misfire on 1993 Lexus SC400

my car messed up out of no where, when i took it to the shop they say my car has a misfire. the machine that they are using to tell where the misfire is coming from has not told them anything, my car idles really funny and shaky, my rpm line is bouncing between the 123 and getting stuck and the car is smoking out the pipes black smoke, i can drive the car but it rides really bad and it will not accelerate over 30 mph....

by in Sacramento, CA on March 25, 2010
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2 answers
ANSWER by , March 27, 2010
Bad news is all I have i am guessing you have a tremendous amout of miles on this car. You probably have a cracked ring or a Valve guide seal leaking. hopefully only a valve guide seal leaking. Buy a couple cans of SEA FOAM engine Treatment and pour one Can per Tank of Gas and see if this helps. Good Luck
ANSWER by , September 10, 2010
probably the fuel pressure regulator or improper vacuum going to it.