Classic/Antique Car Repair: 88 CHEVY CAPRICE CLASSIC 305 ROUGH RUN, 1988 Chevrolet Ignition

Question
HAVE 88 CAPRICE CLASSIC WITH 305/8 THAT IS MISSING TERRIBLY. HEARD CLICKING NOISE FROM UNDER HOOD, LOOKED AND SAW COIL WIRE SPARKING TERRIBLY. ALSO, FUEL TANK HOLDS MASSIVE PRESSURE,WHEN TAKING OFF FUEL CAP. TONS OF PRESSURE EVEN WHEN VEHICLE HAS FULL TANK. TANK WILL EVEN FLEX ON MANY OCCASSSIONS WHILE RUNNING OR SITTING. RUNS MUCH WORSE WHEN VEHICLE GETS WARM OR HOT. AT WITS END, PLEASE HELP

Answer
Hello David,

The symptoms you describe point to bad wiring between the coil and the spark plugs, including the distributor cap. Your car has a High Energy Ignition system which runs at about 40K volts. With this much voltage, wiring with insulation break down will arc as you describe. Get what's called an Ignition Wiring Set from a quality source like NAPA. Replacing the wires is easy if you're careful to match lengths with the old, replace one at a time and numerically label the ones you're taking off as well as it's position on the distributor cap. If you're not familiar with cylinder numbering, it is 1-3-5-7 on the left side as determined from the drivers seat and 2-4-6-8 on the right side.

Fixing problems like this is like peeling back an onion---there can be multiple causes to a problem. As noted, start with wiring replacement, if that doesn't work, check, clean and/or replace the distributor cap if it shows cracks or corrosion. Finally, check and or replace the spark plugs, again with quality replacements like AC which originally came with the car.

Regarding your fuel tank, modern cars like yours have a closed system for emissions controls reasons. This means they're non-vented to the outside and can build up significant pressure. As fuel tanks are mostly made from plastic, they will harmlessly distort under pressure. There are hoses and an an absorbent filter designed to trap the vapors. Check for kinks in the lines and a damaged or missing filter. With the fuel vapor recovery system working properly, you can reduce this problem but unfortunately can't eliminate it as its part of the price for clean air!

I think the rough running may be coincidental to the tank issues. Fix the wires and see what happens.

Good luck,

Bob