How To Get Your Modified Muscle Car Through Tough Smog Checks

Editorial Note: The writer is a qualified but not practicing California smog tech.

Getting an old car through a smog check can feel like pulling teeth, getting a modified muscle car through can feel impossible. And its not just California. Known as “Section 177” states, those 13 are: Connecticut, Delaware, Maine, Maryland, Massachusetts, New Jersey, New Mexico, New York, Oregon, Pennsylvania, Rhode Island, Vermont, and Washington.

The first thing to note is that passing smog is essential because it is tied to registration. No smog = no registration sticker = pulled over by the cops all the time. The DMV will let you pay for the registration to avoid fines for late payment, but will not issue stickers for your tag until you pass smog.

There are two distinct ways to beat the smog check: the first is not to modify your car (yeah, right) and the second is to buy vehicles from 1975 and earlier, which are smog exempt. In fact, scanning craigslist, you can see that smog exempt vehicles, especially trucks, are worth more than those which do.

But wait, not modify your car? Isn’t smog about making sure tired, smoky, polluting engines are off the road?

Well, yes, in theory, it is. But nowadays the smog check does not involve using an exhaust probe. That’s right, what is actually coming out of the tailpipe isn’t relevant. Instead, the tech relies on two tools: the OBD1 or 2 port, and his eyes. The OBD port scan plugs into the car’s brain and tells him whether all the emissions systems are working correctly and that it isn’t misfiring, etc. His eyes are looking in the engine bay as the rules state “any tampering” with emissions related systems is a fail. This is really is horrible news for older performance cars.

2001 Bullitt Mustang GT | Photos courtesy of Ford Motor Company

To illustrate, I have a 2001 Bullitt Mustang with 130,000 miles on it. I wish I had not driven it so hard, but it was my first muscle car. It failed smog recently due to a K&N air filter. Apart from this filter, which the car has had for ten years and 65,000 miles, it is bone stock. It had fallen foul of the “no tampering” rule.

Here’s where SEMA comes to the rescue for car enthusiasts: stickers. Many popular aftermarket mods made by members of SEMA have been CARB (California Air Resources Board) approved. They are issued an EO (Executive Order) number, and a sticker with the number embossed is supplied in the box with the part.

Vehicle Emission Control Information label | C.A.R.B. photo

The idea is you stick it under your hood when you fit the part. Kinda weird, this makes a bit more sense when you realize these stickers are like the white sticker installed under the hood of all new cars from the factory to help future smog techs identify and check emissions systems. Now the tech can determine that yes, the engine bay may have been “tampered” with, and have non-factory parts, but it is still smog legal because the components are CARB approved and the EO stickers are present. Perhaps I never put my sticker on, or if I did, my sticker burned up and peeled off somewhere on the road.

Smog techs are good about this: if they spot a non-factory item, they will often point it out before testing and failing you. I suppose they don’t want to take your money and then fail you right away for something so obvious. The tech who rejected my Mustang told me what to do “Call K&N, and they will send you a new sticker.”

Turns out what he meant was go to their website, and fill in this form.

Notice how this process asks you to provide photos of the part on the car and the car’s VIN.

Within the week they had sent me the stickers; the car then passed smog.

The important thing here is not the dumb admin wheelspin, or the ridiculousness of stickers being what makes the car legal (like when you were in 8th Grade collecting stickers) no, what is important here is that by being patient, and understanding the rules, there’s no reason why you can’t modify a car and it still be smog legal.

This is also a great reason to buy parts from established, “name” brands. I bought the K&N filter in 2009, and ten years later they are still with us and have a customer service department to send me the sticker. Had I bought a “Dave’s-Here-Today-And-Gone-Tomorrow” filter, and had “Dave” gone out of business, there would have been no website and no-one to send me a sticker. The only option would have been to replace the part.

To reiterate then, if the car has any aftermarket part related to emissions which do not have CARB approval and an EO sticker the vehicle can’t pass smog. Period. This means there are lots of cars out there which cannot pass smog without retro-fitting factory parts. A sub-$5000 search of Craigslist shows tons of cheap, fast cars, Camaros, Mustangs, Nissan Z cars, which run well but will never pass smog due to non-CARB aftermarket parts or non-smog savvy owners. Fox Mustang sellers often make a point of commenting when the car does have smog.

