FAILED EMISSIONS | Technical matters | Back Room Forum

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Wed 11 Sep 2002 08:00

FAILED EMISSIONS - KRISS

I have a 93 Audi 80 2.0 E which has just failed its MOT on the emissions test. The fast Idle results were as follows: Fast Idle CO vol % should be between 0.00 and 0.30 actual reading was 9.98, Fast Idle HC vol ppm should be between 0 and 200 actual reading was 706, Lambda should be 1.030 and 0.970 actual reading was 0.712. The car is fine starting from cold and will run ok for as long as I want it to but if I stop the engine and go back to it in say half an hour it runs like a pig coughing and spluttering and it takes all my time to just keep it running. This lasts for about 5mins and then it seems to right itself. I have taken it to a Bosch specialist who plugged it into the computer for a couple of hours and said it might be an internal fuel leak he also said that the ECU would let him go so far in to its programme and then kick him out. Anyone out there with any suggestions I would be very grateful

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Wed 11 Sep 2002 10:42

FAILED EMISSIONS - John S

KRISS

The figures you quote indicate this car is running excessively rich on fuel, hence the high CO and HC, both of which indicate inefficient combustion. It also explains why it starts well from cold - the mixture is too rich.

Lambda indicates the deviation from stochiometric conbustion - ie a lambda of 1 indicates the correct ratio of air to fuel to just give complete combustion. The fact it's so far out confirms the fact that air/fuel ratio is way out.

Unfortunately there are a huge range of possible problems from the simple (blocked air filter) to the complicated (faulty sensors or ECU). You need Andrew Moorey or his Tune-Up colleagues to look at this, as it's difficult to diagnose at a distance.

Regards

John S

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Wed 11 Sep 2002 17:26

FAILED EMISSIONS - Andrew Moorey (Tune-Up)

As you say John difficult to diagnose without seeing it. Could be failed Lambda sensor, dribbling injector(s). Trouble is you could throw a lot of money at this without solving the problem without the correct equipment and troubleshooting routines. Look in Yellow pages under car engine tuning and conversion for our nearest operator.

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