Why do "gen 3" s series have air pumps
- Thread starter ram_man
- Start date
- Status
I think what you're hearing come on when you're stopped is the cooling fan not the air pump.
The air pump is used briefly after a cold start to add air to the exhaust stream. The extra air in combination with the unburned HCs you get from a very rich fuel/air mixture get the Cadillac inverter up to operating temperature quickly.
The air pump is used briefly after a cold start to add air to the exhaust stream. The extra air in combination with the unburned HCs you get from a very rich fuel/air mixture get the Cadillac inverter up to operating temperature quickly.
JHZR2
Staff member
S series like s-10 trucks?
I have no idea what he is talking about and my crystal ball is frozen ....
Originally Posted By: yonyon
...get the Cadillac inverter up to operating temperature quickly.
...get the Cadillac inverter up to operating temperature quickly.
Originally Posted By: ram_man
sorry Saturn people know what s series means.... I assumed everyone has heard that by now. s series are the Saturn line the sl sc and sw.
well thats true when you post on a saturn forum.. its pretty easy to guess its about a saturn.
when you post to a general forum. We dont memorize everyone's car.. you could add them to your profile..
sorry Saturn people know what s series means.... I assumed everyone has heard that by now. s series are the Saturn line the sl sc and sw.
well thats true when you post on a saturn forum.. its pretty easy to guess its about a saturn.
when you post to a general forum. We dont memorize everyone's car.. you could add them to your profile..
Originally Posted By: ram_man
the cooling fan isn't coming on when I hear it. its the air pump you'll hear it when the car isn't warmed up and you stop . so take off drive 1/2 mile stop and idle it'll come on.
I didn't know it did that. Here's some pure speculation:
If you're in the habit of driving off immediately after a cold start the PCM wouldn't otherwise get to check for proper operation of the AIR pump. If checks the AIR pump by watching for the upstream oxygen sensor voltage to go low when it commands the air pump on.
The PCM has to be programmed to check these things in normal use. If it didn't, that would be a big problem with using OBDII as an emissions test. Normal use could include a cold drive off every time so there should be some opportunity for the PCM to turn the air pump on as a test. It needs to do this with the engine at idle because the pump doesn't push enough air that it would necessarily force the O2 sensor voltage to read lean as you're driving.
Again, I'm just speculating here but it's the only explanation I can think of.
the cooling fan isn't coming on when I hear it. its the air pump you'll hear it when the car isn't warmed up and you stop . so take off drive 1/2 mile stop and idle it'll come on.
I didn't know it did that. Here's some pure speculation:
If you're in the habit of driving off immediately after a cold start the PCM wouldn't otherwise get to check for proper operation of the AIR pump. If checks the AIR pump by watching for the upstream oxygen sensor voltage to go low when it commands the air pump on.
The PCM has to be programmed to check these things in normal use. If it didn't, that would be a big problem with using OBDII as an emissions test. Normal use could include a cold drive off every time so there should be some opportunity for the PCM to turn the air pump on as a test. It needs to do this with the engine at idle because the pump doesn't push enough air that it would necessarily force the O2 sensor voltage to read lean as you're driving.
Again, I'm just speculating here but it's the only explanation I can think of.
sounds plausible to me. my tundra runs something like this for the first minute of cold start. I've never noticed it before in any previous vehicle I've had.
The minivan has an air/vacuum pump as well. I think it pulls a vacuum on various emissions circuits every once in a while, as it seems to correspond with CEL when something is wrong.
The minivan has an air/vacuum pump as well. I think it pulls a vacuum on various emissions circuits every once in a while, as it seems to correspond with CEL when something is wrong.
Air pumps tend to appear on older, dirty engine designs to cobble them through passing newer stricter emissions. They're complicated and probably a warranty hassle, so "clean paper" designs try to avoid them.
At 197k, my 2000 saturn is doing fine with the air pump; never a problem. They say Trailblazers get water in the air pipes that freezes or otherwise screws them up, so not every design is infallible.
However, the pre-cat manifold gets wicked hot and I have a broken exhaust stud on the downpipe. Believe the heat acellerates corrosion as I've gotten older models apart flawlessly several times.
At 197k, my 2000 saturn is doing fine with the air pump; never a problem. They say Trailblazers get water in the air pipes that freezes or otherwise screws them up, so not every design is infallible.
However, the pre-cat manifold gets wicked hot and I have a broken exhaust stud on the downpipe. Believe the heat acellerates corrosion as I've gotten older models apart flawlessly several times.
If an engine has to run extra rich, an air pump adds enough air to balance the air/fuel ratio. If the car uses a cat, the extra heat generated by the process shortens catalyst light off time. Some cars simply need them operating continuously because they don't burn fuel well at all, but that typically applied to 1960s designed engines that the manufacturer wanted to keep producing. The last of the Ford SBF, BBF, and I6 are the first examples I can think of.
It seems every modern German car I have worked on has an electric air pump, even ones with cutting edge technology.
It seems every modern German car I have worked on has an electric air pump, even ones with cutting edge technology.
- Status
Similar threads
