Smog test fail

I would google vehicle exhaust gases & do some studying

Given it is a 1992-- 22 year old vehicle & don't know how old
the motor is !

159 is HC & a lot of unburnt fuel

NO may be an egr issue along with overheating

Best study the gases & what is required to address them

You could go with the spark plugs,wires,synthetic oil, new air filter,
check out the egr system,pcv system & vacuum leaks,thermostat,
oxygen sensor,clean maf sensor

I'm NOT saying throw parts at it,I'm saying check it out & do some
testing, to find some problems

You have to take out a lot of fuel & bring down your misfire counts,
engine temp etc

I would guess after your best efforts ,you need to replace the
exhaust converter,I would, unless it is only 5 years old or newer

wow, no context but i can read your mind?
ok SMOG failed. right?
what speed, there are 2 in uSA, 15 and 25.mph.
so there are 3 tests, which one. all are PPM in usa.
parts per million.
but is that HC , CO, or NOX? or ?

based on your numbers is HC
hydrocarbons or in barstool, its raw gasoline leaving rear of car.
unburned fuel..

572 ppm is way too high 12-19 is normal
id say the CAT is bad.
but can be , engine is bad, and burned out the cat.
that is why all savvy mechanics, check the that the engines
holds closed loop status, (EFI closed loop) at the speed yours failed.
if not in closed loop the cat will burn up (rich)
that is first.
Once that is cured. you check HC again. if out of spec
you did burn up the can , new cat time.

that is the correct way.

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

Any codes? any problem tune up, catalytic convener, burning oil.

Jose, I don't know if this will give you the answer you are looking for because there are many things to consider here. The exhaust gas recirculation valve (EGR) is one of the main things involved in reducing NO emissions. This valve is controled by the power control module. (PCM) This is your vehicles computer. The PCM monitors the vehicles speed and will command the EGR to open when the vehicle attains a certain speed, which is why the ASM test being done is recorded at two different speeds. At 25 MPH your vehicle failed the hydrocarbon (HC) emissions limit and this could be for a number of reasons. When is the last time you car was tuned up? Old spark plugs, wires, clogged air filters, oxygen sensors, leaking injectors (personal experience) or the PCV valve could be contributing to the results of the test. I guess that the easiest way to go is to tune up the engine replacing the spark plugs, wires, air filter and the PCV valve and don't forget to have the oil changed at the same time. Only then should have the vehicle retested and see what the results are. Should it fail again you may have to consider having the EGR or the catalytic converter replaced depending on what portion of the test fails. If the NO fails I would consider the EGR. If the HC fails then I would consider the catalytic converter. Good luck with this.

High HC means moisture in the system. Try driving it longer then take it to the smog shop. Otherwise it could be hard like a head gasket or easy such as a PCV not functioning. Any ways you should always drive it about 20 miles before smog check, longer when the weather is cold.

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

change your O2 sensor.

You did not post the odometer reading on the van but base on the year it should has over 85,000+ miles on it.

The most likely source of the high Hydrocarbon (HC) is clogged or drippy injectors.

Change the fuel filter if it is over 48K miles.

Ran two or more tanks full of Chevron gas will help clean out the fuel system.

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The air fuel ratio can be off is the air filter is clogged or the mass air flow sensor give incorrect data to the computer (ECU).

Change the air filter is it over 20,000 miles or you can see sunlight though it.

Use CRC Mass Air Flow cleaner or electronic part clean to gently clean the mass air flow sensor.

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Change the oil to 20W50 or one grade higher to prevent blow by.

You current motor oil is soak with HC from blow by.

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Make sure the tires are at 32 psi

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Do the smog test is a COLD morning?

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REMOVE excess cargo off the van.

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These are little things that I would do.

If the HC is still high at 25 mph then you will need a professional fuel injector cleaning or replace the injectors.


Please post more data on the third smog test on the comment window.

Do an oil change with 20W50 oil (or one grade higher) to prevent blow by during the test.

You current oil has HC from blow by though the rings.

Do a fresh oil change will lower the HC.

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Change spark plugs,wires,cap and rotor if they are over 24,000 miles
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Make the smog check appointment for the EARLY MORNING. Colder air will help the fuel burn better.

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Clean or change the air filter and pcv valve.

Clean Mass Air Flow sensor with CRC Mass Air flow cleaner or electronic part cleaner.

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Do a quick wipe down on the wires and cap to take the moisture off.

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Check spark plug wire contacts for corrosion.

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Fill the tank to around 3/4.......just in case your fuel pump is weak.

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Ran the truck for 20+ minutes on highway before the test.

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Do not carry excessive cargo on the truck bed.


These are the little things I would do to get the HC and CO down.


Please post more information on the comment window.