My wife's 1993 940 automatic has an irregular idle when the engine is started cold. Without any pressure on the accelerator, it tends to idle rather slowly but also surges to 1000-1200 RPM, then quickly drops back in RPM. (At times it almost seems like the tachometer doesn't quite track the actual engine speed). Overall, the idle behavior is rather jumpy/jerky. If I rev the engine for 30 seconds or so, the idle is much more stable afterwards (~700 RPM). The engine rarely stalls, even without revving, but does so very occasionally. Warm starts after the engine has been run for a while are no problem. I have checked the TPS, ECT sensor, and idle air control valve--all are fine. I read out the OBD codes and see nothing indicated (at first readout I did see an indication the ECT sensor/wiring was bad but thought I may have caused this during my diagnostics. I reset the diagnostic unit and see no new codes after many days). I have checked for vacuum leaks and have not found anything thus far. The distributor cap and rotor look quite clean inside. The ignition wires are definitely not new but all read a few K Ohms when I measure them. I am wondering if I may have a bad fuel pressure regulator. Or ????