1987 JEEP CHEROKEE

Typical onset: 80,000-150,000 mi

Symptoms: hard starting when hot, random stalling at idle, check engine light with intermittent codes, poor cold-start performance

Fix: The Renix coolant temperature sensor (CTS) is the #1 culprit—fails internally and gives false readings. Crankshaft position sensor also common. Both sensors together: 1.5-2 hours labor. If the ECU itself fails (less common but happens), you're hunting junkyard replacements since new units are NLA.

Estimated cost: $200-600

Typical onset: 60,000-100,000 mi

Symptoms: white smoke from exhaust, coolant loss with no visible leaks, overheating under load, milky oil, rough idle and misfires

Fix: The GM 2.8L is a known weak point—thin castings, poor head bolt torque retention, and cooling system inadequacies lead to blown head gaskets and cracked heads. Proper fix requires both heads pulled, resurfaced, new gaskets, and often new head bolts. 12-16 hours labor. Many owners swap to a 4.0L instead of repairing.

Estimated cost: $1,800-3,200

Typical onset: 100,000-150,000 mi

Symptoms: shuddering at highway speeds around 45-55 mph, transmission overheating, delayed engagement into gear when cold

Fix: The AW4 auto is generally bulletproof, but the torque converter clutch solenoid and lockup clutch wear out. Internal transmission work: converter replacement and valve body service. 8-10 hours labor for R&R and rebuild. Fluid and filter changes every 30k miles prevent most issues.

Estimated cost: $1,200-2,000

Symptoms: 4WD won't engage or disengage, hissing sound under hood, soft brake pedal (shares vacuum source), 4WD engagement indicator flashing or inoperative

Fix: Command-Trac and Selec-Trac systems use vacuum actuators and a rats nest of aging rubber lines. Lines crack, the axle disconnect actuator diaphragm tears. Diagnosis: 1 hour. Replacing all vacuum lines and axle actuator: 3-4 hours. Not safety-critical but kills 4WD function.

Estimated cost: $300-600

Typical onset: 90,000-130,000 mi

Symptoms: no-start when hot, engine dies after 20-30 minutes of driving in summer, long crank times, loss of power on hot days

Fix: In-tank fuel pump failures are common, but the real Renix quirk is vapor lock due to poor fuel line routing near exhaust. Pump replacement: 2-3 hours (drop tank). Rerouting fuel lines and adding heat shielding: additional 2 hours. Some owners install an external high-pressure pump as a bandaid.

Estimated cost: $400-800

Typical onset: 180,000-250,000 mi

Symptoms: loud knocking from bottom end, oil pressure dropping below 10 psi at idle when hot, metallic debris in oil filter, vibration at all speeds

Fix: The 4.0L is nearly indestructible, but neglected oil changes or running low on oil will wear main bearings and score the crank. Full rebuild with crank regrind, new bearings, and piston rings: 20-25 hours labor. At this mileage, may be cheaper to swap in a junkyard engine (6-8 hours).

Estimated cost: $3,500-5,500

Typical onset: 100,000-140,000 mi

Symptoms: coolant puddles under vehicle, overheating in traffic or on hills, rusty coolant, heater not producing heat

Fix: Original brass/copper radiators are 35+ years old now—end tanks crack, cores clog with sediment. Radiator replacement: 2-3 hours. While you're in there, replace water pump (add 1 hour), thermostat, and all hoses. Cooling system neglect is what kills these engines, not the engines themselves.

Estimated cost: $500-900