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High HC reading on 1995 VW jetta

Failed emissions test due to high HC and NOx

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6ya6ya
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Posted on Jan 02, 2017

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SOURCE: High HYDROCARBONS on emissions test. I

hi.
first thing to do is change the air filter. even if it appears clean, the airflow can be blocked enough to affect the petrol air ratios in the engine which will give high HC readings.
changing the spark plugs can give a cleaner spark, and better ignition, with lower HCs. high HCs could also be caused by traces of oil getting through worn piston rings and valve stem seals and burning in the combustion chamber. there are many oil additives that can help stop this and reduce HC levels as well.
hope these suggestions help

Posted on Aug 28, 2011

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ercupa190
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SOURCE: 2001 Volkswagen Beetle Failed Emissions

Dear Sir:

EGR Ehaust Gas Recirculation system.the basic component is vacuum-operated control valve that recirculates the exhaut gases through the engine the engine intake manifld and cylinders where they recombine with the incoming air/fuel mixture.The check need special equipment, to some workshop.
sincerely. God bless you.

ernesto cuadra
managua, nicaragua. c.a

see the diagram for details.
3_29_2012_8_23_30_pm.jpg

Posted on Mar 29, 2012

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2 Answers

1995 Honda Civc failed Emmisions test


Emission test by codes reader? or smog? Any codes?

May 22, 2017 | 1998 Honda Civic

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Failing emissions testing due to high NOX (oxides of nitrogen)


I have seen several people posting emissions failures due to high NOX (oxides of nitrogen). Nox is created when the engine's internal combustion temperature gets to high.

Two reasons this can occur is improper coolant levels and a malfunctioning egr system. The egr system injects exhaust gas from the exhaust and uses it to line the cylinder walls.This in turn reduces the combustion chamber size and internal combustion temperatures. Ultimately this reduces the amount of NOX created. These systems functioning properly can be the difference in passing or failing your emissions testing because of high NOX ppm.

on Jun 18, 2010 | Chevrolet 1500 Cars & Trucks

1 Answer

C15001993 truck 4.3 v6 Failed Emissions HIGH CO again


Sounds like you lost O2 Control

Check fuel trim & data with professional
scanner & such

You done as far as working at home, you did all
you can

You have a rich condition (CO)

Seems as though the coolant sensor is not working &
your in open loop

Mar 05, 2013 | Chevrolet C1500 Cars & Trucks

1 Answer

Fail smog test


fist i would like you to post the year make and model of the truck along with the HC ppms and NOX ppm it would be very helpful but high hc and nox can be attributed to a faulty EGR system nox is produced when the combustion chamber temperature gets too high so a small amount of exhaust is cycled back into the air stream to help cool them there are other causes but without looking at the levels its much harder to say

Dec 06, 2012 | Cars & Trucks

1 Answer

1994 cadillac sedan 4.9 engine will not pass smog. Noxious too high.i replaced egr, erg solenoid,changed oil, still nox is high.hc and co pass


The HC is high because the CO is high, CO is caused by to much fuel being delivered. You will want to check the Oxygen sensor and make sure it is functioning properly. You will want to check the fuel pressures, including rest pressure. We have seen leaking injectors cause this problem. You will want to make sure the thermostat is working correctly also.

First thing to do is check over the sensors that control the fuel mixture as it sounds like you're runnign too rich. This could be due to a faulty water temp sensor. If this is the problem then the ECU (Engine Control Unit / aka computer) will be leaving the car constantly 'on choke' and not reducing the fuelling as the engine warms - so unplug the sensor and clean the contacts on both sides with some switch / electrical cleaner (not WD40) and inspect the wiring for any signs of damage to the insulation especially where it runs over other components and through the bulkhead

If the engine is running well and the state of tune and ignition timing is good (15 degrees BTDC) then most likely the converter itself is bad. Usually NOx readings will go down as HC and CO readings go up, and as a result it is extremely rare for a car to fail an emissions test with all three things if the Catalytic Converter is working properly.

A bad oxygen sensor can also cause a failure similar to this, but will usually cause HC/CO readings to be high (but NOx readings would be low), or the opposite - high NOx but low HC/CO readings. The O2 sensor is located in the exhaust manifold just before the bulge of the catylst and at the point where the 4 pipes join together.

Unfortunately there is no good way to test the Cat. Highly specialized equipment is necessary to do this, however a temperature test might clue you in to one that is bad.

After driving the vehicle for several miles, immediately check the temperature of the converter at the very front and the very rear of the unit itself. The rear should be at least 100 degrees (F) hotter than the front. If the two are close to the same temperature then it is proof the converter isn't working very well.

I have to note though that temperature testing is far from conclusive. I've seen converters that pass test with flying colors but still ended up needing to be replaced.

Aftermarket converters tend to be less effective than factory converters because they are not built specifically for your vehicle. Instead, a universal unit is welded into some exhaust pipes so that it will fit. Generally this isn't an issue, but if you live in a 'green' state such as California where emissions standards are very strict, it could pose a problem.

Keep us updated.

Aug 02, 2011 | 1994 Cadillac DeVille

1 Answer

I just failed my emissions test due to "High HC"


The simplest thing you could do is inspect the connectors to the sensors. You can also try cleaning the intake and the sensors using carb cleaners or tuner cleaner. Check also for vacuum hoses that may have gone bad or could be loose.

May 31, 2011 | 1999 Isuzu Rodeo

1 Answer

I just failed my emissions test due to "High HC" and "High NOx readings. HC are a result of unburned fuel in the exhaust and NOx is the result of high combustion temperatures and/or high...


it is the EGR valve that has a large bearing on the emission control so run the fault codes to find if it is the valve or the solenoid control that is faulty

Apr 12, 2017 | 1999 Isuzu Rodeo

1 Answer

Failed smog


means that the hc,co2,nox, emissions are too high, you will need the numbers in ppm on the read out to begin diagnossis

May 08, 2010 | 1995 Oldsmobile Aurora

1 Answer

Failed emissions....high nox


Sticking egr will raise everything except nox. Bad o2 bad cat hard to give an accurate diagnosis with out checking it

Oct 12, 2009 | 1994 Lexus LS 400

2 Answers

Emissions failing with high NOx


Change the lambda/oxygen sensor in the exhaust.

May 21, 2009 | 1994 Mitsubishi Galant

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