A minor but persistent (year-long) rough idle on my 1991 240 has quickly turned into a Cold Start Nightmare over the past month:

SITTING HOURS OVERNIGHT (70-degree temp overnight) - When I attempt to start in the morning, the engine idles high for 3-5 seconds and then immediately dies. To successfully start, I must keep pressing the accelerator pedal at least half-way down for 2-3 minutes. The engine sputters, almost backfires, shakes, lopes, almost dies, etc. After 2-3 minutes, everything runs just fine. If I shift into [Drive] or [Reverse], and press the accelerator and brake at the same time, the idle is just a bit smoother, but I can slowly pull off within 45 seconds instead of 2 minutes.

AMM UNPLUGGED IN THE MORNING - the engine will start OK (slightly rough, but does not die)

SITTING HOURS IN THE DAYTIME (95-degrees outside) - If I try to crank during lunchtime (4-hrs later) or after work (8-hrs later), the vehicle idles roughly for a few second but does not die.

WARM ENGINE SITTING FOR A FEW MINUTES - Once the engine is warmed up, it will consistently start withouth problems. Still a slightly rough idle, but OK. The car does not die.

BATTERY DISCONNECTED BRIEFLY - If I disconnect the battery for 2-3 minutes, reconnect and try to start, the terrible rough idle returns! Engine sputters, almost backfires, and I must hold the accelerator for 2-3 minutes before it will idle on its own. This happens even if the engine is completely hot!

Over the past 3 weeks, I have checked/changed every vacuum line; had the local volvo mechanic check my throttle body / TPS switch; swapped out the Idle Air Control motor; checked/changed the distributor cap, rotor, and spark plug wires. Then LH 2.4 Check Engine codes are "2-2-1" and "2-3-2" (lean or rich mixture). My local volvo guy says it is probably NOT the AMM, but he is so backed working on air conditioning systems and other emergencies that it will be next weekend before I can leave my car for him to examine in depth.

Why does disconnecting the battery trigger the cold start symptoms? Is the ECU bad? Any suggestions would be appreciated.

The wife had to drive the Volvo last week, and now she insists that I say goodbye to Sweden get another Nissan. (My other car, her daily driver, is a 2001 Nissan Altima.)

Southern Fried Volvo, 1991 volvo 240, frayed and frazzled at 215k mi