1990 Chrysler Le Baron Check Engine Light Stays On Car Drives Very Rocky

Then check engine light stays on and the car drives very "rocky". The mechanic said it needs a tune up and
a new fuel injector. The new fuel injector was installed but does not "throw" and fuel when it is used in the
bad slot. If he swaps it and puts it into the working slots, it does "throw" fuel. He put a new fuel hose in and
and put the new fuel injector back to the bad slot and it still doesn't "throw" fuel. The car is undriveable. What
is the problem?
Thank you for your help