Why after it did the tune up on my buick rendezbouz it starter misin up

Check out this video, should cover it:
How To GM 3800 V6 3 8L Starter replacement

Clean your fuse block by hand carefully or replace it. Corrosion is not always visible.

QUESTION: Without a jump, does the motor crank when you turn the key to "START"?

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If you can jump start it, then you know you have spark, fuel and compression; you know your starter and ignition are fine.

My guess is a loose/missing connection at the positive battery terminal for your starter.

When you tightened the battery connection you may have twisted the cable on the starter and shorted it to the solonoid lead causing the starter to engage . Check the connections on the starter and make sure there are not touching each other. Hope this helps.

did you check the code,check starter.fuel filter.

This car is over 30 years ???Any codes?Battery and connection, tune up, fuel filter, dirty throttle body, air filter???

When was last healthy tune up? I would change plugs, wires, all filters including FUEL filter then run a good fuel system cleaner through it like STP or Gumout. This will give you a good "ground zero" point for reliability.

Nope, click is solenoid on starter not fully engaging....either new battery (see if changes when on a jump start) or new starter motor

The starter and solenoid are underneath the exhaust manifold on the passenger side. You need to raise the vehicle and remove this assembly from below. There are two large bolts which secure the starter to the engine block. There may or may not be shims placed between the starter and the block. DON'T LOSE THOSE SHIMS! There is also a bracket with a stud and nut that supports the front end of the starter. There may also be a heat shield to protect the starter from the hot exhaust manifold. DO NOT THROW THE HEAT SHIELD AWAY. If you do, your new starter won't last 6 months. The heat will destroy it. Once the starter is loose, lower it by hand. You will now have access to remove the two wires from the solenoid. These can be tricky to remove. If in doubt, have a professional do it.
To install, reassemble in reverse order.
Charlie

have the computer checked.it sounds like it may be getting weak or going bad.