?
Mikael Fällström


These readings seem terribly high compared to those made on my VVC last July:

CO: 0.0%
CO2: 15.3%
measured at 850RPM


3 thoughts:

1. Was the engine warm (they have a required oil temperature in the UK) when they did the measurements?

2. Do you have any sensor faults logged (though that will involve a trip to the dealer's testbook for reading)?

3. Is the air filter clean - but that's unlikely to cause such a "bad" failure, I would have though...?


My june97 VVC failed this summer, showing 2.54percent CO (hydrocarbons OK at 94ppm) at 2922 rpm (it was OK at 873 rpm)

The lambda sensor was changed, and it then passed, with 0.12percent CO and 38ppm HC at 2734 rpm.

What was the lambda reading ? (should be very close to 1.000)



Thank you for your reply. Here are some answers to your questions:

1.The engine had reached normal working temperature, the inspector even took it for a spin to make sure.
2.I haven
Mikael Fällström


Thank you for your reply.

The lambda reading was 0.88. Could it still be the lambda sensor and how much did you pay for it?

Mikael Fällström

Hi Mikael

I did call it the lambda sensor - but it appears in the Rover books as a heated oxygen sensor. This was replaced, under warranty, along with the exhaust manifold - I don't have any price for this work.

The lambda reading is way off (mine was 0.925, and 1.00 after the sensor was replaced). It's possible that the sensor is not being heated (by a small electric element within the sensor), or the signal does not reach the ECU.

Has the car been tested with Rover's testbook to see if there are any logged faults ?

Good Luck

Your dealers Test Book should pick up the fault immediately

When mine failed it was due to the wires into the lamba/oxygen sensor becoming frayed after rubbing against a nearby heat shield.
The wires run through a heat insulation 'sock' but that had worn thru too.

I remade the connection and rerouted cable and all was well.

If you fancy a go you'll need to remove engine inspection cover, then its quite easy.

If its the lambda sensor itself thats gone then replacement is best left to a garage in my view - due to need to have cunning open ended but ring spanner.

Good luck, John
John Thomas

My VVC (P1LKY) failed its MOT (Its first one) with high emmisions. The CO was 9 percent at 3000rpm. The pass figure was 0.3 percent. As I have been out of the country for seven months the garage initially thought that it was lack of use that was causing a cat problem. The car has only done 18000miles in three years!!
A good run up the motorway failed to solve the problem, the wires to the lambda sensor were checked, all was OK. A full Testbook healthcheck was carried out with all readings absolutely perfect.
In the end we "fooled" the car into thinking we had fitted a new ECU and "Reset adaptives" on the Testbook. This resets the "intelligent ECU" settings to factory defaults and allows the ECU to re-learn the characteristics of your engine.
RESULT:- MOT pass straight away and fuel consumption on a motorway run increased from 30 mpg to 37mpg!!!!!

I reckon the ECU has never been right and a rough guess at wasted fuel useage by running "rich" has cost me 400 pounds. Worth having an annual emmissions check done before the MOT methinks!!!!
Mark Pilkington

This weekend I checked the wire to the lambda sensor and all other connections and wires that I imagine could influence the emission, I found no damage cables or lose connections.

This morning I went back to the centre for automobile-inspection and made another emission check with the following result: CO = 0,0, CO2 = 0,0, HC = 23, Lambda = 1,00.

This time it was unbelievable good. Perhaps I touched some cable or something but with this huge difference in emission! I’m confused, but the car passed and is running wary well.

Thanks everybody fore you help.

Mikael Fällström

I recall once that something like 80% of all returned electronic units from cars that had been replaced under warranty did not show a fault, just dirty connections!

Roger Parker

This thread was discussed between 14/09/2000 and 18/09/2000

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