Hi, folks,
New user, new owner of a 1994 940 NA with B230, 150k miles. Engine is 8valve OHC, I got it from a fella that had blown the head gasket. I had the head completely gone through and milled flat, and am in the process of putting it all back together. I completely removed the intake manifold assy from vehicle so I could get to the air/oil separator and clean it, and am looking at any possible simplifications to make the reinstallation cleaner, and a little less Medusa-like...
I'm wondering if the SAS system is a critical component for emissions or performance or both? Before reinstalling the head and intake manifold, if I can cap this system off and remove the associated hoses then I would prefer that. I don't mind leaving the electric pump in place or remote mounting it to avoid the P0410. I haven't found a very good explanation of the system in my shop manual (Chilton's, so no surprise there...), and since the engine is pre-OBD2, I'd like a better understanding of just how important it is. I also bought a '93 940GLE with the 16valve engine, and though it looks like it has the air pump, I can't see any of the associated piping on the exhaust side of the engine.
I appreciate any insight y'all can provide. Thanks.

 

If you remove it and plug it you will blow the rear engine oil seal. It's easy to install a new one with the head off but not to difficult doing it with the engine assembled.

 

Sorry, I might be getting the nomenclature wrong. I'm not talking about the oil/air separator box, I'm asking about the system that pumps air into the exhaust ports in the head just upstream of the exhaust manifold. There's an elegant little stainless steel manifold under the exhaust manifold with a couple of check valves attached that come up slightly above and to the passenger's side of the front of the head. It's not connected as far as I can tell to the crankcase, so I can't imagine how it could cause the rear oil seal to blow out. Or does the air pump get its input from the oil/air separator?
This system looks kinda like what on an older '70s car that I had was called thermactor air, and it was there to add oxygen to burn any residual hydrocarbons and to help get the catalyst warmed up. Am I misunderstanding the function of this system? If the catalyst is no longer on the car, does the air pump and associated piping serve any other purpose?
Thanks again for the help.

 

OK sorry and I know where you are now. It blows O2 into the exhaust to promote burning of excess fuel. I believe you can unhook it and plug it and I think the O2 sensor will compensate for the system not working. Is it leaking or is the air pump sized? Just try taking off the drive belt and see how it runs.

 

My car actually has what looks like an electric air pump, situated underneath the intake manifold. There's no belt-driven pump. You did bring up an interesting point: does the oxygen sensor see the extra air pumped into the exhaust as the engine running lean and then adds fuel to get to stoic? If so, would disabling this system give me better fuel economy?
I went ahead and buttoned everything back up the way it was. I will probably play around a little bit later with plugging the system, seeing if it sets any fault codes and if the fuel economy changes. I'll post what I find out. Thanks again for the replies.

 

From what you are describing, I think you are referring to the Idle Air Controller. The IAC sits under the intake manifold and has a hose running from the air intake hose and another running to the intake manifold.

You cannot remove this if you want your car to idle properly. Basically, this device meters the amount of air going to the intake during idle conditions. It is controlled by the ECU. During idle conditions, the throttle body is completely closed and this is the only path for air to your engine.

As far as I know of, there hasn't been any blower of air into the exhaust on these cars for emissions purposes. 940s may be different as well as California cars.

 

Yeah, once I started putting this beastie back together, I realized that the hose for the IAC doesn't have any more to do with the secondary air injection than the air/oil separator (PCV)... The supply hose for the secondary air comes from the air cleaner housing. Pretty interesting, since it apparently can only use the venturi effect of exhaust passing across each exhaust port to draw the fresh air in, but I would think it would take quite a bit to overcome the two check valves. There's no provision in the FEAD for a belt driven air pump (and there's also a purpose-built nipple off the air cleaner housing), so I'm assuming this is as-designed.
Thanks again for answering my goofy questions. So far everything has gone back together very well, and all I need to do is pick up the timing belt tomorrow and button up the front end and it'll be ready to start. I love how simple it is, and I'm totally sold on 4-banger longitudinal engines. Don't even get me started about transverse V6's...
I am going to hook the system back up as designed and check the fuel mileage, then cap the SAS off to see if the O2 sensor notices... I'll let you know what I find.