Haynes Automotive Emissions Control | Domestic and Import Vehicles

PREPARING FOR EMISSIONS CERTIFICATION TESTING

Over half of all states now require regular (annual or biannual) emission certification tests. Many also require smog inspections when vehicle ownership changes hands. Obviously, if you've "modified" (tampered with) your vehicle's smog equipment, this periodic ritual of having your vehicle "smogged" can give you an anxiety attack.

And even if you're the type of owner who would never dream of disconnecting a single vacuum line - but you're also the type who neglects scheduled vehicle maintenance, including emission-related components - the prospect of a smog test can be disconcerting.

If you fall into either of these two general groups, you're not alone. Recent statistics from some states indicate that nearly one-third of all vehicles fail to meet emissions standards their first time through.

It doesn't have to be that way. With regular engine maintenance and a straight-forward check of emissions - related components, you can catch nearly all the potential failures which might turn up in a state inspection.

And you might as well get used to it, because state-certified smog testing is going to become stricter and more frequent as time goes on. Specific testing procedures and standards for various emissions levels vary from state to state, but the idea - lowering the HC, CO and Nox levels - is the same everywhere.

So the following information should save you time and money. Time because you won't have to go back several times to pass the test; money because you won't have to shell out extra dollars for the repairs needed to enable your vehicle to pass the test.

Generally, a stock (untampered with) engine will pass the state smog test as long as it's been recently tuned and all the emissions related hardware is intact, hooked up and working properly. If your vehicle hasn't had a tune-up recently, now is the time to do it.

The following items should be checked carefully before a smog test.

1. Make a quick visual check of all emissions control systems to be sure all components are in place and hooked up correctly. If you have reason to suspect a system is not functioning correctly, check it as described in Chapter 3.



2. Inspect all under hood vacuum hoses for cracks, loose connections and disconnected hoses.



3. Inspect all under hood electrical wiring for cracks, torn wires, loose or corroded connections and unplugged connectors.



4. Check the air filter carefully, since a dirty, restricted air filter will cause a rich fuel/air mixture, increasing emissions. Also check the PCV filter, if equipped (see Chapter 3).



5. On carbureted models, check the choke to be sure it's opening all the way when the engine is warmed up (here again, the rich fuel/air mixture caused by a closed choke will increase emissions).



6. Finally, before having vehicle car tested, make sure the engine and exhaust (catalytic converter) system are up to normal temperature (10 to 15 minutes of driving time).

• Introduction
• Troubleshooting
• System Descriptions and Servicing
• EGR System
• EVAP, EEC, ECS Systems
• PCV System
• Air Injection Systems
• Thermac and EFE Systems
• Carburetor Control Systems
• Catalytic Converter
• Engine Management Systems
• Vacuum Diagrams and VECI Labels
• Acronym List and Glossary
• Computer Trouble Codes
• Index