So, I think my car has this, but I havent heard anything about it before, other then the fact that it can be cleaned.

Thanks and Happy Bricking!

Excellent information has been posted so far. I'll add one little bit of information that will help you identify the Idle Air Control Valve (aka: Constant Idle Speed motor) unit that you have in your vehicle, and also help you in locating a replacement (used) unit from the other vehicles it was shared with.

This should be a complete listing of IAC Valve part numbers and the years that they were used in the 240 cars (and a few 740/760 vehicles). For simplicity sake all 4 of the IAC valves have the part number 0 280 140 ###, and I will list only the last 3 digits. (500, 501, 520, 516)

Bosch 500: 240 '81-'82 and 240 Turbo '81-'83.
Bosch 501: 240/740 '83 through April,'87, also 240/740 Turbo '84 through April,'87.
Bosch 520: 240/700 May,'87 through all of 1988.
Bosch 516: Most late model 240 and 700/900 vehicles with LH 2.4 & 3.1 Fuel Injection (1989+). Note, many late model turbo vehicles still use the 520 (I own one of these such vehicles).

The Bosch 520 was slowly replaced by the 516, and I would list more specific dates, but my information is somewhat limited. The dates listed for the 516 in the IPD catalog seem to be incorrect in many cases and I think they may have mixed up the 516 and 520 in several of their listings. -I have seen evidence of this on several occasions.

FYI, if you are in need of either a Bosch 501 or a 520, be advised that these units are interchangeable. The 520 replaced the 501, but they are essentially the exact same unit. Volvo doesn't carry the older 501 units anymore, but they'll happily give you the new 520 to replace your 501 when you order a replacement part. For the sake of completeness, the Volvo part number for the old 501 unit was 1317957-7, and the new 520 part number is 3517067. When you try to enter the old 501 part number into a VADIS database to order the part, it will automatically change into the new 520 part number.

For identification purposes, the 501 and 520 units look identical and you can see a picture of one on page 41 of your Fall-2003 IPD catalog (looks like a silver "T"). The Bosch 500 units somewhat resemble a large Ice Pick, and the late model 516 units look similar to the 501/520 units, but the valve assembly is different and makes a 90-degree angle turn between the inlet and outlet ports.

God bless,
Fitz Fitzgerald.
--
'87 Blue 245, NA 231K

In a set of odd circumstances, a perfectly good 516 just fell into my lap (out of a dead 91 740t). I have a 86 740 n/a-- can I replace the 501 it has with the 516, if the 501 is indeed bad? Are they compatiblle (2.2 - 2.4 issues, I assume)?

Are the 501/520 and 516 units compatible? I'm not sure... Aside from the hardware differences (air tubes input/output), there may be other internal differences. I haven't yet had a chance to dismantle a 516 and compare it to the 501/520 yet.

Hopefully someone else knows and can answer your question. -and hopefully sometime in the next year I'll have the chance to pull one apart and compare them for myself.

God bless,
Fitz Fitzgerald.
--
'87 Blue 245, NA 231K

After performing a tune up on a friend's '90 240, I've had a chance to further inspect a 516 IAC Valve and it's associated plumbing and two major differences are present. I've outlined them below:

The 501 and 520 IAC valves require electrical power to both open and close the valve. The 516 is spring loaded and power is supplied only to Open the valve, and it snaps shut when power is disconnected. The other major difference is that when a 516 is closed, it isn't really completely closed. It is still open slightly and alows a predetermined amount of air to pass through it. The '90 240 that I was working on did not have an Idle Speed Set Screw (black thumbwheel) on the throttle body, and it would seem that the 516 has eliminated the need for one.

To answer your question: "Can a 501/520 be swapped with a 516?" I'm sorry to say the answer is no.

God bless,
Fitz Fitzgerald.
--
'87 Blue 245, NA 231K

Under electronic control it accomplishes the same thing as your right foot used to do on your old carbureted Chevy or Ford - continuously adjusts the air going into the engine to keep it idling. It bypasses air around the (closed) throttle valve, and it only operates when the throttle position switch signals that the throttle is completely closed. Properly functioning, they are unnoticeable, and the engine idles steadily under all conditions. Gummed up, it typically stalls the engine after a cold start, or it almost dies, then revs up and down a bit trying to find the right speed.

A secondary and little-known function is to prevent manifold vacuum from getting too high under closed-throttle-high-engine-speed conditions, such as going down a hill with your foot off the gas. Not sure why this is necessary on an EFI engine, but some emissions-controlled carbureted engines had little spring loaded valves incorporated into the throttle plates that would open under high vacuum to accomplish the same thing. This prevented excess fuel being drawn in with a resulting emissions increase.

