'77 320i Stutter/Sputter - NEWBIE NEEDS HELP!

[gfulcher]

Greetings! I'm not new to vintage german cars - but I am to ones with a radiators and fore-mounted powerplants! Actually, my friend just purchased a near-cherry '77 320i (E21) with 85k or so original miles, driven by the wife of a Bimmer mechanic. Anyhow, the original owner sold the car to my coworker, who sold it to my friend - basically, just passed the car along. We brought the car to my garage where it sits until the following problem is solved.

The only thing apprarently wrong mechanically is in regards to a stutter/sputter/bog/lack of power - but only after the engine reaches operating temperature. Runs GREAT up until this point - it happens every time without fail. (which I think is a good thing as it can be replicated).

Once the stuttering starts, all we have to do is turn the car off momentarily, fire it back up and viola! no problems - runs like it did while cold - but only for a minute or less and then it all starts over again.

Also, the engine has trouble getting much past 4800 RPM when the problem occurs - when 'cold', it goes to redline rapidly. Fuel consumption seems excessive, too - yet there is no smoke in the exhaust.

Engine has new points/condensor: Dwell is adjusted to factory specs. Timing is adjusted to spec at 2400rpm. Car has a new cap/rotor/wires & plugs. Fuel pump is pushing out the proper pressure and the vacuum readings average 15 - 18. Haven't yet performed a compression check.

My logic is that this is a temp-related problem, perhaps with a sensor, sending unit or valve being controlled by the aforementioned. Could it be as simple as a relay?

We're awaiting arrival of a Haynes manual tomorrow, but I"m eager to hear any suggestions! I'm not yet up to speed with all the parts' names and locations - but hope to be after a few more hours under the hood.

Thanks in advance!

-greg-