Ok, I did a test using a wireless thermometer from a personal weather station. The thermometer is housed in a plastic case the size of a TV remote control. It appears to sample every few minutes so correlating cause and effect is hampered. Ambient T was about 16 C. I placed the thermometer inside the air filter box upstream of the air filter and near the air intake tube so it should reliably sense the incoming air whether from the exhaust manifold or direct from in front of the radiator. I drove around the city and area for about 30 minutes. The temperature reading peaked at 23 degrees. I then parked it in the driveway and let it idle. Temperature rose slowly to 46 C after about 10-15 minutes idling and seemed to reach steady state. The hood was closed. The aux. fan cut in at one point. I raised the hood and waited for a few minutes. No change in T. I disconnected the intake hose at the manifold and waited a few minutes. No change in temperature. I reconnected the hose and immediately the T dropped to 36 C. I suspect this was just a delayed effect of the slow refresh times of the T sensor. What to conclude?

Well, for one, there is little T rise while driving. Either the valve is a bit open, letting in fresh air (from the high pressure area in front of the rad, or there is sufficient air cooling of the exhaust manifold and inlet hose to keep the T down.

Second, underhood T plays a big role. I would have thought that a properly operating system would draw sufficient air in from the fresh air side to keep the T lower that 46 C. The fact that the T dropped when I disconnected the hose suggests that the valve is stuck and air is being drawn from the exhaust area. The air box was warm to the touch which also suggests that the valve is stuck.

Third, as long as I don't sit idling for long periods (a no-no anyway), I am safe till next summer. Guess I will take the box apart when I get a chance.

Thanks everyone.

Bill

Regina has no AMM to cook. So assuming that none of the other sensors are in danger from the hot air (MAP is far away, only connected by a tube), does anybody have any thoughts on continuous hot air coming in.

I know cold air is denser, and so it can be a performance issue if less dense air (and so less oxygen) comes in. In the case of my commuter performance is not a big issue. I also live in Minnesota, so for much of the year, it isn't a choice of room temp air or hot air, but rather, cold air or hot air.

How could hotter air all the time effect gas milage? Any other considerations?
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Andy in St. Paul. '89 244 153K mi, '91 745 Regina 206K, '88 244 184K

Point a hair drier at the thermostat. Within a minute or two or three the thermostat valve should fully close the air flap over the warm air intake. If not then either replace the thermostat (avail cheaper in the aftermarket) or disconnect the air hose (though some well meaning soul is likely to put it back on) or screw the flap shut. The black heads of a couple of short drywall screws driven in from the outside of the box will not be noticed by emissions inspectors. Whatever you do, attend to this soon as your AMM can get cooked.
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Dave -own 940's, prev 740/240/140/120's & quasi-expert only on a good day

If temperature outside is cool, it would keep the flap on the exhaust side. I think the thermostat turns the flap if outside air is about 20-23 C. I actually have fix the flap in my Volvos permanently open to fresh air only. The hot air from exhaust does not improve much of anything to be worth the risk of burning a MAF sensor and a power stage in 960 models.