Non-Volvo Trivia: most of us owners of later MGB's with these throttle plates install pre-emissions plates or solder the valves shut, as they are a total PITA in terms of ever getting the engine to idle right. Probably create more pollution than they ever prevented.
--
Bob (81-244GL B21F, 83-244DL B23F, 94-944 B230FD plus grocery-getter Dodge minivan, MGB, and numerous old motorcycles)

On my 81 it sits above the intake manifold, more or less centered. Same cylindrical shape.
--
Thanks to everyone for the help, Doug C. 81 242 Brick Off Blocks, stock, M46; 86 244, 140k , auto.

Doug that device also bypasses the throttle valve, but it is called the "auxiliary air valve" and is not controlled except by conduction and electrical heat. It is more or less like the fast idle on a carburetor. An IAC valve is under computer control and is used for warm up, base, and load idle control.

My son's 81 has the auxilary air valve (Air Slide?) with two wires (like you describe), no Coolant Temperature Sensor, and no throttle micro switch.

My 81 has and Air Control Valve with three wires that go to the ECU, a coolant temperature sensor, and a throttle micro switch.

The cars take different wiring harness even though they are the same year. We learned that last summer when we did the two harnesses.

When people say Idle Air Control Valve, aren't they talking about the same thing the Green Book calls the Air Control Valve? I'm learning as I go on all this electrical stuff.
--
Thanks to everyone for the help, Doug C. 81 242 Brick Off Blocks, stock, M46; 86 244, 140k , auto.

I don't have that green book Doug. The early K-jet auxiliary air valve, is a slide valve like you say, normally bolted to the edge of the cam cover. The wires are for a heater circuit. Conduction and the heater expand a bi-metal strip that closes the slide as the engine warms up. It is a cold fast idle device. The Idle Air Control valve is plumbed similarly into the intake tract, but it controls idle speed constantly through feedback. So it does the cold idle, and hot idle, and compensates for loads like AC and steering. It replaces the AAV and does more, so its wiring is from the computer, and is a true output device.

Yes, and on our '81 K-Jet it is definitely "computer" controlled - by a separate electronic unit mounted near the Lambda-sond ECU. Not sure when Volvo made that change on the K-jet engines, but the "CIS" stands for Constant Idle System or Constant Idle Speed...something like that.

Many people think it means Continuous Injection System (which is what K-jet does, true enough). Volvo used the letters "CI" to refer to the K-jet continuous injection. A little confusing!
--
Bob (81-244GL B21F, 83-244DL B23F, 94-944 B230FD plus grocery-getter Dodge minivan, MGB, and numerous old motorcycles)

Bob it's true in North America that CIS does stand for Constant Idle Speed. When Bosch first used the term in the 70's though, they intended it to be the English term for what they called the K-Jetronic system. In German, it is spelled "Kontinous", hence K-Jet, with "CIS" meaning "Continuous Injection System". When OBD II systems came out, the terminology was also standardized, so Bosch was told not to use CIS to describe their fuel system, as that acronym was to be applied to all cars as constant idle speed. Now it seems that IAC has superceded it.
More info than the topic warrants I suppose.
I think the electronic part you are referring to must be the frequency valve, which no Canadian market B21 or B23E engines got, only the American market cars. Other engines using K-jet did get frequency valves, like the B27, and VW and Mercedes in the Canadian market.
It is confusing!

idle air control.
it bypasses the throttle plate when its closed (foot off gas, ideling) by opening a valve on a small tube coming off the air intake before the manifold. it then utilizes a single separate injector providing the correct mix of fuel and air.
its located beneath the intake manifold.
--
1990 740 turbo sedan

There is no fuel (or injector) associated with the IAC. It regulates idle speed soley flow.by controlling throttle bypass air
--
Bruce Young,
'93 940-NA (current), '80 GLE V8 (Sold), '86 240dl, '85 244 ti, '83 245t
'76 244 (R.I.P at 255k), 73 142 (98K), '71 144 (ex circle track car)
Used '70 144 from '78 to '92, New 144 from '67 to '78, Used '62 122 from '63 to '67

It is the "idle air control" valve. It sits below the throttle body, and ahead of it, and is a small cylindrical device. It controls the amount of air bypassing the throttle plate to allow the computer to set and compensate idle speed. Two hoses and a wire connection on it.