1995 BMW 540I starts well cold, then dies out after getting to normal operating temperature. Usually will not restart until cools for a long time..cranks but won't start....Jack

Bad coolant temp sensor making ECU think engine is still cold, thus running rich, as if choke is on. There are two temp sensors, one for dash gauge (one wire) and one for the ECU (two wires). You can remove it and test with voltmeter by placing unit in hot or cold water to compare readings.

This is usually a problem caused by a bad water temperature sensor. There are usually 2 sensors with one working the temperature gauge and the second working engine controls.

The "cold start" sequence is similar to a choke in old cars. It needs the signal from the water sensor to trigger the cold start sequence. The cold start sequence enriches the fuel charge, adjusts timing, and increases idle speed until the engine gets a little warm.

Now if stalling when warm, you have other issues. Manifold runners are a problem on some engines.

Your vehicle needs a signal from a Temperature sensor to activate the "Cold start routine". The cold start routine is a modern day version of a choke used in the old days. This process will make the engine speed up by enriching the fuel mix and resetting the engine timing.

The problem is that your engine is stuck in the normal "Lean" run position for better mileage and lower emissions. There can be 2 temperature sensors in each vehicle with only one dedicated to operating the engine controls. The other sensor would operate the dash gauge or light.

When the Temperature sensor is replaced, the system should work again. If it does not respond, there could be a connector problem in the PCM unit, but it is less likely.

The onboard diagnostics would generally monitor the PCM, but the Temperature sensor is usually an unmonitored device.

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Check the coolant temperature switch. Maybe faulty

You probably have a bad ignition module located directly under the ignition coil packs-a common issue on Saturns.

Are there any service engine soon lights on associated with this problem?

Possible CTS (Coolant Temperature Sensor) or another sensor giving faulty data for the cool air temperature.

Check spark and gas delivery when cool, below 70 deg. If the spark is not being delivered or the fuel injectors are not delivering fuel at this temperature, it will explain why it doesn't run right until it is warmed up.

replace the crankshaft position sensor.

possibly the coolant temperature sensor is faulty

check engine coolant temperature when it gets warmer, or at operating temperature, and verify that the temperature gauge is showing warmed up to operating temperature. If the coolant temperature sensor tells the computer the engine is cold it will over fuel and miss and the engine will die. When cooled down it will run fine until it warms up. Also could be coil if it starts missing after warmed up.

No I haven't fixed the problem yet but don't think I want to pay not knowing whether or not anyone can help me. Thanks anyway.