I have a 1986 760 turbo wagon. On cold startup the idle is rough and lumpy; after driving 5 or 6 miles the idle smooths out somewhat. After the engine is warm, if the car is left to idle in park for any length of time the RPM will jump from the usual 1000 to 1500 without any reason. It occured to me that the temp sensor may be the problem; does that seen plausible.
Cheers...George
Have you replaced the engine wiring harness yet? Those are notorious for crumbling insulation and will cause all sorts of weird problems.
The wiring harness has not been replaced; you're right the electronics are dodgy. However the rough idle and RPM swing are very consistent suggesting a more concrete problem.
Replace or rebuild the engine harness first, trust me, get that out of the way, the car will never be reliable until it's been done. I procrastinated on mine and ended up rebuilding it on the street in the front of my house on a cold wet January evening.
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