50-State-Legal Walker Jeep Catalytic Converter Swap

    Failed emissions test? Here are the legal requirements for do-it-yourself smog repairs

    Tom MorrAuthor

    Jeepers who have to pass emissions tests usually know that exhaust modifications downstream of the catalytic converter are allowable as long as the vehicle stays within acceptable sound levels. Tailpipe fumes should obviously be routed away from the passenger compartment, but muffler locations and pipe-routing generally aren't subject to emissions constraints.

    When the catalytic converter is involved, though, regulations can intervene. California is the testbed for emissions ordinances; the rest of the country sometimes follows California's lead. With this in mind, we sorted through California's current catalytic-converter replacement regulations for the DIY Jeeper.

    As of 2009, the California Air Resources Board (CARB) requires all replacement catalytic converters to carry an Executive Order (EO) number, marked in an obvious location on the shell using characters at least a half-inch tall. As part of California emissions testing, technicians must visually verify that a catalytic converter is present and "appears to be properly installed." If a "tampered condition" such as a missing, modified, or disconnected converter is observed, the technician must fail the vehicle.

    For pre-1996 (OBD-I) emissions-regulated vehicles, any properly installed cat with an EO number complies with California's visual inspection requirement. On OBD-II vehicles (1996-current), cats must be application-specific: the emissions technician must verify that the converter is a match for the vehicle by either referencing part numbers in the manufacturer's catalog or by searching the BAR website's listings. Also, vehicles brought into California from out of state must comply with California emissions in order to be licensed there.

    The California-compliant cat-quest led us to Walker, an OEM supplier. (Although Walker cats are original equipment on many vehicles, BAR considers any replacement unit to be "aftermarket," regardless of brand.) Walker's "CalCat" direct-fit application is California-compliant. On OBD-I vehicles, any replacement cat that has a California EO number is allowable.

    In pre-1996 OBD-I vehicles, a failed emissions test can give clues on the faulty components. Here, excessive nitrogen oxides (NO) hint at a hardware problem.

    For vehicles that aren't subject to "50-state" (California) regulations, Walker offers its standard and Ultra converters. Walker's website also lists parts stores and repair shops that sell and install its products.

    The advantage of direct-replacement cats over universal models is that they include OE hangers, heatshields, and inlet/outlet pipe configurations as required. Walker's CalCat line is warranted for 5 years/50,000 miles. Since the company is also a Tier 1 supplier of complete exhaust systems, the company is a source for intermediate and tailpipes plus mufflers and hardware should exhaust leaks and/or other issues require additional parts. The job is sometimes bolt-on in a perfect world, but hardware is often rust-welded in place — removal can involve a combination of penetrating lubricants, saws, cutters, and torches. Also, some Jeepers opt to weld slip-fit joints to squelch potential exhaust leaks.

    Walker is an OEM supplier, so it has an extensive line of replacement parts. For California Bureau of Automotive Repair purposes, every replacement catalytic converter is considered aftermarket and subject to the state's certification process. If the Jeep's existing exhaust follows the stock routing, Walker offers all the direct replacement components and hardware for many popular applications.

    Tailpipe Telltales

    "Check Engine" diagnostic codes are a reliable way to identify faulty emissions components. Tailpipe "sniff" results can also distill clues based on elevated levels of certain gasses:

    HC: unburned fuel - dirty air filter, weak ignition spark, defective O2 sensor, bad fuel.
    CO: dirty air filter, faulty sensor(s): O2, MAP, TPS, ECT.
    NO: exhaust leak; defective O2 sensor, catalytic converter, and/or EGR valve; clogged cooling passages; carbon deposits in heads; ignition timing off; lean air-fuel mixture.

    California spot-checks emissions technicians, holding them responsible for correct catalytic converter installation and functionality, regardless of who did the work. The state requires that the Executive Order (EO) number be at least a half-inch tall and visible on the cat's shell with the part installed to expedite verification.

    49-State Catalytic Converters

    For Jeepers who are subject to emissions testing but not California's strict requirements (currently also adopted by New York and Maine), converter replacement is more straightforward. Aftermarket manufacturers list acceptable replacement converters by engine size. For engine swaps, the converter is matched to the chassis year if the replacement engine is older than the vehicle. Conversely, the converter is matched to the replacement engine if it is newer than the vehicle's model year. The Vehicle Emission Control Information (VECI) label in the engine compartment states whether the vehicle was originally built for EPA (49-state) or California (50-state) compliance.

    This XJ still had its stock exhaust when the cat went bad, evidenced by a failed emissions test and rocks-in-a-coffee-can sound when shaken. Luckily, it unbolted with help from penetrating lubricant applied liberally to the hardware the previous day.
    Projects often snowball: The muffler was rotten, so a direct-replacement Walker unit was also installed. The existing tailpipe was retained here; opting for a new pipe could theoretically make this a DIY bolt-on job.
    This XJ was originally a 49-state vehicle, imported into California. The slip joint allows the new cat and muffler to equal the factory length.
    Ideally, the replacement components bolted in. On this job, the new muffler was welded to the existing tailpipe to ensure that exhaust would exit behind the vehicle and not leak up into the cabin.
    The Vehicle Emission Control Information (VECI) label in the engine bay will reveal if it rolled off the assembly line with California emissions. This XJ has EPA (49-state) emissions; otherwise, the sticker would state "EPA and state of California." A failed California smog test meant upgrading it to a 50-state catalytic converter in order to license it in the state.
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