This is probably one for the "best" of you mechanics out there, because there might be too many variables.

I have a 1994 850 Turbo, which is my winter driver here in Chicago. Probably somewhere in the 250,000 mile range, as the odo stopped 6 years ago at 171k. I use the car on nasty salt days, for very short trips, or when my dog needs to go somewhere.

Start with some background:

The car starts fine, and idles fine when warm, but is a bit "rough" until the engine gets some heat.

If I am driving and holding low rpm's while in "D", the car surges, usually about 3 times, and then "settles in" without much further issue.

If I drop the transmission into 3rd, obviously with the higher rpm's there is very little of this.

If I am at higher speeds, 50+ mph, no problem with surging even in "D".

Here is the tricky part that is becoming a problem.

If I stomp on the throttle, or even try to accelerate quickly from low rpm's, the car DOES NOT accelerate. In fact, if feels more like the engine is dying.

The tach needle will rise, but the car will not be accelerating. And I do not believe it is transmission slip, because although the tach needle is showing about 3,700rpm's (almost always exactly this number?!), the engine is not revving. The engine actually is making very little noise, as if it is "choking" or starving. I believe the tach needle movement is electrical related, since the engine is not revving, so I think it is just getting a confused electrical signal?

If at higher rpm's and I accelerate normally, things are mostly normal. But again, even at 50mph, if you STOMP on the gas it just sits there, making no rev's, and the tach needle hangs out at 3,700rpm's.

It does not clear up until you let go of the gas, and then go back to gently feeding the throttle in.

I am looking to know if this is just a hose or line that has come undone on some sort of accelerator pump, or if somebody has been here before and sorted it?

Otherwise, after many good years of service this just might be where my until now trusty winter driver and I part ways.

Thanks in advance to anyone who might be able to shed some light on this!