I have the most strange of problems with my S90. As a lifelong Volvo owner, I have been able to tackle most all problems encountered. The really fun one was the replacement of the sensor on the distributer plate on my 740 using JB weld and a rivet gun... worked perfectly after that

well...here goes.

for a couple of years my S90 will hestitate and blow black smoke intermittently. It boggs down and then suddenly lurches with a further press on the gas pedal. NOW, HERE IS THE KICKER, It will do this immediately when I fill the Fuel tank. In other words I can induce the problem by simply filling the gas tank.It will start to sputter and spew black smoke right at the gas station. I have hoped that as time went on it would reveal itself as something that actually disables the car. it has not, but it is quite frustrating. the dealer wants $600-1000 dollars to LOOK at it... could be as high as $2000 according to them, but they dont venture a guess (at least not to me)

It will do this for days, or it may go for weeks without a hitch (or immediately on a full tank). No real link to weather, rain or humidity as far as I can tell. Please help?

Well, something similar happened to my 740 turbo. I finally replaced the air filter and that cured the problem. And, no, you couldn't tell by looking at the old filter that it was bad.

You are getting good technical advice from some Brickboard 960 experts in this thread-- let me offer you some practical but non-technical advice-- your dealer is sending you a message that they don't want to work on your car anymore unless it is a sure thing for them that they will make money on the job (the financial risk is yours, not theirs). They are suggesting 6-20 hours of labor! Frankly, you don't want them working on your car anymore either-- dealerships are set up to service new cars and their viability depends partly on their service business.

The more appropriate approach for things that aren't DIY is to find a good independent Volvo-only shop. These shops tend to be owned or staffed by people who cut their teeth in dealerships a decade or more ago who have set off on their own. They probably serviced our cars when they were new and know them well. Some even keep parts cars and can supply you with good used parts where appropriate. There are 5-6 of these guys who are regulars here and their knowledge is impressive. In most cases you'll get better service from one of these independents and you don't have to talk to (or pay for) a "service advisor" in a white lab coat.

Good luck!

Check the line from the carbon canister to the engine and see if it has fuel in it the next time it happens.

DEWFPO
--
1998 S90 083,228 and 1995 964 154,100

Could it be a vacuum line around there that sucks in the fuel, when the fuel level is full?
Tom

My guess (and that's all it is) is it's either in the fuel pressure regulator or the return line to the tank. The bog and smoke means extreme richness in the fuel/air mixture. So that means way too much fuel is getting to the cylinders. The regulator's job is to allow only so much fuel to the injectors. All the rest gets bypassed and sent back to the tank via the return lines. If this problem occurs more when the tank is full, that could mean that something along the return line is blocked and forcing fuel past the fuel regulator.

Now I'm going to sit back and wait for everyone to tell me how wrong I am in 3... 2... 1...

As someone else said, this is the time to go find yourself a good independent mechanic who specializes in Swedish cars. Because, as my old mechanic for my Nissan used to say, "I don't work on Swedish cars. No way in hell. They don't break normal." I think he had a bad experience as a child with a Saab.