A shortage of vintage emissions parts

March 1, 2012 | By Richard Prince


I have been reading your magazine for many years and have gained a lot of information about a wide range of restoration techniques that will be helpful on my 1940 Ford business coupe that is waiting in the wings.

My current dilemma involves a 1984 Toyota SR5 4-wheel-drive pickup with a carbureted 22R engine. Passing a smog test has become a bit of a nightmare. All the components pass their individual tests but fuel continues to pour into the carburetor. The carburetor has been replaced and double-checked and is working OK. The exhaust system and catalytic converter are relatively new and the O2 sensor is working correctly. All this led me to look into the Toyota repair manual. There I found that there is an exhaust gas temperature sensor (probe) installed into a snorkel tube on the inlet side of the converter. It is connected to the emission control unit. If I understand correctly, the probe is a thermistor that is connected to 5 volts and has a resistance range of 2-200k ohms. This thermistor in turn controls a solenoid linked to the fuel supply line on the carburetor. I have removed the device and checked for resistance between the two wires and do not get any reading that suggests to me there is an open in the thermistor. I also checked for any continuity between the lead wires and the probe case and found continuity from the white wire and the case that would suggest that there is a short. The bottom line is that I think the sensor is bad. Here comes the problem: Toyota no longer carries the part, local auto recyclers don’t have it nor do the online recyclers I contacted. Napa Auto Parts lists it in their stores and online (for $470) but I apparently cannot place an order. I placed an online order three months ago and have had no response except that it will be shipped “soon.” I am without the use of the truck and have nowhere to turn to get the part for what I think is the solution to the problem. I am hoping your resources will be helpful. The numbers on the thermistor’s flange are 065600-1520 89425-35100.


The bad news, Gerald, is that I don’t have a good solution for your problem. Even if I knew of a source for the part you’re seeking I would not call it a good solution if the part costs $470.

I can’t advise you on ways to bypass the device and make your carburetor function well without dumping excess fuel

into the engine because you apparently live someplace where your pickup truck is still subject to emissions testing and that usually means modifying, bypassing or doing just about anything else to an emissions control device is illegal.

Your question does, however, raise a very important issue for many who are or will be interested in restoring and maintaining emission-controlled vehicles well into the future, long after they’ve surpassed their normal life expectancy and long after many of their emissions control parts have been discontinued.

While I don’t think there will be legions of future car collectors worshiping vehicles from the 1980s and 1990s, there certainly will be some. And for every collector there will be many more people who simply want to keep a car or truck from this era on the road and running.

The cost to reproduce many of the emissions parts on old vehicles, in concert with limited demand, almost certainly means that there will be a long list of parts that are simply unavailable.

The solution? I’m sorry to say that I don’t have one. I have often advised people who have a relatively new car that they are in love with and plan to keep forever to invest in some normal wear parts, such as weather stripping, soft trim items, body decals, body emblems, and so on, while correct parts are still available from the original manufacturer. One could do the same thing with emissions parts if they are still available but a problem with that is that the cost for a lot of emissions parts is prohibitive, as the $470 price tag for the part you are seeking illustrates.