CO emmission problems

[edwards]

My Golf 1.4cl failed the MOT due to the CO emissions what could be the problem?

[KebabMeister]

CO stands for Carbon Monoxide.  It is a by-product of burning fossil fuels.  You don't say what year your Golf is and whether it has a catalytic converter?  Is it fuel injected?  It would depend on whether it's fuel injected or carburetted on where I would check first.  Here are some things you can do yourself (if you're good at DIY).

Check your air filter.  If it's too dirty you're engine is starving of air and will make your fuel richer and increase your CO.

Check your spark plugs.  Too wide a gap, or dirty plugs, will give a poor spark and will not burn the mixture as efficiently as it should do.  If mixture not burning properly you'll have unburnt fuel going through your exhaust causing higher CO.

Vacuum pipe off airfilter/inlet manifold etc.  Can effect running of engine and ECU will compensate altering CO level.

Blocked breather pipe/breather cap.  Can affect CO readings.

Faulty oxygen sensor (if catalyst fitted) giving incorrect signals, or default signal, to ECU.  Can cause higher CO.

If you car has a carburetor then it may need tuning and the air/fuel mixture adjusting.  This will need to be done by a garage.  It's usually better done after new air filter/spark plugs fitted.

If car is fuel injected, could be fault with Engine management system, or Engine Control Unit (ECU) giving wrong inputs to engine.  Will most likely need garage tuning.

Think that's the main things!

So, what year is your car?  Is it fuel injected?  Is it serviced regularly?

[KebabMeister]

Oh, another.  If your engine is really high mileage then it maybe burning oil which will cause a higher CO reading.  This could be expensive depending whether it's piston rings or head gasket etc.  It's not uncommon with older high mileage VWs.

[edwards]

Thanx KebabMeister for replying, its an L reg, 1994. Its in the garage at the mo, mechanic think its the lambda if not the cat, not cheap but thats life!

[KebabMeister]

Yeah, the lambda is the Oxygen sensor that I mentioned.  It basically measures the amount of oxygen passing through the exhaust and is situated as close to the engine as possible.  It tells the engine management system how much oxygen content the exhaust gases have and then compensates so that the engine 'air to fuel ratio' is maintained at the most efficient 14.7 parts air to 1 part fuel (14.7:1).  Obviously if it isn't working then it's either supplying the wrong data or the engine management system automatically switches to default mode which is okay, but not 100% accurate!

Hope it passes soon!

[KebabMeister]

BTW if your car is in a VW garage then try and get them to fit a non-genuine oxygen sensor.  You can fit 'universal' type make ones at sometimes 1/3 the price.

[BillyNoMates]

Excellent advice from kebabmeister. If it's an 'L' plate vehicle, the Lambda sensor will be well outside it's useful life by now. As said - don't buy the manufacturers replacement, get an equally suitable replacement - there are plenty to chose from.

[edwards]

Thanx guys, the good news is it wasn't the lambda after all, two of the spark plug leads were knackered and the car wasn't sparking up as it should be. Also something to do with a build-up in the exhaust system. I got to say you definately know your motors!! Thanx again and who knows you may be offering your sound advice again!!

[jimmy654]

What year is it? could be a carburetor
http://www.10w40.com/individual/carburetor-rep air.asp