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Emmisions test help

Just had my car in for an MOT (Alfa 146 2.0 TS) and it failed on the Exhaust emissions test with the following

Exhaust emissions carbon monoxide content after 2nd fast idle excessive (Co 4.67 fast idle) (Co 6.38 idle)

As I understand it, this is way over the target. Additional info is that the car feels very sluggish and that it's drinking petrol. Before the test it had new oil/filter, plugs/leads and air filter.

My first thoughts are either the lambda or the cat, although I've long suspected I've got problems with either the MAF, ICV or possibly the timing.

Any help/suggestions welcome.

Mike

Reply to
MikeL
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Waaay too rich for an O2 sensor problem alone.

Look at the CTS (and possibly the ATS) first, then a sensible signal from the MAF.

If the MIL is not lit, then i'm surprised it isnt as you say performance is impaired.

Tim..

Reply to
Tim..

Many thanks Tim.

The MIL isn't lit. I've tried two different CTS. Performace and consumption were uneffected.

Any idea what ballpark a sensible signal from the MAF would be in?

The cat seems to have a slight rattle. Do you think a broken/clogged cat could result in such high Co readings?

Reply to
MikeL

The readings are way too high for only the CAT to be at fault. Modern engines would emit CO emissions approx 0.5% to 1.5% - far lower than your failure figures. The CAT would bring the emissions down that little bit more. Usually down to between 0% & 0.3%

Reply to
NT

consumption

Nope. You have a fairly serious fuelling fault, caused by an erroneous sensor, but not that wildly out that the ECU has flagged it.

Its impossible to give 'correct' outputs for the MAF, they're all different, but only an output within a particular window will work.

I assume you have checked CTS output at the ecu multiplug or using the live data stream? Just because you've replaced the CTS, it doesnt mean the right figure is being seen by the ECU.

Tim..

Reply to
Tim..

Thanks again of both of your inputs.

I just swapped the CTS for a new one. Unfortuantly, I don't have the equipment to plug into the ECU. It's also had a new thermostat and the engine is getting up to temperature. I think I'm getting out of my depth a bit here, but if we assume the CTS is funtioning correctly and the engine is runnning at the correct temp, would it still be possible for the ECU to misinterpret that, other than the ECU being duff?

Additionally, I unplugged both the MAF and the ATS for the drive home to see if it made any difference. Both performance and fuel consumption seemed to improve.

MikeL

Reply to
MikeL

It's running very rich. First thing I'd check is the ECU coolant sensor and wiring - assuming as you say the airfilter etc is clear.

Reply to
Dave Plowman (News)

Just to update the thread, I changed the lambda and the AFM, went back for the test and managed to scrape through with less than 10 seconds left of the

3 minute second test. Phew...
Reply to
MikeL

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