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Discussion Starter #1
Hi guys,

I have a 1.4 litre Peugeot 207 (2007 1360cc)

I had it taken for an MOT recently and it failed pretty badly on the emissions test. Which are found below:

Fast idle:
CO = 7.83% (Max = 0.3%)
HC = 279 ppm (Max = 200ppm)
Lambda = 0.78 (Max = 0.97-1.03)

Second Fast idle:
CO = 8.81% (Max = 0.3%)
HC = 270 ppm (Max = 200ppm)
Lambda = 0.76 (Max = 0.97-1.03)

Natural Idle
CO = 5.9% (Max = 0.5%)

So initially, the lambda sensor readings seem to just stay quite low and not oscillate like they should so I bought and replaced that with a new NTK sensor.
After resetting the ECU with the scan tool and taken it for a drive, the values are all still the same and the O2 sensor is still not oscillating.

I plugged it into a fairly cheap scan tool to get this data (Creader 3001). If there's any extra data that I can provide which could be useful, do let me know.

As all of the emissions values are way off it doesn't seem likely to me to be a catalytic converter issue entirely.
I don't know the last time the car was serviced. I bought it used a year ago and it passed the MOT just fine, including the emissions test last year.

Has anybody seen this before/ know of a solution to it? Any help would be much appreciated.

Thanks very much

David
 

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if its the normal narrow band sensor fitted then on live data it should oscilate between 0.1v and 0.9v if its stuck around .8v or higher and not moving then its telling you your running rich. if possible check short term and long term fuel trims. combined trims should be under +/- 10%. again if the system is rich you will proberly have high minus fuel trims as the ecu is trying to take fuel away.
Also check Sensor 2 on the exhaust after the cat. When hot it should be stable around 0.8v If it reads the same as the front o2 sensor then it indicates the cat is bad and not working
 

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Discussion Starter #3
if its the normal narrow band sensor fitted then on live data it should oscilate between 0.1v and 0.9v if its stuck around .8v or higher and not moving then its telling you your running rich. if possible check short term and long term fuel trims. combined trims should be under +/- 10%. again if the system is rich you will proberly have high minus fuel trims as the ecu is trying to take fuel away.
Also check Sensor 2 on the exhaust after the cat. When hot it should be stable around 0.8v If it reads the same as the front o2 sensor then it indicates the cat is bad and not working
Hi,

Thanks for the response.
After swapping to a closed loop, at idle, the pre-cat sensor reads about 0.25V and will not oscillate at all. It will decrease to about 0.18V with a bit of warming so it does seem to indicate that something isn't working there.

Short term trims after heating read +25 and long term has stayed at about +0.5 thus far.

The sensor after the cat slowly climbs at the car gets warmer and warmer and sits at about 0.85V after a short drive - I think that one seems to be working fine with no fluctuations at all.

Also, does the fuel injection system require the post-cat sensor to actually run or is everything controlled by the pre-cat sensor?
 
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