Its been about 3 years since I've owned a Volvo, but I have one now, and its the 4th one I've owned. I've never come across this problem before.
The vehicle always starts good, but was missing horribly and bucking under any type of acceleration when warm. When the car was fully warmed, and I kept pumping it to keep it alive, it would all of the sudden take off. Then it wouldn't miss a beat until it was shut off again. I replaced the dist. cap and rotor, and that didn't help much.

Any ideas?? I really don't think it is fuel related as you can smell the unburned fuel from the exhaust. And there are no stored trouble codes.

It is a 1990, there are no trouble codes, it has a half a tank of gas in it, and I did check the air mass meter it is fine, I just recently replaced the spark plugs.

Replaced the crank position sensor yet?
For information, look in the 740/940 FAQ. Under engine sensors, the left side dropdown menu.

Truth be told, it usually causes occasional no-start and then complete no-start. Not famous for rough running followed by no start. But you do need to check it; most of the original crank position sensors have bit the dust by now.

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Sven: '89 245 NA, 951 ECU, expanded air dam, forward belly pan reaches oem belly pan, airbox heater upgraded, E-fan, 205/65-15 at 50 psi, IPD sways, no a/c-p/s belt, E-Codes, amber front corner reflectors, aero front face, quad horns, tach, small clock.

What year car? We need to know.

Also this very rough running could be caused by a failed air mass meter.
Test for this:
With ignition off, and preferably the key in your pocket,
Disconnect the cable to the air mass meter (amm).
AMM is located mid way in the fat accordion hose from air filter housing to the throttle body.
With AMM disconnected try start the engine. If it idles better with amm disconnected then you need a new amm. Best bet usually is used out of a junker. That's a much better value than reconditioned or new, generally.

Again, be CERTAIN the ignition is off before you reconnect the amm.

Get back to us with the year and how the amm test went.
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Sven: '89 245 NA, 951 ECU, expanded air dam, forward belly pan reaches oem belly pan, airbox heater upgraded, E-fan, 205/65-15 at 50 psi, IPD sways, no a/c-p/s belt, E-Codes, amber front corner reflectors, aero front face, quad horns, tach, small clock.

How full is the fuel tank if it is low I wonder if the secondary pump is running the changing sound from the main fuel pump is definitely not normal. Fill the tank right up and tell us if that makes it better.
Regards,
Checkpoint Charlie

D, its been three years since you owned a Volvo, but what model year is the car? Is the car still exhibiting the symptoms?

Look at the ignition coil wiring system for any loose connections.

I did take some steel wool and clean up all the connections on the coil. I also did the same with all the fuses and put all new fuses in. The main fuel pump does make a funny sound sometimes. It will sound normal (low buzzing noise) for about 5-6 seconds, then make a gushing/gargling noise, then go back to running good for the 5-6 seconds,...so on and so forth. Is that somewhat normal??


Also, the car currently runs so bad it is not drivable. It just stumbles/bucks/and misses so bad you have to pump it constantly just to keep it alive.

That is good that you cleaned the connections up at the ignition coil. The connections and those nuts can sometimes loosen up and cause problems.

You need to pull out a spark plug and have either an assistant crank the motor over or use a remote starting switch with the fuel pump relay disconnected. Ground plug to the block and check to see if the spark is regular and of good quality.

I think though that your problem lies in the fuel system. The fuel hose for the tank pump can deteriorate and cause problems. Fill the tank above 3/4 and see if the problem still exists. You can though check the quality of the fuel system another way. Look at the photos below and there you will see how I made a port to check the pressure of my fuel system in my 264 - B23F conversion. Also see my post about Red Lobster:

http://www.brickboard.com/RWD/index.htm?id=1239230

After fabricating the port checking the pressure will reveal faults that are otherwise difficult to diagnose.

Another way to check the system is to use the fuel hose method. Put a propane source connected to a hose into the inlet for the airbox. If the situation improves then the fault is certainly in the fuel system. You can also use starting fluid or a gas soaked rag.

Good Luck!!!