I'd been struggling three weekends with my son's 1984 240 (non-turbo gas, LH-Jetronic injection), which was running very roughly and stalling. I could barely keep it running.

The manual suggested lots of things to look at, most of them inaccessible. The last item I checked before I gave up and decided to send it to a Volvo mechanic was the air mass meter. The two resistance measurements suggested by the Haynes manual were well within specs.

However, the tow driver who came to pick it up knows these cars and suggested removing the connector from the air mass meter. Bingo! It started up and ran roughly, but ran.

One visit to the junkyard and $130 later, the problem's fixed. Apparently, the air mass meters can fritz even though the test measurements read OK.

Oh, one other lesson: one of the first things I checked was the coolant temperature sensor, which is buried under the intake manifold, in a location that allows for one hand to reach in, awkwardly, but not get enough grip to depress the wire latch and pull it both. I struggled with that for over an hour before I found that I could put some mid-sized water pump (aka Channellock) pliers on it gently, grab those with my left hand, reach in with my right hand to depress the catch, and yank (with the left hand).

Not sure if it same on the '84's but if the 84 has the Airbox up front with the Airbox Thermostst then I would check it. Usually they fail open allowing hot air from the Exhaust manifold to enter the box. Designed to do this as a preheater but deadly to the AMM if the Box thermostat doesn't funtion.

hate to see you fry another AMM.
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'75 Jeep CJ5 345Hp ChevyPwrd, two motorcycles, '85 Pickup: The '89 Volvo is the newest vehicle I own. it wasn't Volvos safety , it was Longevity that sold me

I checked the airbox thermostat yesterday - you were right, it was feeding air from the exhaust manifold at all times. No more - now it always feeds cold air, while I find out whether the part's still available.

Ah, good. Glad you spent the time to look.

Yes, That Thermostat is available. You can buy it at a dealer OR at WWW.ALLOEMVOLVOPARTS.COM

WWW.FCPGROTON.COM

Any of those. Although Many of us Brickers just disconnect the snorkel tube from the exhaust manifold and just let the cool air run in there. I have notice zero difference for the 3 minutes that the engine runs with very cold air during the winter.
Checking that Thermostat in there is a pain so you can either check it all the time or delete it so you don't have to worry about it toasting your AMM.
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'75 Jeep CJ5 345Hp ChevyPwrd, two motorcycles, '85 Pickup: The '89 Volvo is the newest vehicle I own. it wasn't Volvos safety , it was Longevity that sold me

Thanks. I'll check that this weekend.

I have experienced a stalling problem on the now sold 1983 244. On that car a small split in the induction hose, between the AMM and throttle body, caused the stalling. A $1 used Volvo hose from the self service wrecking yard solved that.

On the 1984 244 my daughter is currently driving, I could not adjust the fuel mixture. Turning the screw in the AMM had little effect. I installed a used AMM of unknown history, and the O2 sensor voltage is ranging from about 0.3 to 0.7 volts.

The coolant temperature sensor should always be checked from the ECU connector. Testing from there verifies the complete connections and the resistance readings.
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john

Bill, I think it is a shame the manuals include those resistance checks to test an AMM. One is to check a multi turn pot (variable resistor) and its wiring to the connector- the CO pot. I doubt one has ever failed - it is just not likely. The other check is said to be a check of the hot wire, but this is not accurate. The resistance you read is really a film resistor used in the bridge circuit to reference the hot wire. The film resistor would be very unlikely to go unless someone shorted out the wiring and made smoke. Besides, the ohmmeters and probes we use are not likely to measure to the tolerances given in the four-ohm range anyway.

A much more valuable indication of the AMM's goodness is its output voltage. Not at idle, where differences in a motor's air needs can vary greatly, but at total quiet rest - no air movement at all.

If you want to try this, for the benefit of three struggling weekends, and so many others doing the same Haynes=Bentley=Volvo AMM checks, backprobe the output voltage - pin 7, the white/red lead, with the ignition on, motor not running. Then connect your old AMM (you don't have to pipe it up) and make the same reading. If you waft a bit of air toward the hot wire, you'll see the AMM functions, increasing the output, but it is the baseline (offset) that is corrupt beyond the ability of the ECU to compensate.

I predict your good one will be 1.6V, thereabouts, and the bad one less than 1.5, possibly around 1.2V, lean enough to keep it from starting.

You could do this, and I'd urge anyone else replacing an AMM would, so that we'd have a better consensus where the marginal AMMs operate.

End of rant.

Thanks for giving me the opportunity to blow off about this, and thanks for the trick of unclipping the ECT connector. There are two styles of this plug, changed around 83-84 from one with a retainer clip that has no release, to one where you have a portion of the clip wire bowed outward, which squeezed unhooks it. Also it is much easier to make the measurements of the ECT sensor from the ECU plug. Clean, no tools needed.
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Art Benstein near Baltimore

Thanks for the feedback.
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Thanks everyone for all the information and advice, Doug C. 81 242 Brick Off Blocks, stock, B21F (non-Turbo), M46; 86 244, B230, 140k , auto.