16V failed emissions test (CO)

[ced64k]

I bought a Citroen Saxo VTS 16V a few months ago. The car no longer passed the emissions test. I've already tried 4 times without success.

Year: 2000
Mileage: 149,000 km
L3 engine
Air conditioning
Cylinder head gasket and timing belt replaced at 138,000 km in 2018
The car has not been driven since the end of 2020.
Looks 99% original, no tuning parts

What has been done:

• Original airbox
• New air filter (Bosch)
• New cat (Walkner)
• New spark plugs (Denso)
• New lambda sensor
• New thermostat
• New blue/green/brown temperature sensors (Stark/Stark/EPS)

Already tried: ethanol in the tank

I live in Belgium so I don't have the emission test values, I just know that the CO is too high and lambda ok. The car is currently in a small garage nearby. They discovered that the catalyser has been emptied. They have the measuring device and it was just below the limit but failed on the official test. I hope to receive the complete test. For the time being, they're going to retest it with unleaded 98 petrol instead of ethanol.

We can't drive the car until the test is ok, so we can't try the additives to clean the engine.

While changing the spark plugs, I noticed a bit of oil on the thread.

I saw that some screws on the ECU are missing and I haven't managed to connect to it with Lexia. No engine fault on the dashboard.

I'm running out of ideas

[Manu]

We can't drive the car until the test is ok, so we can't try the additives to clean the engine.[...] they're going to retest it with unleaded 98 petrol instead of ethanol

Tank should have been fully flushed before running again, probably contaminated with foul fuel.


add an injector cleaner on top of a tank of 98, go drive the car on the motorway, do about 20km at 85 km/h in third gear, burn the crap out of whatever is in there, then come back 85 in fifth gear.

Cars that don't run for years are cars that don't run well. Not being allowed to run the engine on a good warm drive does not help.

[VeiRoN]

Originally Posted by ced64k

They discovered that the catalyser has been emptied.

That would be why,fit an actual working cat and it will pass? Or am I missing something?

[ced64k]

Originally Posted by VeiRoN

That would be why,fit an actual working cat and it will pass? Or am I missing something?

Yeah, that's what we thought. The car went through the inspection with a new Walkner cat and a tank full of ethanol, but the CO levels were too high.

The inspector thinks it might be because of the ethanol, so they're going to empty the tank and run it again with regular gasoline. I'm waiting for updates...

[ced64k]

Still no progress, the garage can't find a solution.

I wonder if this Magneti Marelli 1AP.41 ECU could have a problem? Is it possible that a car seems to be running normally but because of a faulty ECU the emission test is wrong ?

[nuttysaxo]

I had an issue similar to yours on my old vtr failed emissions the garage who ran it in for the mot took it back a second time but this time ran forte fuel system cleaner through it ran the car to it was warmed up and then it passed ..

[MartinObviously]

If the lambda readings are good (0.970-1.030)

and CO is still too high, the problem is the catalytic converter. Sounds to me like it's not hot enough when they are testing the car either that or you have a very slight misfire.

What was the CO% measured after fitting the new cat?

Ethanol won't be the problem, ethanol fuels affect the lambda readings though - but you've already said they're okay.

[ced64k]

Originally Posted by MartinObviously

What was the CO% measured after fitting the new cat?

CO2 12.7%
CO 0.5%
O2 2.1%
NOx 98ppm
HC 153ppm
(idle)

[MartinObviously]

Originally Posted by ced64k

CO2 12.7%
CO 0.5%
O2 2.1%
NOx 98ppm
HC 153ppm
(idle)

Ahh yes being a Euro 3 the natural idle has to be 0.3% CO or less.

It's as if the cat isn't working at that value. My decatted 16v managed 0.5-0.6% at idle! With an aftermarket 200cel cat I welded in the CO emissions became <0.1% at idle.

Maybe the cat just isn't hot enough or good enough quality?