Bah, failed emissions test on my 2001/51k Octy just now.

It failed on the 2nd fast idle test - CO% vol - limit 0.30 mine was 0.92. The lambda reading though throughout all tests was 0.98 which seems ok. HC was 0. Natural idle was ok with c0% being 0.18.

The guy mentioned first I should clean the sensors? Any thoughts and is this a common issue?

Everything else was ok, HC ppm, the first fast idle test came out at 0.85 instead of 0.92 as above.

Cheers folks.

I would also consider a new MAF.

I don't think you can clean Lambda probes.

So potentially swap the lambdas and the MAF?

Oh, natural idle emissions were fine.

I think I'd try the MAF first and if that doesn't cover it then try the Lambda's.

Lummox or fordfan would be better placed to tell you which one.

If you can get to a VW or Audi dealer I'd say there is a very good chance of them having a MAF on the shelf.

Great thanks, anymore input from others or any other experiences would be most appreciated.

Basics first, it's a little rich, what's the air filter like?, it's not mis-firing at all?

If OK the air mass meter would be my first stop, or I have known on occasion with other makes where loading the engine during the test can have an effect on the emissions. Basically you load it by having the steering on full lock, AC and all the electrical consumers on. This has also helped to maintain a constant fast idle on the 1.6 AVU engine.

A damn good thrash can help sort emissions or so i have heard.

Think of it this way it could be the perfect opportunity to get the sports cat you've always wanted. Maybe even the system to match

A damn good thrash can help sort emissions or so i have heard.

Think of it this way it could be the perfect opportunity to get the sports cat you've always wanted. Maybe even the system to match

I agree, my mk4 golf failed on emissions, put some red-x in it and gave it a thrashing up the road a few times and it passed

Oh its not like it doesnt get a little flooring now and again. Everything seems peachy with the engine, no loss of power, no misfire, just bags of power and torque. Air filter was swapped for a genuine one 5k ago. Its due an oil change though but obv that is ok.

Ill go for a little drive after work.

The only thing I have seen is that the temp gauge can drop ever so slighty below 90 for example after I give the car a little shove after say 10 mins of running.

The fast idle was done at 2,000 and 3,000?

I think the test was done with full beam etc on?

Tried this again, 20 minutes worth of driving (inc a few miles of motorway cruising) and the temp guage finally hit the mid spot...opened the throttle fully in second for around 3-4 seconds and the needle dropped down a few mill from 90 degrees. Is the coolant temp sensor causing the car to overfuel somehow?

I would think it is possible that if the coolant sensor thinks the coolant is colder then yes it might run a little richer.

I think then Ill swap this first, but for the idle test it remained at 90 throughout.

Coolant sensor or even possbily the thermostat is stuck open.

Would that cause the high emissions though although the needle was at 90 through the test?

I wouldnt have thought so, try a MAF and then lambda probe number 1 if your not going to pay for some propper diagnosis and have a stab.

Cheers for the help folks, Lambda 1 was the fault, car passed very easily after this. £95 lighter!

Glad to hear you got it sorted mate.

Did you get it fault code tested and was it shown as a fault?

No faults at all, my mate had a very nice Snap On Solus which he used, nothing there at all.

It may not log a fault but there is more to diagnostic equipment than just fault code checking. If the lambda probe is faulty you can check by looking at the signals given out by the probe and if they are working closed loop.

But hey your sorted thats what matters

Yep, thats what we used on the Snap On

OXYGEN (O2) SENSOR. Used on both carbureted and fuel injected engines since 1981, the oxygen (O2) sensor is the key sensor in the fuel mixture feedback control loop.

Mounted in the exhaust manifold, the O2 sensor monitors the amount of unburned oxygen in the exhaust. On many V6 and V8 engines, there are two such sensors (one for each bank of cylinders).

The O2 sensor generates a voltage signal that is proportional to the amount of unburned oxygen in the exhaust. When the fuel mixture is rich, most of the oxygen is consumed during combustion so there is little unburned oxygen in the exhaust. The difference in oxygen levels between the exhaust inside the manifold and the air outside creates an electrical potential across the sensor’s platinum and zirconium tip. This causes the sensor to generate a voltage signal. The sensor’s output is high (up to 0.9v) when the fuel mixture is rich (low oxygen), and low (down to 0.1v) when the mixture is lean (high oxygen).

The sensor’s output is monitored by the computer and is used to rebalance the fuel mixture for lowest emissions. When the sensor reads "lean" the PCM increases the on-time of the injectors to make the fuel mixture go rich. Conversely, when the sensor reads "rich" the PCM shortens the on-time of the injectors to make the fuel mixture go lean. This causes a rapid back-and-forth switching from rich to lean and back again as the engine is running. These even waves result in an "average" mixture that is almost perfectly balanced for clean combustion. The switching rate is slowest in older feedback carburetors, faster is throttle body injection systems and fastest in multiport sequential fuel injection.

If the O2 sensor’s output is monitored on an oscilloscope, it will produce a zigzagging line that dances back and forth from rich to lean. Take a look at the waveform on the opposite page - that’s what a technician wants to see when he checks the O2 - think of it as a kind of heart monitor for the engine’s air/fuel mixture.

O2 Sensor Strategies: Unheated one- or two-wire O2 sensors on 1976 through early 1990s applications should be replaced every 30,000 to 50,000 miles to assure reliable performance. Heated 3 and 4-wire O2 sensors on mid-1980s through mid-1990s applications should be changed every 60,000 miles. On OBD II equipped vehicles, the recommended replacement interval is 100,000 miles. The O2 sensor’s responsiveness and voltage output can diminish with age and exposure to certain contaminants in the exhaust such as lead, sulfur, silicone (coolant leaks) and phosphorus (oil burning). If the sensor becomes contaminated, it may not respond very quickly to changes in the air/fuel mixture causing a lag in the PCM’s ability to control the air/fuel mixture.

The sensor’s voltage output may decline giving a lower than normal reading. This may cause the PCM to react as if the fuel mixture were leaner than it really is resulting in an overly rich fuel mixture.

How common is this problem? One EPA study found that 70 percent of the vehicles that failed an I/M 240 emissions test needed a new O2 sensor.