This morning I took the car for the government road worthy test and it failed due to high CO emissions .

The CO value measured at the tail pipe was 6,2% it need to be under 4,5% (not sure what the units are something they call CO/K value)

If members have any advice on how to reduce the CO it would be appreciated, I have to fix it by the 9th of August otherwise I cant drive the car

The engine is a 2l with 20556 PC´s and running D Jet

Thanks in advance

Start with the basics. Ignition timing, vacuum leaks, visual inspection etc... High CO is a result of rich running condition. (too much fuel / not enough air). Could be caused by a few things, some of which may require diagnostic equipment. (DVOM, gas analyzer, Air fuel ratio sensor) May be something simple like clogged air filter, or 1-2 clicks on the control unit. After inspecting the basics, I would start with the DVOM and test cyl head temp sensor, TP sensor and fuel pressure. These are easy places to begin with. I'm sure you will get some good advice here.

If all else fails, turn down the fuel pressure several PSI, will lean out the mixture for the test. Easy to do.

Get one of these, or the newer version - I check and adjust idle mix before the road worthiness test, you see the impact of any changes you make right way.

your not so far off so change @ ecu or pressure should do it


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As has been mentioned, could be slightly rich, or at least reflective of not burning a all the gas properly though it is also worth noting I have had similar emissions failures just from having older gas in the tank when running the test.

What RPM was the test run at?


I would
1. Make sure you have a fresh tank of gas and your air filter is clean
2. Make sure your engine is as warm as you can get it before testing (if the head temp sensor isnt fully hot it will richen your mixture during the test)

If its still failing by that small ammount:
3. a. If the CO reading is failing at idle, dial the idle mixture knob to the left until 1 click before you start getting a lean idle hunt
b. if the CO reading is failing at speed, dial the fuel pressure down a bit.

There is a possibility you could have an issue with your MPS, but i would start with the above.

6.2 is outrageous should be 2 % Immediately check the manifold air pressure sensor to see if it holds vacuum. If not that is the problem. Colorado less dense air at the higher elevations automatically means a richer air to fuel mixture

do you have a factory manual?
good for step by step check.
you need access to an exhaust gas analyser.

tips about car being fully warmed up at at operating temp before test good advice.

good luck, bright side is emission test picked up car running rich.


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