Since my 78 Bronco is now in Tennessee I was asking around about emissions testing. I originally assumed that my bronco would be exempt from testing due to the fact that it has no emissions equipment which is how it came from the factory. I checked the TN DMV website which stated that only 1974 or prior vehicles are exempted from testing. How can this be? Anyone have info on this?

 

Your '78 did not come from the factory without emissions equipment unless it was originally sold outside the US. Even then, it probably had some stuff.

Your link does not open.

This site says '75 and newer:

The Official State of Tennessee's Department of Environment and Conservation, State Parks Website

It appears your visual is a cat and a gas cap, although I can't imagine the actual test doesn't test those as well.

http://www.state.tn.us/environment/a...le/facts.shtml

Why do you think your vehicle had no emissions equipment when, by '78, everthing in your weight/vehicle class had cats**, evap, pcv, egr on most, carbs with closed vents, low compression, roundish cams, retarded cam timing, idle screw limiters, fuel filler restrictors etc etc etc???

**Post 3, maybe not on the cats--

 

I know that the 78 bronco is a non catalyst vehicle. Cats were added in 79. It has a sticker on the valve cover stating non-catalyst truck. So how in the world can the truck pass emissions with no cat?

 

Emissions testing applies to passenger cars from 1974 up and light trucks from 1975 up. Only a handful of states have dropped the visual and atmospheric inspections that are necessary for most vehicles prior to the 1996 model year. I know here in Missouri there are no longer any emissions inspections for vehicles manufactured for the 1995 model year and earlier. However, many states still require at least a visual "equipment presence" inspection.

1996 marked the advent of the Federally mandated OBD-II emissions system which can be accurately checked by simply connecting a diagnostic link to a stand-alone computer. Testing on earlier model year vehicles would require much more (and more expensive) equipment to test so the testing was dropped by some states with the idea that as vehicles older than 1996 aged, there would be fewer of them and the testing/equipment would be more expensive than feasible for such a small number of vehicles.

Positive Crankcase Ventilation (PCV) was present on passenger cars as early as 1967-68 which represents some of the earliest application of so-called "emissions" equipment.

 

I guess my question is how in the world can my bronco pass emissions if it came from the factory with no cat?
They only had an EGR valve and a PCV valve.

 

If that is all it had from the factory, then that is all it needs to have. Emissions output standards for the model year of your truck and the emissions equipment that was on the vehicle when it rolled off the Ford line are the requirements that must be met. In other words, if the vehicle was never equipped with one, it doesn't need to have a catalytic converter. If it had EGR and PCV, they need to be there. It also has to pass the emissions output limitations for 1978 gasoline-engine light-trucks.

Hell, I had a 1969 Cadillac that passed the emissions test for a catalytic-converter-equipped 1982 Eldorado. How do I know? My mechanic is a friend and he "sniff-tested" the car just for giggles and surprisingly, it passed for a much newer car even though it was not equipped with the components that the newer car had. Why did it pass the "sniff test" anyway? Because the emissions standards for 1982 were not stringent enough for the older car's engine to fail the test. Now it would never have passed a visual inspection because it lacked the catalytic converter...and it obviously LOOKED like a 1969 Cadillac (Hearse) and not a 1982 Eldorado. This is the difference between a pass and fail on a "visual" inspection.

 

I see. Thank you.

So when I pull into the testing center they will know that my 78 only has to pass emissions output limitations for 1978? I hope they know....

 

They do. They have a complete database that indicates the OEM setups for vehicles that are still tested. And don't sweat the "sniff test" too much... considering the tale about the Cadillac, the emissions limitations for 1978 can't be all that stringent. If you want to ensure a pass, tune it up, replace air and fuel filters, and give it a good hard run down the highway before you hit the testing center.

 

Appreciate the info!

 

If you have--and it sounds like you do--the original "non-catalyst" sticker, then if I'm reading your state site correctly, the "visual" will be for the gas cap. If it's running right and not burning oil, you should pass the sniffer pretty easy.