My '88 had similar symptoms, and it turned out to be two things: vacume lines had cracks, and the electrical contacts at the injector had corrosion causing intermittent misfiring.
Worth a look before you spend real money on mass meters and O2 sensors.

Rough idle, low power, and hesitation. Could be lots of things.

Have you looked at the timing belt? If it has jumped a tooth, that would give the symptoms you describe.

Check your ignition timing, has it jumped off?

Also, you might consider an exhaust obstruction, though that would not generally impact idle. Catalytic converters can plug the exuaust flow when they fail. Put your hand at the exhaust outlet. You should be able to feel the individual bursts of exhaust.

I have an '89 244 like yours. I had a bad 02 sensor last year and it gave me a bunch of symptoms, but it was only slightly rough running and then only when the engine was all the way heated up. Gas milage was bad an plugs were getting fouled because it was running very rich. I had a big problem getting the old sensor out, so I wound up unplugging the sensor and found that it ran much better in the meantime that way.

Is your check engine light on? Have you checked for codes in your On Board Diagnostics box under the hood? If you don't have any codes, I wouldn't think it's a sensor.

Besides vacuum leaks, I would think you would want to clean your throttle body if you haven't done so lately, or never have. That would give you a chance to check most of the vacuum hoses, make sure all the vacuum ports are clear, etc.
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Andy in St. Paul, '91 745 Regina 198K mi, '89 244 142K, '87 245 RIP

The car should start and run fine with the Air Mass Meter unhooked. If it does, or runs better than with it connected, you need a new one (another new one?). Model 016 AMM. If it's bad, it won't run right on the highway or at full throttle, it'll die. May recover and then idle fine after.

I'd look for some other fault causing weak spark. Possibly a bad ignition power stage, or a dying coil. Dist cap and rotor look fine, no carbon tracking? I know you said they're new- just make sure. If hte engine was washed, water can get in there.

Other than that, there would have to be a problem with fuel delivery- a split in the hose for the in-tank pump, a bad main or in-tank pump, plugged fuel filter?

Some things to work on anyway. Good luck!

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Rob Bareiss, New London CT ::: '87 244DL/M47- 234K, '82 245T/M46-182K, '84 242DL/AW70-100K, '89 244DL/AW70- 212K and I miss my: 86 244DL 215K, 87 244DL 239K, 88 744GLE 233K, 88 244GL 147K, 91 244 183K