'89 volvo s70

My father in law just gave us a '98 Volvo S70 and it has broken down 3 times in 3 months. We figured it was classic fuel pump issues, but after the second and third time, we can’t figure out what is going on. Before it breaks down, it starts mad-idling, the rpm guage flies all over the place, and it’s always when the car is at a standstill and usually when the car is angled at least slightly uphill. What’s going on?! We’ve sunk tons of money into this b/c of it and it doesn’t seem to be getting any better. While it’s running, there is still lots of idling at stop lights and signs. The car has had all of it’s major tune-ups, changes, etc. 175K miles. Any ideas anyone?

Stop putting money into that thing. It would be a good car if anybody could fix it. It sounds like nobody can. You can’t predict the future all the time, but I see a different one running in yours.

Some information would help; maybe.
Any Check Engine Light coming on?
Exactly what has been replaced?
You assumed the fuel pump. Has the pump been replaced?

Next, I would advise dropping by a local AutoZone and have them pull any codes. They will do this for you free. Post any results back here for further discussion.

Since you have a wildly fluctuating tachometer, this often points to a problem in the secondary ignition; usually the distributor or ignition module, etc.

There are some other possibilities, but getting the codes read and providing some more info is next.