Topic: Air Injection Gear---GONE!
in Forum: C3 Fuel, Emission Control, and Exhaust Systems
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Well, that's the exact tube that was left "open" when I installed my new catalytic converter. Dave, what I did was remove the entire assembly. It's just a matter of taking off the two or three clamps holding it to the exhaust downpipe, detaching the hose clamp around the manifold and then removing it from the diverter valve at the other end. You then cap the AIR tube at the converter and insert a 1/2" hole plug into the diverter. I guess the code might have come from a strange O2 reading, but I have not had any problems with mine thus far. You could even go as far as disconnecting the AIR pump drive belt and plugging the vacuum lines to the TB, effectively eliminating the smog equipment altogether. PSU 98 2008-01-14 02:16:53
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Stephen,
I know a lot of owners have removed all the emissions equipment, but I think I'll see what it will cost me to keep it all functioning, then decide.
Thanks everyone.
Now I know what to ask for.
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Lifetime MemberHey Dave, I have that tube with the check valve, you can have it. I just moved it from the garage to my shed yesterday.
DaveM 2008-01-14 10:27:24
That would not throw a code, it has nothing to do with the O2 sensor, which is before the cat. That whole A.I.R. system can be removed without affting the computer. If you want to keep it stock, I have the parts from mine, and if you can have whatever you want.
Dave
Lifetime Member #116
Dave's '82 
I don't need the pipe but I could use the check valve. See if you can unscrew it from the threaded end of the pipe without breaking it.
I'll try the same on mine.
I'll take the other parts as well. Let me know what the shipping cost will be.
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Hard to believe, but AutoZone has the check valve. It's one of only about three designs used on all of the GM AIR systems. Very common. You may need to heat the old one to get it off of the pipe.
The only purpose of he system is to reduce emissions, it will not affect the way the engine runs at all, WHEN THE SYSTEM IS SEALED.
When open, like yours is now, it allows the exhaust to leak, and sucks air into the exhaust system, which messed with the oxygen sensor readings causing the check engine light to come on.
Ken, the check valve his is refering to is the one that goes to the cat. converter, if any air is sucked in it will be into the converter, beyond the O2 sensor.
If it was one of the other check valves (exhaust manifolds)then what you said would hold true.
I know, picky-picky.
Lifetime Member #116
Dave's '82
Due to the vacuum pulse effect of the exhaust system, any leak entering the system can affect the oxygen sensor as much as 18 inches upstream of the air entering the exhaust. With the converter within 18 inches of the sensor, it can still have some effect.
An object in motion tends to stay in motion. When the exhaust valve closes, the rapidly moving gas trys to keep going when the valve shuts, and a vacuum is created. This pulse is present the entire length of the exhaust system, but only pulls air back in a max of 18 inches. At low engine speeds the length is less.
Yep, picky.
With that small a change would-en the computer arverage it and adjust as needed? I did not think it would throw a code.
It's the Engineer in me picking your brain.
Dave
Lifetime Member #116
Dave's '82
It depends on how far it has to adjust. The computer in those years throws three different codes for the O2 sensor.
44 - System lean. This is when the average stays under .45 volts, the switching point for the O2 signal.
45 - System rich. Stays over .45 volts
13 - Oxygen sensor inactive. This one can vary. It is either no signal from the sensor or it is not going out of the dead band.
The total range of the sensor is 0 to 1 volt, with .45 being the switching point.
The sensor must create Cross counts, which is how often it crosses the .45 V line. It must also go out of the dead band, which is from .3 V to .7 V. If it does not pass these points, not every time but frequently, the computer believes the sensor is getting worn out.
When there is nothing from the sensor there is a .45 signal on the sensor line, even though the sensor, when active, transmits a voltage. The computer uses this voltage as a reference to base the system on when in open loop. Once the sensor becomes active, the signal from the signal is much stronger amperage than the reference signal, and overpowers it with it's voltage signal. A shorted sensor will maintain 0, but not a dead one, that will stay at .45
The sensor is really a battery with Zirconia as a acid, and sandwitched between to plates forming the sensing thimble that is in the exhaust flow.
Air is allowed on the inner plate, and exhaust is flowed over the outer plate. The difference between the two plates is a result of oxygen being present in the air, or lack of oxygen in the exhaust. The richer the exhaust the less oxygen it contains when the engine is running properly. When it leans out, the oxygen content in the exhaust rises, and the plates become more similar, reducing the voltage output of the "battery".
It won't average the signal per say. What it will do is change the command to richen or lean out the mixture to make the signal average the .45 while exceeding the dead band and maintaining good cross counts. As it reaches the limits of it's adjustment or cannot achieve proper voltages, it sets the code.
So if it will set a code or not depends on several things. Engine rpm is one of them, it affects the pulse rate of the vacuum pulses, which will affect the air flow. Throttle position will also affect the exhaust volume. Throttle is not related to RPM. It affects rpm, and to some extent controls it, but does not fully control rpm. The blend of the two become important to the pulse effect and volume drawn in to the exhaust.
Another factor is the temperature of the sensor. It starts to become active at about 585 deg F. Full operation happens at 600 deg F. and above. Newer sensors have heaters, but the older cars rely on exhaust heat, which is greater with more flow, but rich tends to run a bit cooler.
If the car has been driven at a moderate rate, or cruise, the sensor will be very active. At low rpm or idle the sensor can cool off enough to become inactive.
So the answer is a blend of all of the above as to when the sensor is active enough, in the right ranges, and under flow conditions to set the code.
Yes I have seen that condition set a code, but the age and conditon of the sensor is another factor, and sometimes the same conditon will not set the code.
Thanks Ken, that kind of detailed info is hard to come by.
Thanks again,
Dave
Lifetime Member #116
Dave's '82
in Forum: C3 Fuel, Emission Control, and Exhaust Systems
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