I have had my otherwise wonderful red 240 DL sedan in the shop for over week getting looked at with a stumble under load. The car runs fine once you get into higher rpm's, and it idles fine, but apply some load and it stumbles until it revs pretty high.
I've replaced the following items: rotor, cap, plugs, plug wires, fuel filter, air filter, swapped out AMM's and ECU's. I've replaced timing belt and tensioner as well. None of these things have corrected my stumble. What could it be? The car has been otherwise well maintained, oil changes every 3-5k since new, service records, everything. It just keeps stumbling. There is plenty of fuel pressure as well at the line, so my mechanic tells me as he has the tools for this. So FPR is not the issue. Any ideas are greatly appreciated. I have myself and a 25+ year Volvo mechanic stumped!