My 1993 Saturn SL2 just failed the Smog Check

If I read your post right, you are over on Hc and that is all? Check the air filter, check the injectors. You are either not getting enough air or are getting too much fuel.

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

Hi Larry, I your position I believe I would take the vehicle for a diagnostic scan and then check the read outs. There could be a problem with any one of a number of sensors but I believe you'll end up with all odds pointing at the cat. Regards John

the smog test looks like the engine is miss firing, that could cause the timing to be out of whack also, try a old fashioned tune up, new spark plugs, wires, and filters also replace the PCV valve. any time you see the NO that high suspect a miss fire.

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.

How well does the vehicle run?

Assuming that the engine did pass the EGR function test on the emission test results, and the MIL (Malfunction Indicator Light) or check engine light is not on when the engine is running, and if you are not sure when the last time it was that the engine had a complete tune-up, with distributor cap, ignition rotor, spark plugs, spark plug wires, air and fuel filters, then a complete tune-up would certainly help, and if the engine oil and oil filter have not been changed in a while, then they should also be changed before an emission test because long used engine oil traps carbon and it will show up as higher CO on the emission test because the emission analyzer will be able detect the higher CO from the engine oil through the PCV valve.

However, it would seem from those HC readings that there is a vacuum leak, and carefully inspect all of the vacuum lines for any cracks or damage, (especially the vacuum line to the fuel pressure regulator) because cracks in the vacuum lines seem to like to hide underneath the lines.

The emission label under the hood should have the vacuum line routing diagram printed on it, and the vacuum lines should all be checked to be certain that they are all connected correctly.

Here is the firing order diagram for that vehicle to help assist you tune-up the vehicle.

Things to consider or replace...

If you are getting a Check engine Light let me know, it will make things easier to diagnose.

Catalytic Converter
Oxygen Sensor
EGR Valve

Since your cat was replaced you should be looking at fuel problems...even gas cap seal....check fuel pressure,fuel regulator,and evap system.>canister or purge solinoid,o2 senser...high nox is caused by the cat or fuel problems on these engines...high pressure in the combustion chamber...lean condition>air leak on hoses,or high compression caused by carbon build up ...there is no EGR on this car so don't waste time looking for it...hope this points you to your problem

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.


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