Volvo Repair: 88 244, Hard Warm Start, Runs Rough, coolant temperature sensor, air intake hose

Question
Regis,
I would appreciate your thoughts on these symptoms: 1988 244  USA, 200K+ mi, owned since new.  Starts cold just fine, immediately starts to “hunt” at idle, runs rough (cold or hot), seems to “cut out” just as the accelerator is let off after reaching speed (that momentary point at which the car is neither accelerating nor decelerating), idles poorly and will sometimes stall upon starting out.  Hot start after sitting for short period very difficult; usually only starts by cranking and gradually pressing accelerator to floor.  Evidence of running rich by heavy black soot in tail pipe and a little black smoke visible at idle.  Problem has gradually gotten worse over a year or so.

New catalytic converter, plugs, plug wires, air filter within last 10K mi.  Recently put in new O2 sensor , changed fuel filter and checked timing with strobe (seemed to help a little) and both mechanical and vacuum advance appear to be working.  Vacuum gage shows about 13 inches, jumpy (+/- 1 or 2).  Cleaned spark arrestor, checked extensively for vacuum leak.  Hasn't had ECU adjusted for many years/miles.

Thanks in advance for your help.


Answer
many things can cause this.it will need to be looked at for a proper diagnosis.sounds like possibly a bad engine coolant temperature sensor.other possibility is the air mass meter is bad.if you disconnect the air mass meter the sensor in the air intake hose and it idles better it is probably bad.