Help need please Clio 172 MOT fail. (Emissions)

[dicko78]

Hi all I am after a little help if anyone can assist me I took my Clio to be MOT'd away I have owned the car for a few months now but its not been on the road. So I took it for its mot when the guy testing it put it on the gas analyser the CO and the Hydro carbons are through the roof. I brought the car home plugged it into a Scan tool no faults logged at all so I decided to do a little swapping of parts from my track project so to cut a long story short I have swapped all the below over
Throttle body.
Map sensor.
Crank Position sensor.
Air inlet temp sensor.
I have pulled the plugs out one at a time and cleaned them and refitted them no apparent problem there I am going to pull the cat and lambda probes out and swap them tomorrow to see if that helps.
It appears that the car is over fueling the exhaust gas smells very rich and the MPG is poor.
With the scan tool plugged in the timing appeared to to be constantly wandering significantly even at idle. The engine sounds like its hunting up and down.
Please help if you can thanks
Regards : Mike

 

[Tony Hunter]

Possible front lambda sensor.

It might just need a good blast up the road before the test, I always have to do this to mine before a test, take it in hot.

 

[dicko78]

Thanks I am kind of hoping that it's the Lambda sensor I hate emissions faults I am gonna swap the cat and sensors with the one in my garage hopefully that will sort it. It's come in handy having another car in bits in the garage I need to steal one of the rear shocks as that's also seized up. I will have to get on ordering the new ones for my track project. Thanks for the advice I will give it ago tomorrow.


Regards : Mike

 

[Dan@SJM]

What were the emissions?

 

[dicko78]

They where well out of spec it was so out of spec that the guy doing the mot had to remove the probe from the analyser and blast some compressed air through it to clean the line out the
Fast idle test

CO 6.780%
HC 467ppm
Lambda 0.786

Fast idle Ie Test.
CO 6.768%
HC 637ppm
Lambda 0.788

It appeared to be badly over fuelling running 11 mpg on the clocks and smelling very rich at the exhaust as Tony suggested I am going to look at the Lambda sensor I have some spares off my track project so i am going to fit that in the morning the other thing I noticed is the car idles rough when monitoring it with the scanner at tick over the advance on the timing is all over the place up and down.

 

[Dan@SJM]

Lambda sensor. (Precat)

 

[dicko78]

Thanks for all the advice guys I have replaced the front Lambda probe and the emissions appear to have settled right down going to give it a good thrashing then take it back for its re test there was instantly a noticeable difference when I replaced the Probe the sweet smell of unburnt fuel has almost gone and the idle is now far less lumpy.
Thanks all regards : Mike

 

[Tony Hunter]