The 1998 Q45 features Infiniti's sophisticated VH41DE V8 and a complex 4-speed automatic. While luxurious and smooth when healthy, this generation suffers from catastrophic engine failures and transmission cooling system weaknesses that can total the car if ignored.
Camshaft Position Sensor Failure Leading to Valve Timing Issues and Engine Damage
Common · high severityTypical onset: 80,000-140,000 mi
Symptoms: rough idle or no-start condition, Check Engine light with P0340 or P0335 codes, engine misfires under load, catastrophic internal damage if sensors fail while driving at highway speed
Fix: Replace cam position sensors (both banks) preemptively. If internal damage occurred from sensor failure causing timing chaos, expect full teardown. Short block replacement common outcome: 18-25 hours labor.
Estimated cost: $400-800 for sensors alone, $6,500-9,500 for short block replacement with machine work
Piston Ring Land Failure and Cylinder Scoring
Occasional · high severityTypical onset: 100,000-160,000 mi
Symptoms: excessive oil consumption (quart every 500-800 miles), blue smoke on startup and acceleration, loss of compression in one or more cylinders, metallic rattling from engine bay
Fix: VH41DE engines have weak ring lands on pistons; carbon buildup and detonation crack them. Requires full rebuild with upgraded pistons or short block. Engine out, 22-30 hours labor plus machine shop time.
Estimated cost: $7,000-11,000 for complete rebuild; $5,000-7,500 for used engine swap
Transmission Oil Cooler Line Failure and Contamination
Common · high severityTypical onset: 90,000-130,000 mi
Symptoms: transmission slipping or delayed engagement, milky pink fluid in radiator or transmission pan, overheating transmission, complete transmission failure after coolant mixes with ATF
Fix: Steel cooler lines rust internally; radiator internal cooler fails, causing coolant/ATF cross-contamination. Requires new radiator, external cooler installation, full transmission flush or rebuild if contaminated. 8-14 hours if transmission survives, 18-24 if rebuild needed.
Estimated cost: $1,200-2,000 preventive (radiator, lines, external cooler); $3,500-5,500 if transmission rebuild required
Alternator Failure with Voltage Regulator Issues
Common · medium severityTypical onset: 70,000-120,000 mi
Symptoms: battery light illuminated, dimming headlights or interior lights, electrical accessories acting erratically, no-start condition or stalling while driving
Fix: OEM alternators have weak internal voltage regulators; overcharging damages battery and electronics. Replace with quality reman unit, not cheap aftermarket. 2.5-3.5 hours labor (tight engine bay).
Estimated cost: $550-850
Transmission Mount Collapse
Common · medium severityTypical onset: 80,000-140,000 mi
Symptoms: heavy clunk when shifting from park to drive or reverse, vibration through chassis at idle, transmission moving visibly under acceleration, difficulty shifting smoothly
Fix: Hydraulic transmission mount fails from age and heat. Easy access but quality replacements scarce—OEM expensive, aftermarket don't last. 1.5-2 hours labor.
Estimated cost: $350-600
Head Gasket Failure from Overheating
Occasional · high severityTypical onset: 110,000-180,000 mi
Symptoms: white smoke from exhaust, coolant loss with no visible leaks, overheating under load, milky oil on dipstick or oil cap, rough idle with misfire codes
Fix: Usually secondary to cooling system neglect or rad/trans cooler failure. Both heads must come off on V8. Decking required if warped. 16-22 hours labor plus machine work. Often find other issues once heads are off.
Estimated cost: $3,500-5,500
Fuel Filter Clogging and Fuel Pump Wear
Occasional · medium severityTypical onset: 100,000+ mi
Symptoms: hesitation or stumbling under acceleration, difficult cold starts, loss of power at highway speeds, fuel pump whining audible from rear seat area
Fix: In-tank filter clogs; external filter rarely serviced. Pump works harder, fails prematurely. Drop tank for both. 3-4 hours labor. Do both at once—cheap insurance.
Estimated cost: $650-950
Only buy if you're handy, have deep pockets, or get it cheap enough that a $7k engine rebuild is already factored in—most survivors are on borrowed time.
AI-assisted summary drawn from NHTSA recall data, our labor-times database, and platform knowledge. Not a substitute for a pre-purchase inspection on a specific vehicle.