1984 PONTIAC BONNEVILLE

Typical onset: 80,000-140,000 mi

Symptoms: Delayed or harsh 1-2 and 2-3 shifts, especially when cold, Slipping under load or complete loss of reverse, Burnt ATF smell and dark/burnt fluid on dipstick, Governor pressure issues causing no upshift or erratic shifting

Fix: Full rebuild required—valve body, clutches, bands, seals, and torque converter inspection. 8-12 labor hours depending on shop efficiency and parts availability. TH200-4R's reputation for weak intermediate band and overdrive clutches makes this nearly inevitable on higher-mileage survivors.

Estimated cost: $1,800-3,200

Symptoms: Hard starting when hot, flooding, or long cranking periods, Rough idle, stalling at stop lights, or high idle that won't drop, Black smoke from tailpipe indicating rich condition, Fuel leaks from accelerator pump seals or float bowl gaskets

Fix: Rebuild kits address most issues—gaskets, diaphragms, needle/seat, accelerator pump. 3-5 hours for experienced carb tech. Many shops now prefer replacing with remanufactured unit due to lack of competent carb rebuilders. Ethanol fuel accelerates internal corrosion and rubber degradation.

Estimated cost: $350-800

Typical onset: 60,000-100,000 mi

Symptoms: Excessive engine movement visible when revving in park, Clunking or thumping when shifting D-to-R or accelerating hard, Vibration through floorboards and steering wheel at idle, Fan shroud contact or hood alignment issues from engine sag

Fix: Replace all mounts simultaneously—engine mounts and transmission mount. Rubber compounds from the '80s are long deteriorated. 2-3 hours total labor. Original-style mounts from aftermarket suppliers are adequate; polyurethane upgrades available but transmit more NVH.

Estimated cost: $250-500

Symptoms: Intermittent stalling when engine is fully warmed up, restarts after cooling, No-start with no spark at plug wires despite cranking, Misfiring or hesitation under load, especially in hot weather, Sudden death while driving with no warning

Fix: HEI module (mounted under distributor cap) is common heat-related failure point. Module replacement is 0.5 hours, but distributor cap, rotor, coil, and pickup coil should be inspected simultaneously. Cheap replacement modules fail frequently—use AC Delco or quality equivalent. Distributor shaft bushings can also wear causing timing instability.

Estimated cost: $150-400

Typical onset: 100,000-150,000 mi

Symptoms: Blue smoke on startup or during deceleration, One or more quarts of oil consumed between 1,000-mile changes, Fouled spark plugs in specific cylinders, usually #2 and #5 on the V6, Loss of compression revealed by cylinder leak-down test

Fix: Rings and possibly valve seals need replacement—requires engine removal or in-car teardown. 18-25 hours labor for proper ring job including cylinder honing, deck resurfacing inspection, and valve work. Many opt for low-mileage junkyard engine swap instead given age and overall condition. High-mileage 231 V6 is notorious for ring land carbon buildup.

Estimated cost: $2,500-4,500

Typical onset: 70,000-120,000 mi

Symptoms: Engine stumbles or dies under acceleration, especially uphill, Hard starting requiring excessive cranking and pumping accelerator, Stalling at idle after extended highway driving, Weak fuel pump pressure (below 5-7 psi for carbureted models)

Fix: Mechanical fuel pump mounted on block is original—diaphragm and valves wear out. 1-2 hours to replace pump, check sock filter in tank, and blow out fuel lines. Many install inline electric pump as upgrade for reliability, though purists avoid this. Varnish buildup in fuel lines from sitting is epidemic on these survivors.

Estimated cost: $200-450