You’d have to have a gadget that measures tailpipe HC’s
You already have that. That’s why they use an after cat oxygen sensor. It indirectly measures HCs by reading O2 concentration. If O2 isn’t making it out of the tailpipe, there’s likely HCs coming out that didn’t get fully consumed by the cat(s).
Perhaps you recall the early days of emissions testing. They used a mass spectrometer to sniff the tailpipe gases looking for HC count. Now they rely on the onboard sensors. Look at cars cosuming quarts of oil every 1000 miles. In the old days, they would be mosquito foggers. Now, with modern cats and sensors to monitor performance, you can’t even tell they are eating all that oil. It gets consumed in the cat(s). PCV blowby? peanuts in comparison.
@Sloepoke, thats how I did mine. The issue was not having very much room to turn the wrench, only a few degrees at a time until I got it loose enough for the ratcheting wrench. New one went in easy, but the old one gripped the threads all the way out, it never got loose.
I never thought the slant six was hard to work on. To put in points and a condenser I just pulled the dist. and put it on a picnic table. Had no driveway or garage back then. You could change the starter standing up with a crescent wrench.
If you wanted a job that was a pain, they adjusting the valves on the flathead sixes that preceded them.
Anyone remember air injection systems - pumping air into the exhaust stream at the exhaust manifold? The official explanation was that introducing air at that point helped hot HCs to burn. Another explanation was that the air simply diluted tailpipe gasses, so the tailpipe emissions fell below the allowed concentration. Kind of like building higher smokestacks - "dilution is the solution to pollution."
The air injection system was created because the hot exhaust gases still contained unburned hydrocarbons, but had no available oxygen for them to burn with.
By injecting air up near the exhaust manifold, those red-hot exhaust gases got the added oxygen it needed to more thoroughly burn those hydrocarbons.
@joeMario My 1976 Ford Granada with a 351Winsor V8 had that system, powered by a “smog pump”. This engine was hard to clean up and the air injection was a feeble effort to achieve compliance.
The carbon steel pipes quickly rusted through (just after 50,000 miles) , and the units on the shelf at the dealer already had surface rust on them. I thought about fixing it when the pump failed as well., after which I just had someone plug up the injection ports and took off the whole system. No problems after that.
This car had a catalytic converter, by the way.
My decision was aided by Thoreau’s Essay on Civil Disobedience. If the Law is an ass, and the manufacturer is allowed a shoddy fix, I have the right to act sanely and in my own interest.
The air injection systems are still around, only its called secondary air now. Fuel injection pretty much did away with the need for the air pump except when the engine is cold.
after the engine has run for 10 seconds or so from a cold start, the exhaust gases are hot enough to burn the additional fuel needed by the cold engine.
The secondary air pump is electrically powered now and it runs from about 10 seconds after start to about 2 minutes when the fuel injection returns to a leaner A/F ratio.
One of the issues with the old air pumps was the little steel pipes that blocked about a quarter of the exhaust manifold passages. I learned through some magazine article that after testing, it was discovered that the air injection system worked just as good without the little tubes blocking the exhaust, so I removed them in my cars that had them. The air pump was still hooked up so I didn’t have any trouble passing smog checks, even in California.
The Trailblazer has an A.I.R. pump on it.
Depending on ambient conditions and how cold the truck is, it will run for up to 5 minutes based on my observations. The purpose is to get the cat lit off as quickly as possible by injecting additional oxygen into the exhaust stream. Coupled with a slightly rich exhaust, it shortens the time before the cats are up to working temp.
I remember when “smog pumps” and catalytic converters were being removed. You could buy plug kits for exhaust manifolds and “test pipes” to fill the cat gap.
I am glad the days of the smog pump, etc. are over. I haven’t messed with many of these as they were before my time but it seems like modern tech has made engines cleaner burning and more powerful, eliminating their need.
This thread reminds me of a common issue on the 3 cylinder Geo Metros. These were a cheap car from the start and haven’t been made for a long time so it is very common to get severely neglected ones. Some appear that the oil has only been changed a few times in their existence. The first engine in one of mine fit this category. The blowby in these can pressurize the crankcase to where oil in the head cannot return to the sump through drain holes. Eventually it reaches the level of the PCV/breather baffles and floods past, sending a cup or more of oil right into the intake. The engine sputters and releases a MASSIVE cloud of mosquito fogging smoke. Mine was doing this under load when I was climbing large hills at highway speeds. I actually saw cars pulling over to the side behind me and am sure there were plenty I couldn’t see doing the same. The Metro people refer to this condition as an “oil fart”.
It is funny but one of the ways to “rig” an engine so it doesn’t do this is to raise the dipstick a tad so the excess pressure can escape that way. I found a good used engine but many run around like this for years and never have any issues.
I think my problem was caused by the engine having a bypassing air filter for a LONG time. The intake was full of rocks, sand, and other grit and had been this way for who knows how long. I am sure the rings/cylinder walls were scoured beyond hope so went for the replacement engine. I tried a couple snake oil type flushes and I think they dissolved whatever crud was holding the engine together and only made the problem worse. One of these “oil farts” burned over a quart of oil in one shot towards the end. I wonder if the engine would have even stayed running had it not been in gear with the forward momentum of the car to keep it turning.