big BOOM from the exhaust! revs up and down!

My 525 model 90 is having a big problem that happened anytime that the car want to happen. that means that sometimes is going fine and sometimes the revs are going up and down, sometimes the engine switched off, sometimes big BOOM!! (like a gun) from the exhaust. I am feeling that something cut the power suddently like immidiate stop of the fuel OR SOMEONE PUT A BANANA IN THE EXHAUST OUTLEN. Like the car cannot breath! sparks and wire sparks are ok. Do u think that is the fuel pump? do u know the symptoms of a fuel pump that need to be replaced?
Any help will be extremely appreciated!

paschalis-
paschalisg@yahoo.com

Do you mean it's backfiring?

exactly! when I press the accelarator is doing this! I can see also a big FIRE from my mirror when I drive in the night. At this time I have no power, missfiring, revs up and down. sometimes it stops but it comes again after a while

Could be a fuel pressure/delivery problem. Have you got plenty of fuel in the car? Is the pump noisy? You could try a different fuel pressure regulator, see if that's misbehaving. If you're not sure get it checked out by someone competent, or you'll ruin your exhaust & cat (if it's not shot already).

HTH

Shaun

Yes, the fuel pump is quite noisy. is possible to heat a big bee like bbzzzzz. I will try the fuel pressure regulator but as I know this regulator is difficult to be faulty. I 'll check...

OK rule of thumb here applied to racecars is also applicable to our cars...

backfire through intake = carburetion (fuel related)

backfire through exhaust = ignition/electrical

thats it.