Fiat Cars sold in North America have four basic smog control devices: Air Injection (AIS), Catalytic Converter (OC), Crankcase Breather (PCV), Exhaust Gas Recirculation (EGR).
Tailpipe emissions are usually not the problem when running a Fiat through smog. If your car is properly tuned, and basically running to stock specification then the emissions should come into line with original specs. The problems happen with the functional tests (usually EGR, or Air Injection), and are usually caused by some ill-informed owner, or mechanic removing equipment in an effort to make the car run better. Tampering failures are pretty basic: Put the stuff back, get it working, and try again. I have little sympathy for people that remove their Air Injection pump, plumbing and all (in an effort to regain that 1/2 horsepower they'll never miss) and end up searching the boneyards for all the pieces and parts of the system that they tossed away. This information is designed to help the home mechanic prepare for the inspection, and minimize nasty surprises at the local smog station.
Typical Fiat smog failure is an EGR failure. The EGR system on these cars involves quite a bit of plumbing (be it exhaust routing or vacuum) and this plumbing degrades, or fails over time. Early twin cams had the external (and hard to get, be careful with them) EGR pipes, and the very fragile/expensive EGR valve. Later cars had an EGR port that ran through the head, less pipes, and a more conventional valve.
Some EGR failures are related to a signal problem (ie no vacuum signal to the valve), and some are a Functional problem. (ie when vacuum is applied to the EGR valve, it fails because it fails to make the engine idle rough- this is what the Smog tech is looking for)
Signal problems: This is a failure of the system that sends the vacuum signal to the EGR valve. It can be as simple as a split vacuum hose, but is usually traced to either misrouted hoses or a bad thermovalve. Model specifics are impossible here, but the idea is to consult the vacuum diagram, and service manual. Trace the system bit by bit, and find the loss of vacuum signal. If you find a thermovalve that has stopped doing its thing, check availability. On the 2-liter cars, most valves are still available through Fiat. On early cars with unavailable thermovalves, find a suitable replacement from currently available stock (check parts substitution) and improvise a fitting for that thermovalve. As long as the EGR is receiving a signal when the engine is hot, and the system is not grossly modified, you should pass- The State understands that some mods are necessary when working with older cars. Best of all is to find a local shop that works with Fiat, and find out the latest methods, part numbers etc. that they are using on your specific model. Regulations, and availability change by the minute- it's best to consult a local source if you are having problems getting the system working.
Functional problems: These are usually traced to a bad EGR valve (they plug with carbon and stick, and then the vacuum diaphragm goes bad), or plugged ports. The smog technician does the EGR test by checking for a vacuum signal to the valve, and then by applying vacuum to the valve. If the EGR makes the engine idle rough when vacuum is applied, then it passes. If the exhaust ports to or from the valve are plugged by 15 years of carbon, then it will not do its job. Perform the vacuum test yourself before smogging your car. If it fails, check the valve for plunger movement and smooth operation. If it is bad, replace it- If the valve is good, start checking the pipes and ports in in the system for blockage, and clear them. Many Fiat owners find a good EGR valve, and save it for 'smog time'. When they need a smog, they install the valve that works. When they are driving their car, they remove the valve to save it from the wear and tear that results from regular driving, and install the old, bad one. By doing this, they also save the exhaust ports from carbon- If the EGR valve is stuck closed, it does not plug ports with exhaust... It is a dead end connection! This practice is illegal, but helps many Fiat owners preserve rare, expensive EGR valves.
EGR maintenance consists of clearing the pipes (or port in the head) of carbon whenever they are removed, and keeping your car tuned. Nothing plugs the EGR system quicker than a car with a cylinder miss, or a tired engine. Never plug the EGR ports with something, as it will assure a functional failure- Likewise, if you have a car that has failed due to an EGR functional failure, look for some previous owner's bonehead attempt to disable the system. On 2-liter cars, it is common to find a plate between the intake or exhaust manifold, blocking the port. Many people have done this in an effort to 'improve performance'- It's not viable. Get your EGR system working, get smogged. If you don't like the EGR valve's effect on driveabilty, you could unplug the vacuum hose leading to it... This is again illegal, but also common practice among Fiat owners.
Air injection is pretty basic- The pumps go bad, but are readily available within the aftermarket- Some of the plumbing can be challenging, but only impossible if the original components have been thrown away... As I've stated, I laugh at the stupid buggers that remove the air injection from their cars... I tell them all the same thing: Consult your service manual, underhood emissions decal for proper system operation, installation requirements.
As far as maintenence goes, the only common failures are the check valves. These are GM replacement parts, and should be available for a long time (thank God they used a North American part for a N.A. system). Be careful with the threads/fragile old pipes, and use the replacement item. If you break a pipe, you can always have one fabricated at a local machine shop, using the carcass as a sample. Most of the diverter valves, etc are pretty reliable, and the other electrovalves are usually not tested for function- When it comes to Air Injection, Cosmetic details that adhere to the stock diagram and an operating pump are usually enough to pass your inspection.
Special note re: Maintenence Reminders- Fiat has stated in many manuals that the reminder is no longer necessary- If for some strange reason you get failed on a reminder only, dig up an old service manual (I can get you copies) and fight it. That system is so bizzare, and so unnecessary... I don't want to discuss it if I don't have to. Leave the shell of the non-operating system intact, and forget it.
The Catalyst is the Catalyst- Either it is there, and works, or isn't, and doesn't. If you need a new catalyst look to the aftermarket for a high quality replacement Cat that meets your State standards (CARB in CA), and replace it. The catalyst doesn't really hurt your performance that much- If it works, and doesn't rattle to high heaven, leave it be, and be thankful. (BTW, with talk of roadside State Trooper inspections in the works, Catalyst elimination becomes even scarier)
The Breather (PCV) is even easier- It involves 2-3 rubber hoses (that degrade, get hard and fall apart over time) that are all readily available throught Fiat- Replace them, and forget it. Breather emissions are so smelly, so messy; You and your engine are better off with a tight system.
I hope this information helps- Please leave us feedback if you have specific problems, and need assistance.