Failing Emissions for CO%... Any help?...

[Mark B]

Hey guys,
I brought my 91 RS Convertable to the inspection station today. It failed for the 2nd time. This time its CO's were at .89% when its not susposed to be any higher than .65% What would cause this to be high? I know the engine has some burnt up oil in it from when my brother owned it.. (When I did the timing chain, it was caked on the block & cover.) Anyway, what other kinds of things would cause me to fail in this test? See my sig for my mods.

Thanks,
Mark Balistreri

[Benm109]

Not sure if this will help, but how old are some of the parts? ex.- spark plugs and wires, O2 sensor, cap and rotor, etc. Have you checked your timing recently? Just some thoughts.

[Mark B]

I did a full tuneup about 1-2 months ago. The only part that you mentioned that I didnt change was the O2 Sensor. Timing is set at 8* advanced. I only run 93+ octance

[Injuneer]

How did the HC look? Generally, running rich will elevate HC and CO, while it reduces NOx. If the HC was also close (but under) the limit, it might indicate running rich. That condition can be caused by a number of problems, including misfires, faulty O2 sensor, exhaust leaks before the O2 sensor, excessive fuel pressure, or faulty cat.

The 3rd Gens have a split bed cat with a "reducing" front end (reduces NOx) and an oxidizing bed in the back end (reduces HC and CO). Air is blown in between the beds to feed the oxidizing section. If the back section of the cat goes bad, or if the AIR pump is not working correctly, you can get high HC and CO,

[Roger in Kensington]

AIR removed?

That'll do it. I'm surprised that they would even inspect your car with the AIR removed.

[Mark B]

Looks like I will just have to buy a sticker.