Hey all,
So my 1994 940 n/a has been having idling problems lately. Symptoms are slight shake, sputter, dip in rpms (400 back to 700 back t0 400…) only in gear at stop lights and when coming to a stop. Once I get up to 1100 rpm or so I can feel him get back to normal. When i put it in park, idles normal at 700 or so. Car has 257,000 miles, owned since 200,000 and has always ran super smooth. Another small, but possibly related issue is that my cruise control has been losing vacuum lately? The following has already been done:

cleaned IAC and throttle body: 215,000 mi
timing belt-212,000 mi
fuel pump: 200,000 mi
fuel filter: 220,000 mi
spark plugs: 250,000 mi

I know its not a super comprehensive list, but he's never given me problems. I've only replaced items with Volvo/OEM parts as well. Any ideas? Could spark plug wires or cap and rotor cause these issues? The odd standout symptom to me is that it only does it at idle in gear and not in park.

Thanks guys!