At this point it is worth remembering the first thing said here – that smog is tied to registration. When you sell a car in California, it is the seller’s legal responsibility to smog it. No ifs or buts. Sellers of these un-smoggable cars often point out how the registration sticker is good for almost all of the following twelve months – they are suggesting that you will hold the pink in their name, avoid paying registration until you must, and only then discover that registration is impossible because it can’t pass smog.

Not so long ago, I tire kicked a ‘95 Camaro. It had been bought out of state as a roller, and the seller had fitted a motor and transmission from a ‘98. The thing would never smog because the systems were different on both cars, and the smog rules say the car must have the emissions systems it had when it was new, not those from a later model.

It is possible to get vehicles like this approved but involves visiting a smog ombudsman, where you need to prove the car has all the systems, working, which the VIN says it should have. The reality is this kind of engine swapped car is likely to be more hassle than it is worth, and it is better to find another example. I offered to pay the full asking price in cash if he got it smogged; the seller wouldn’t even let me drive the car; all he wanted to do was sell it without smog to someone who didn’t know better.

Given how awkward smog is, it is worth reminding ourselves why we have smog laws. Introduced in the early seventies as a way of dealing with urban pollution – children who lived alongside busy highways used to grow up retarded due to lead poisoning from the lead put in gas as an anti-knock additive – today we tend to perceive only the downsides of smog legislation: complicated cars and bureaucratic red-tape to jump through if you’re a car owner, and a minefield of expense and frustration if you’re a collector/hotrodder/hobbyist.

Truth be told, California’s smog laws, while stricter , globally are probably somewhere in the middle in terms of inspection strictness. Singapore, Japan, and Germany are three diverse nations which have far stricter rules than in the US. In England, vehicles must pass an annual inspection, the MOT (Ministry of Transportation) test which covers not just emissions but all features of the car. Any visible rust or damaged lights are a fail. In these countries, you see a few older cars, and fewer still untidy, tired ones.

Smog forms from NOx (nitrogen oxides) HC, ( hydrocarbons – unburned fuel vapor) and sunlight. This is why Los Angeles, being sunny and a valley suffers particularly severely from smog. Over the decades a wide range of devices have been used to defeat smog, focused on making sure there are less NOx and HC in the atmosphere. One example of this is the transition from vented gas caps to a sealed fuel system with a charcoal evaporation canister to contain and recycle the gas vapor. Another was a move away from high compression and high power motors since high compression generates NOx, and high-performance motors like to run rich, meaning plenty of hydrocarbons come out of the tailpipe.

The bottom line here is that while you can jump through the administration hoops, dealing with smog is a huge hassle; all the time my Bullitt Mustang couldn’t pass smog, it sat away from my home, in storage. This meant getting K&N the photos they needed was a pain: I had to make a special trip to the storage unit to take the pictures. Because it was sitting, I disconnected the battery.

To pass emissions, the car has to show the DMV computer in Sacramento that it has run its emission system tests (“monitors”), and they all work correctly. Disconnecting the battery wipes the record of the successful monitors. When the EO sticker arrived, I fired up and drove for an hour to let it warm and to allow these monitors to run. When I took it to be tested, all but one monitor had run, and my car failed smog on that one incomplete monitor.  Frustrating as this was, I had only myself to blame. I have a new OBD2 tool, ( BlueDriver, it’s excellent) and that could have run the test for me, telling me I had one monitor still to run. My point here is that all of this is navigable, but it is so much hassle all of which has nothing to do with actually wrenching on old cars you probably don’t want to bother.

Summing up, the best way to manage smog is to avoid it altogether and buy pre-1975. If your budget or preference is for later stuff, making sure all your parts are EO approved is critical. For anything more extreme, or if you’re keeping the car forever, living or having a PO box in the right county should allow use. The caveat here is that when buying, it must have smog; otherwise, you cannot register it in your name.

About the author

Jon Summers

I’m an Englishman living in California working as an Automotive Historian and Freelance Consultant.
Read My Articles

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