Won't Idle

[austinite]

CAR: 1987 300e w124 - 184,400 miles
PROBLEM: Engine starts, but won't idle.
LOCATION: Austin, TX


I can start the car and as long as I keep pumping the accelerator or keep the rev's high (3000-5000rpm's) the engine will run and it will run forever, but as soon as I let up a bit or let it drop to 1000 rpm or less, it will continue to drop to 0 and the engine dies. Not enough time to get the transmission into [D] and actually try driving it.

The car is too old to speak codes to me, I'm told.

I've done all the affordable stuff I know of:

Replaced sparkplugs
Checked Spark
Compression test
Starter fluid test
Sound check for fuel pump
Disconnected flywheel position sensor

Results:
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Spark check: My friend held one of the sparkplugs to the block and got a good shock: good spark but bad boot, but would this stop the car from running?

Compression test: good, range 159psi - 178psi

Starter fluid: Had someone spray starter fluid, while I started the car. Engine ran as long as both the fluid was being sprayed and the accelerator pedal was being pushed down.

Fuel Pump: Heard the 1 second buzz under the car that someone said signifies the fuel pump is working, supposedly.

Flywheel position sensor: I unplugged the sensor from the EZL, the engine didn't even want to turn over until I put it back. Does this eliminate it as a possibility?

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If it means anything, the car stopped working properly without any previous symptoms and without warning. It went kaput when I tried starting it one night, not while driving. I also thought I heard a small single thud coming from under the hood at the moment the problem started.

Thanks for any help,
david