Clio Emissions Problem. Help!!

[davehills]

Hi Guys,

Took the wife's Clio in for an MOT today and it failed on emissions!

Slow idle test was fine..

Fast idle the car failed on CO levels, 0.625 and 0.492 (The pass level is 0.3). HC and Lambda readings were passes, HC readings were well below the limits.

The CO readings on the machine were hopping about all over the place and weren't steady; the temperature gauge reads fairly low even after a long run but I'm told that this is normal for a Clio. Fuel consumption is a smidgen higher than I'd like but this might just be down to the type of car.

Any thoughts? The MOT station said that it needed a new CAT but I'm not convinced. If the CAT had failed wouldn't the HC reading be high too? Would it result in an erratic CO reading?

I have tried two different OBD2 readers but couldn't get either of them to connect!

It's a 1998 MK2, 1.2 petrol Clio.

 

[Kev_md]

Same happened to mine a couple of years back, get it up to temp and sit in second gear for a while with revs just under red line,after that take it back in for re-mot.apparently burns all the sh-t off the lambda sensor.

 

[clioben182]

Temp guage should go half way if not new thermostat required mate. Should cure the mpg and the emissions

 

[davehills]

So it's likely to be the lambda sensor, even though the lambda reading is 'normal'?

What I couldn't fathom is why the CO reading was high/unstable but the other readings were within limits. As the CAT is supposed to get rid of CO and HC I'd assumed that if it was faulty then both CO and HC readings would be high?

 

[davehills]

With regards the temp dial, I would assume that halfway would be normal, but it generally sits at about a quarter. I was told that was normal for a Clio, especially during cold weather...

Having said that I don't know what's "normal" for a Clio!!

 

[Ol’ Tarby]

Should sit at halfway and never move iirc?

 

[davehills]

Should sit at halfway and never move iirc?

That's what I'd have thought. Now, where to get a thermostat on a Sunday...

I'll report back what resolves the issue.

 

[Ol’ Tarby]

That's what I'd have thought. Now, where to get a thermostat on a Sunday...

I'll report back what resolves the issue.

Most motor factors are open on a Sunday mate, and I'm sure they'll all stock one

 

[Tony Hunter]

I would defo start by changing the thermostat, the car thinks that it's cold and is fueling to suit this. GSF are open Sundays.

 

[davehills]

Most motor factors are open on a Sunday mate, and I'm sure they'll all stock one

Heh, not down this way! Found one motor factor open and they don't have the part.

Motorworld don't have it either so off to Halfrauds in a min to see what they have got.

We used to have probably four or five 'useful' places open on a Sunday but not any more unfortunatey.

Edit: Even GSF in Totton are shut, along with Eurocarparts, Mayday, Totton Autofactors, Camberley, Kingstons, Swaythling...etc.

 

[davehills]

Update:

Have replaced the temperature sensor-no change. However, the gauge has been reading higher this afternoon; the weather has been warmer.

If I remove the plug from the temperature sensor the gauge drops to zero but the fan cuts in-is this correct?

If I then plug in the old temperature sensor (Cold) then the engine revs pick up; plug it back into the one on the engine and the revs drop back to normal. To me this suggests that the fuel mixture is being adjusted in accordance with the engine temperature.

As I couldn't get a thermostat I removed the old one and tested it by dunking it into some boiling water. It opens when hot and closes fully when cold. The top radiator hose gets hot after running for a while.

I'm therefore reaching the opinion that this bit of the equation is working OK.

What else could cause a high but unstable CO reading? Would a new CAT solve the problem?

 

[Ol’ Tarby]

Faulty lambda maybe?

 

[davehills]

Faulty lambda maybe?

Any easy way to test? (I can check the heater resistance with a meter) The MOT guys said it wasn't the sensor because the Lambda reading was OK...does this necessarily ring true?

Is it work getting a local garage to connect it to their diagnostic machine? How much should/would such a test cost?

(Unfortunately, my OBD2 readers won't work...I have done some investigation and apparently the early Clio's used some sort of proprietary Renault protocol)

Edit: Can I just say how very helpful you have all been so far, it is much appreciated and I'll buy you all a beer of our paths ever cross.

 

[Ol’ Tarby]

Any easy way to test? (I can check the heater resistance with a meter) The MOT guys said it wasn't the sensor because the Lambda reading was OK...does this necessarily ring true?

Is it work getting a local garage to connect it to their diagnostic machine? How much should/would such a test cost?

(Unfortunately, my OBD2 readers won't work...I have done some investigation and apparently the early Clio's used some sort of proprietary Renault protocol)

Edit: Can I just say how very helpful you have all been so far, it is much appreciated and I'll buy you all a beer of our paths ever cross.

Sorry matey but I'm a bit out of my depth now in regards to testing the lambda etc.

where abouts in the country are you? There will be a specialist on here nearby to you that will be able to help

 

[davehills]

Sorry matey but I'm a bit out of my depth now in regards to testing the lambda etc.

where abouts in the country are you? There will be a specialist on here nearby to you that will be able to help

Just outside Sunny Southampton!

 

[davehills]

Took it to the local garage and connected up his diagnostic computer. All the sensors appear to be functioning correctly and the readings for various things all appeared to be correct.

The old cat was pretty well rusted into place so it may well be the original factory fitted one.

Have fitted a new CAT and will re-submit for the MOT tomorrow. Fingers crossed!

 

[davehills]

Car passed today (Yipee!) with the following figures:

Fast idle:

CO 0.014
HC 30
Lambda 1.003

Natural idle:

CO 0.000

 

[davehills]

Thanks to all who contributed to this thread-much appreciated!

A mention must also go to Mike @ Hopkins Autoworks in Totton who had a device to read the ECU codes and managed to remove the rusty CAT securing nuts!

 

[Ol’ Tarby]

Glad you've sorted it mate

 

[davehills]

Glad you've sorted it mate

Me too!!