1. Diagnose the Problem:
* Movement Issues: Does the seat not recline, slide forward/backward, or adjust height properly? Is it completely stuck? This often points to mechanical issues like broken cables, worn tracks, or seized mechanisms.
* Comfort Issues: Is the seat uncomfortable due to worn foam, torn upholstery, or broken springs? This is usually a reupholstery or foam replacement job.
* Loose Seat: Does the entire seat feel loose or unstable? This might be due to loose bolts connecting the seat to the floor or broken seat mounts.
2. Common Fixes and Troubleshooting:
* Reclining Issues: The recliner mechanism uses a cable and lever system. You'll need to access the mechanism (usually under the seat) to inspect the cable for breakage or fraying. You might need to replace the cable or lubricate the moving parts. A repair manual will be invaluable here.
* Sliding Issues: The sliding mechanism uses tracks and rollers. These can get clogged with dirt, debris, or become worn. Cleaning the tracks and lubricating them might suffice. Worn rollers or tracks often require replacement.
* Height Adjustment Issues (if equipped): This is often a hydraulic or pneumatic system. Leaks or a broken pump can cause failure. These usually require replacement of the entire height adjustment mechanism.
* Loose Seat: Check all the bolts that attach the seat to the floor. Tighten them, but don't overtighten. If the mounts themselves are broken, you might need to repair or replace them – a challenging job.
* Upholstery and Foam Repair: For tears or worn upholstery, you'll likely need to reupholster the seat, either yourself (difficult and requires skill) or by a professional. Replacing the foam padding is also possible but requires removing the upholstery.
* Broken Springs: This usually requires professional upholstery work to replace the broken springs.
3. Tools and Resources You'll Need:
* Repair Manual: A 1990 Buick Park Avenue repair manual (available online or from auto parts stores) is absolutely essential. It will show you diagrams and procedures for accessing and repairing the seat mechanisms.
* Socket Set and Wrenches: For removing and tightening bolts.
* Screwdrivers: Phillips and flathead.
* Pliers: For working with cables and other small parts.
* WD-40 or Similar Lubricant: For cleaning and lubricating moving parts.
* Shop Towels or Rags: For cleaning.
* New Parts (if needed): You'll likely need to source replacement parts from a junkyard, online parts retailers (like eBay or RockAuto), or a Buick parts specialist.
4. Safety First:
* Disconnect the Battery: Before working on any car electrical system, disconnect the negative battery terminal to prevent accidental short circuits.
* Use Safety Glasses and Gloves: To protect yourself from sharp edges, debris, and potential injury.
In short: Without knowing the *specific* problem, it's impossible to give precise instructions. Start by carefully inspecting the seat and identifying the fault. Then, consult a repair manual for your 1990 Buick Park Avenue to find the appropriate repair procedure. If you're not comfortable working on cars, it's best to take it to a mechanic.
