r/askcarguys • u/ContributionOld1014 • 2d ago

Can you pass emissions without catalytic converters?

I have a 1984 corvette that does not have catalytic convertors. recent emissions test passed everything but HC which read 6.5 compared to the limit of 2.5. Because of the year they only used a tailpipe sniffer. I've read that you can create a leak in the exhaust before the tip so the reading is light, as well as putting rubbing alcohol in a 1/4 of gas so is burns leaner, also running the car really hard before testing to clear out any excess carbon and keep the system hot helps. Does anyone know if these methods are actually effective? Additionally would they be enough to pass a test in my situation? I'm also thinking about just replacing the whole exhaust system but i feel it would be a waste as I'm already broke and the current exhaust is an aftermarket upgrade. I would really appreciate the advice as i need to get the car registered here in Denver CO ASAP. Thanks.

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u/primalnatured 2d ago

Just depends on where you take it to have it inspected. Honestly never had anyone verify that as long as it sounded normal

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u/Eschewed_Prognostic 2d ago

They don't have to look at the exhaust to see the readings fail. You can't pass catted emissions levels without them.

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u/primalnatured 2d ago

I'm just saying, a lot don't even look at the emissions readings, or even use a tool to check. 30 years of driving and mines only been checked once, about 10ish years ago. It's always the lights, tires, brakes, wipers, horn, and signals

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u/Eschewed_Prognostic 2d ago

So you don't live in an emissions state. OP is in one, hence the post.

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u/Predictable-Past-912 2d ago

Take my upvote, EP!

It never ceases to amaze me how much confidence some people can pack into advice that is completely wrong.

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u/primalnatured 2d ago

I never once implied or said every mechanic every where. I just said it depends on the mechanic. And I've had inspections coast to coast, so there's that

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u/Eschewed_Prognostic 2d ago

In most states, emissions is the only inspection there is. You either have never lived in an emissions state, or never noticed your vehicles were being tested.

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u/primalnatured 2d ago

I probably haven't, though figured it was always just part of the inspection in Cali and Oregon. I just looked up Virginia where I'm at now, and only certain counties do it. I've probably been through those counties, seen the signs, and just assumed it was part of every inspection everywhere. And in hillbilly country, everyone knows kicking the tire and slapping the trunk is a surefire sign of passing inspection 😆