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1998 Saturn failed smog check

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My 98 Saturn SC2 automatic with 20500k miles. I had to take it to a smog star and they said that it does not pass the HC, says it is emitting 54 when it should be lower. Instead of changing the cats, how can I fix this? The guy said I should check the spark plugs, anything else?

Well what do you expect from a 25 year old car with 20,500,000 miles? 😉

Oops I meant 205k miles

3 Answers
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Well yeah spark plugs air filter but too much hydrocarbons is inefficient combustion so anything like even fuel injectors spraying too much fuel can do that. And of course if you have an engine that burns oil then you're just screwed because it's burning oil and that'll create hydrocarbons in the exhaust. You got to rebuild the whole engine to fix that

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Well a 1998 model is equipped with OBD2, have you checked codes and live data?

I did have a code last week, p0341 CMP Sensor circuit out of range, but I deleted it and it hasn't pop up again.

What about fuel trims?

Sorry had to find my scanner.

At idle, short-term, cold jumps around -17 to -18. As it warms up it jumps in between -23 to -25. It drops to zero when raising the RPMs. Long trim stays in -2.3

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Posted by: @bob101nano2

At idle, short-term, cold jumps around -17 to -18. As it warms up it jumps in between -23 to -25. It drops to zero when raising the RPMs. Long trim stays in -2.3

Of course the engine is running open loop when cold but it should settle down and go closed loop once the O2 sensor warms up. It appears that the computer is subtracting a lot of fuel at idle. What do your spark plugs look like, are they carbon fouled?

Nope. Checked sparkplug 1, 2, and 4 and no carbon, in fact 4 was white. Sparkplug 1 and 2 were covered in oil, but the ignition coils were dry. I think I need a cover gasket.

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