What was the worst emissions control device?

Was it the A.I.R. System? The Chrysler lean burn?

My vote…

Diesel particulate filters.

They might work well on vehicles that are run on the highway most of the time, but ambulances, bucket trucks, in town delivery trucks, they are terrible.

We have a f-550 at work with a DPF and it tries to clean the filter at inopportune times, Often you have to go for a joyride for 10-15 miles to clean it. You waste a lot of fuel and if you interrupt generation by taking the truck out of gear, it will belch smoke for a while before going back into regen.

They clog frequently when not used under ideal conditions…

They should have never been put onto vehicles that have to idle a lot, or they should have made bucket trucks that were made to shut down the motor and run the hydraulic pump off of a battery.

Early air pumps that were added just to after burn enough exhaust to pass emissions. They killed motor performance. Good riddance to air pumps…hated them !

I nominate the rat’s nest vacuum systems used by makers trying to avoid the fuel injection fees by modifying carbs with layer upon layer of add-on systems. Each hose and connection is a candidate for both leaks and misconnection.

Two systems IMO. Carbureted Hondas with the 14 miles of vacuum hose and dozen or so solenoids per car and CIS fuel injection on some of the Euro cars.

My vote would be either for the early air pumps or the early computer-controlled Rube Goldberg carburetors that a lot of manufacturers used in the early 80s. Cranking back the compression and ignition timing so that a big-block V8 struggled to make 200 HP also sucked big time.

Due to personal experience, I have to say Chrysler’s electronic lean burn. My mother used to have a '87 Dodge Diplomat with the lean burn 318 and electronic feedback carburetor. At the same time, I had a '87 Ram half ton with the non-lean burn 318 and standard two barrel carb. My truck never stalled and had an abundance of power and performance (to a 16 year old, anyway), which is two things that could not be said about my mom’s Diplomat. That car struggled to get out of its own way, had to be driven with two feet to try to prevent stalling, and even then would often have to be re-cranked 20 or so times during the six block drive my mom took to work every day. I had read an article in a magazine about bypassing the lean burn system, installing standard electronic ignition, and a non-electronic carburetor, and having a decent running car afterwards, but was never able to convince my dad to give it a try. He had all the necessary parts in the garage, but refused to convert it on grounds that the factory made the car a certain way for a reason and that it was the way the car was intended to work, so changing anything would be a bad idea (I thought it was a great idea). The car was junked before its time due to the constant stalling and my mom’s health preventing her from driving a car requiring one foot on the brake and one on the gas all the time. I feel bad for police departments that had to use these gutless, stalling nightmares.

@dagosa Yes, I’d have to go with the “smog pump”. Our Granada had one and when it failed, we never replaced it. The car ran better without it.

Count my vote for the smog pump. If I bought a vehicle with one…it was removed and plugged by the weekend (my own vehicles only of course).

Those smog pumps were also a pain to replace. I had to replace one ONCE. Never again.

It’s been a constant race between the regulators who set limits almost arbitrarily and the manufacturers who figure out how to get under the limit without spending one more dime than they have to.
In the '70s the manufacturers were struggling to keep up, so performance, reliability, durability and serviceability often took a back seat.
It didn’t help that a big American sedan couldn’t emit any more grams per mile of pollutants than a little Japanese import.
Many of us here are kind of afraid of electronics and computers, but advances really turned things around beginning in the '80s.
Not only control systems but also computer aided design improved things like combustion chamber shape and cam profile.
Does the modern Dodge “hemi” engine really have just a simple hemispherical combustion chamber? Probably not.
I wouldn’t be surprised if a modern car could meet the 1975 emission limits without a catalytic converter.

“Does the modern Dodge “hemi” engine really have just a simple hemispherical combustion chamber? Probably not.”

Nope, it’s more of a ‘semi-hemi’. A full hemi really isn’t the most efficient way to go, what with fuel injection, and the need to minimize the surface area to volume ratio…


Just some worthless trivia, but Harley has had production hemis since 1936 (excluding the 1935 prototype and '36 up sidevalve models) and still use them today with fuel injection.

You ask what the worst emissions control device ever is?
IMHO it’s the Supreme Court of the US. They have blessed the right of the EPA to regulate whatever they want, regardless of the Clean Air Act. And to whatever level. Now I see in the news that the Prez is going to raise the mandated levels through executive edict. With no need for science, no need for review, no need for technical people. No need to amend legislation. And who will stop him? SCOTUS? I don’t think so.

There was a device that some salesman convinced the California legislature back in the early 70’s should be retrofitted on all older cars to reduce emissions. All it did was interrupt the vacuum advance unless the engine started to overheat. Every car owner in California was required to buy one of these devices, then they found out it didn’t reduce emissions at all, just reduced everyones gas mileage.

Even cars coming out of the factories were required to have these installed.

It must be something in the water out there in Cali that makes them do ridiculous stuff like that

Smog pumps and EGR valves…

But I can’t complain…We sure made a lot of money removing them and blocking off the various ports…De-smogging we called it…

One of the worst individual parts I’ve ever had the misfortune to put up with was the mid/late 80s Subaru ASV widgets. (Air Suction Valve)
These essentially fed heated exhaust gas into the air cleaner housing and were screwed up all the time. There was even a recall on them that paid .2 hours to do and sometimes took 2 hours as that large exhaust pipe screwed into the cylinder head exhaust port would balk at coming loose.

Apparently no one in the design or assembly stage of this wheezing junk ever considered the effects of hot exhaust soot on an air filter and throttle body.


There was a device that some salesman convinced the California legislature back in the early 70's should be retrofitted on all older cars to reduce emissions

You have got to be kidding. I am all for clean running vehicles, however its got to work. Most of the 70’s hubub were junk.

IMHO the dpf systems on diesels is a joke. They are nothing but trouble.

@WheresRick, @keith is right. Ignition timing advance combined with high compression engines results in good performance but lots of oxides of nitrogen (NOx) emissions. Before EGR valves and catalytic converters the only way to reduce NOx was to reduce compressions and use less ignition timing. So, as part of the CA smog program, cars made from 1966-1970 were required to have a “NOx device installed”. Dad had a nice 69 Skylark with the high compression engine and 4 barrel carb. I remember being a kid and listening to him complain that his car ran like crap now. He finally took it off himself.

As for EGR valves, on a modern day car they improve performance, not detract from it, as long as they’re working properly. But on a mid-70’s Ford they were nothing but trouble.

I think most emissions systems suffered early development problems. I have to shake my head when I remember all the rotten eggs we smelled back in the early '70s. And all the dieseling that went on when we shut our cars off.

I have to believe that the EVAP systems are currently the worst. The standards have been tightened to where unresolvable leak codes are too common. The only benefit I’ve seen is to the guys who make gas caps…which rarely solve the problem.

EGR systems are disappearing with the variable valve timing becoming common. Designers now are beginning to simply retard the exhaust valve leaving a bit of inert gas in the cylinder to keep the cylinder temps down. I guess it must work.