Re: e36 wont start at times help!!!
Occasional low power may mean battery is about to die, or battery cable not attached securely (was probably disconnected during heater core job).
Cranking with no start means check for both spark and fuel pressure. Hard to narrow down better than that here on-line.
Whining when you press the gas: Check the rubber elbow from the MAF sensor to the throttle body. Chances are it is split where the finger-sized tube is inserted on the outboard side. If the elbow is OK, then go on to check for any other vacuum leaks typical of E36s at this age.
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