Question about 1996 Volkswagen Jetta

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My 1996 Jetta 2.0L failed emissions. The CO was too high. Is there an air/fuel mixture adjustment anywhere? I changed the oil and checked the air filter, but couldn't find any way to adjust the air/fuel mixture.

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  • yadayada
    yadayada Aug 26, 2010

    there is no such adjustment

  • aldo_hoyt Aug 26, 2010

    I suspected there was no adjustment. I dug out my old VAG tester and found out that the #1 O2 sensor was bad.
    Thanks!

  • aldo_hoyt Aug 26, 2010

    I suspected as much.

  • aldo_hoyt Aug 26, 2010

    My OBDII tester reported that the O2 sensor voltage was low, but the VAG tester specifically stated that the O2 sensor was bad.

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First off do you know when the CO was too high? was it at idle or accelerating? The mass air flow sensor adjusted the mixture based off of readings. I would take it all apart and clean everything. Also your front o2 sensor may need to be replaced as well.

1) take the intake hose off of the throttle body, and air mass meter. Clean this completely with carburetor cleaner.
2) remove mass air meter from air filter housing, and clean this also
3) clean throttle body completely with carb cleaner and a soft brush
4) check integrity of the entire PCV system from where it clips onto the box on the front of the engine block, up through the diaphragm on the valve cover and the hose leading to the intake tract. All are likely in need of replacement.
Thank you,
Lee

Posted on Aug 26, 2010

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1 Answer

What does it mean when it says co


CO? That means Carbon Monoxide - it's a rather toxic and poisonous gas emitted from the exhaust system.

When they check emissions on cars CO is one of the gases they measure. If the level is too high .. your car fails the emissions test. I believe in the USA the emissions test is known as the 'smog test'?

If you have a problem with excess CO emissions on a car the cause is often an incorrect fuel/air mixture or a faulty sensor called the lambda/oxygen sensor in the exhaust system

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I failed emissions test. The HC and CO both failed. I was told by a family member that it sounds like the catalytic converter and I wanted to know how much that would cost or estimated cost to replace


Rich fuel mixture is leaking fuel injectors,failed oxygen sensors

Need clean air filter,new spark plugs

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This is a social web site we use as you do so prices are are over the internet less labor of coarse

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1997 nissan shows no sign of problems but wont pass emissions


Hi.

Do a code scanning and make sure that there are no DTC codes stored. Check for common faults that may result in high emission:

Check air intake and air filter, check also the sensors in the air intake (MAF and IAT). A problem in the air intake may result in rich mixture and in high emission.
Check that distribution is OK, replace sparks plugs.
Make sure that oil has been bled and replaced.
Check that there is no vacuum leak. A vacuum leak may result in lean mixture and occasionally cause misfire.
Double check the O2 sensors, they determine the air/fuel ratio in the mixture being injected.
Do an injectors cleanup.
Do a compression test. Your engine is 15 years old. Depending on mileage and on maintenance history the piston rings or head gasket may start giving some troubles.
Check the color of the smoke from exhaust and check the result of the failed emission test. That may help understanding what is wrong with the car.

Regards.

Ginko

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My 91 explorer wont pass emissions, Co levels too high and hc levels. Are high as well


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lean a/f mixture means there is too much air compared to fuel. this needs immediate attention since this might lead to over compression in the combustion chamber, which develops to total internal engine failure.

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