My '89 240 wagon with 160K on it is OK until it warms up, and then it begins to kinda limp and will not accelerate. It just back fires, then might die. Or it might continue to idle and I can coax it along by pumping the accelerator like mad.
I've developed a check list to trouble shoot with:
Vacuum leaks – check all hoses.
Check housing around air box and AMM
Throttle Body Switch
Leaks around intake manifold
Air Intake to Throttle Body
Fuel Injectors/Seals
O2 sensor (don’t know when last replaced, but looks like it might be the original one).
Fuel pump... Hose to the Tank test.
Replace fuel pump relay (recently resoldered the one in there now).
Radio Suppression Relay.
Faulty IAC (I cleaned this, but perhaps not well enough).
Temp sensor

Bear in mind the rotor, cap, wires, plugs, FPR, and fuel filter are new already.
Would you add anything to this checklist? Many thanks in advance.