Engine Misfires on 1990 Chevrolet Lumina

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Problem with the 1990 Chevrolet Lumina Base 6 Cyl 3.1L (88,000 miles)
June 3, New spark Plugs installed. (Original Spark Plug wires remain) July 15, Power Brake Booster Replaced. Shop said battery was disconnected and computer needed to automatically reboot. But the engine stalled all day at stops and when coasting.
July 19, Shop ?cleaned? idle control valve and stalling problem stops. But the Engine now misfires.
August 9, Shop tests (and dislocates coolant reservoir, now rubber bushings are cracked/split) and decides #5 is misfire but they are not responsible. When the engine is cool, it runs steady but as engine heats up, misfire starts. Shop # 2 says New Spark Plug wires must be installed and Induction Service required.
Considering all the problems that GM created with the W-cars...AND these added factors: the serp belt is worn out, the motor mount bushing is split/cracked, the front windshield needs replacing...should I even consider keeping this car? But then why scrap a car with 88,000 miles that can get 32 mpg ?

(1) Answer
Your last question is one that truly only you can answer -- always a tough deal for everyone in the same boat. Knowing when to say when is difficult. I've had people spend $15,000 in the course of a few years making repairs to an aging car. And this was 10 years ago. The only advice I would share is: everything you mentioned is relatively minor. We're not talking engine mechanical failures, transmission failures or anything adding up to huge dollars. So, if the main expensive parts are fine, then perhaps it wouldn't be the worst thing to make modest invenstments when necessary.

Spark plug wires should be replaced when replacing plugs for the first time at such a high mileage. When you disturb the fitment over the plugs, the boots typically crack as they are aged and under stress. When you put them back on, they may arc and be less efficient, causing a performance issue.

The fuel induction service...probably won't improve anything you are experiencing, but is a good idea for continued maintenance.