1990 INFINITI Q45

Typical onset: 80,000-150,000 mi

Symptoms: Loud ticking or tapping from valve covers, especially cold start, Loss of power and rough idle, Check engine light with misfire codes, Eventually progresses to complete lifter failure and bent valves

Fix: Requires removing both valve covers and camshafts to replace all 32 hydraulic lifters. Quality OEM or Nissan lifters are critical—aftermarket often fail quickly. This is a 12-14 hour job if you're doing it right with proper cam timing verification. If lifters have already damaged valves, you're looking at head removal and valve work adding another 8-10 hours.

Estimated cost: $2,800-4,500

Typical onset: 60,000-90,000 mi intervals

Symptoms: No symptoms until catastrophic failure, Engine suddenly dies and won't restart, If belt breaks: bent valves, damaged pistons, potential complete engine rebuild needed

Fix: This is an interference engine—if the timing belt snaps, valves hit pistons. Preventive timing belt service (belt, tensioner, water pump, seals) is 8-10 hours. If the belt has already failed, you're looking at head removal, valve replacement, and often piston/ring work. Many owners end up with short block replacements or complete rebuilds at $6,000-10,000. Do the belt every 60k religiously.

Estimated cost: $1,200-1,800 preventive / $6,000-10,000 after failure

Typical onset: 100,000-180,000 mi

Symptoms: Pink or red fluid dripping under engine bay, Transmission fluid in coolant reservoir (milky appearance), Transmission overheating or erratic shifting, Low transmission fluid level

Fix: The cooler lines crack at fittings and the internal radiator transmission cooler can fail, causing fluid cross-contamination. Line replacement is straightforward (2-3 hours), but if the radiator tank has failed and ATF mixed with coolant, you need radiator replacement, complete fluid flush of both systems, and sometimes transmission filter service. Total 4-6 hours if doing it all.

Estimated cost: $400-800 lines only / $1,200-1,800 with radiator and flush

Typical onset: 70,000-120,000 mi

Symptoms: Clunking when shifting from Park to Drive or Reverse, Vibration at idle in gear, Excessive driveline movement during acceleration, Visible cracking or fluid leakage from hydraulic mount

Fix: The rear transmission mount is hydraulic-filled and fails commonly. Replacement requires supporting the transmission and unbolting the crossmember—about 2-3 hours. OEM mounts last longer than aftermarket. While you're there, inspect the front engine mounts as they wear similarly.

Estimated cost: $350-600

Typical onset: 120,000+ mi

Symptoms: Extended cranking before engine fires, especially when warm, Rough idle and hesitation after sitting, Fuel smell from engine bay, Loss of fuel pressure after shutdown

Fix: Fuel filter clogs, fuel pressure regulator diaphragms fail, and injector o-rings leak on these aged V8s. Filter replacement is 1 hour. Regulator is another 1.5 hours. If you have leaking injectors, budget 4-6 hours to pull the upper intake plenum and replace all o-rings and seals. In-tank fuel pump can also weaken—that's a 3-4 hour tank-drop job.

Estimated cost: $150-300 filter/regulator / $800-1,400 full injector service / $600-900 fuel pump

Typical onset: 90,000-140,000 mi

Symptoms: Suspension warning light illuminated, Loss of ride height adjustment, Harsh ride or excessive body roll, Hydraulic fluid leaks at struts or actuators

Fix: The 1990 Q45 came with Nissan's Full Active Suspension on some trims—hydraulic actuators, accumulators, and a complex control system. When components fail, replacement parts are scarce and expensive. Many owners convert to conventional coilovers (8-10 hours labor for full conversion). OEM repair of individual struts runs 4-6 hours per corner if parts are available.

Estimated cost: $1,500-2,500 per strut OEM / $2,000-3,500 full coilover conversion

Typical onset: 100,000-150,000 mi

Symptoms: Battery warning light, Dimming headlights or interior lights, Dead battery after short trips, Voltage gauge reading low (below 13.5V)

Fix: The alternator is tucked low on the passenger side and requires removing the lower splash shield and working from underneath. Not terrible but tight access makes it a 2-3 hour job. Test the battery and connections first—these cars have multiple ground points that corrode and mimic alternator failure.

Estimated cost: $450-700