I've got a 1987 240 DL Wagon which has low miles and a sweet interior. I just finished going through a lot of restoration work to make it extra nice for my wife. Now it's really nice and has developed a weird problem. Sometimes it drives beautifully, acceleration is good, shifts smoothly (manual tranny). Other times I shift into first and accelerate well until about 10 miles per hour when the power just drops right off. Then I shift into second and it accelerates until 20 miles per hour (or so). So I shift to third and I'm good to 35, fourth to 45 or so. In each gear, I hit a point at which the engine ceases to produce any power; I can put the pedal to the floor at that point and it doesn't get any better.
I ocasionally get a little backfiring as this happens, so I tried removing the flap in the fresh air intake (thinking the flap might be restricting the flow of air and my mixture was going to hell). This seemed to work. I drove it for a few days with no problems. Then the problem reared its ugly head again. I've looked at quite a few things (idle air control, AMM, vacuum lines, and I put in a new coil). If you have any suggestions including specific things to look for in the parts I already checked, I will go back and look at them again. I am stymied. My wife wants to drive her new/old Volvo and is getting perturbed.