1991 LEXUS LS 400

Typical onset: 100,000-180,000 mi

Symptoms: knocking or ticking from lower end, oil pressure warning light, metal shavings in oil, complete seizure in worst cases

Fix: The 1UZ-FE in 1990-1994 models is extremely intolerant of extended oil change intervals. Sludge blocks oil passages, starves bearings, spins rod or main bearings. Fix requires short block replacement or full rebuild with new pistons, rings, bearings, and often machine work on crank and block. 20-30 labor hours for engine removal, teardown, rebuild, and reinstall.

Estimated cost: $4,500-8,000

Typical onset: 80,000-150,000 mi

Symptoms: ATF leaking near radiator or under transmission, burnt ATF smell, transmission slipping or delayed engagement if fluid level drops

Fix: Steel cooler lines rust through where they connect to the radiator or run along the underbody. Replacement involves dropping parts of exhaust and transmission crossmember for access. Some shops replace just the lines (2-3 hours), others recommend the auxiliary cooler assembly. Flush and refill ATF afterward.

Estimated cost: $400-800

Typical onset: 120,000-200,000 mi

Symptoms: clunk on hard acceleration or deceleration, excessive vibration at idle, visible engine sag when inspected from below

Fix: Hydraulic mounts deteriorate and leak fluid, turning to mush. Transmission mount is the usual culprit but front and rear engine mounts also fail. Each mount takes 1-2 hours to replace depending on access. Budget 4-6 hours if doing all mounts at once.

Estimated cost: $600-1,200

Typical onset: 150,000+ mi

Symptoms: hesitation or stumble under load, difficulty starting when hot, intermittent stalling, fuel pump whine

Fix: The 1991 has an in-tank sock filter on the fuel pump that clogs over time, especially if rusty fuel was ever added. Requires dropping the fuel tank (2-3 hours) to access. Many shops replace the entire pump assembly rather than just the filter since labor is the same and pumps are often weak by this mileage.

Estimated cost: $500-900

Typical onset: 100,000-180,000 mi

Symptoms: no crank when engine is hot, single click or nothing when key turned, starts fine when cold

Fix: Starter is mounted on the valley between cylinder banks and cooks. Solenoid contacts fail or armature shorts. Replacement requires removing intake plenum and various hoses for access. 3-4 hours labor. Rebuild kits exist but most techs replace the unit.

Estimated cost: $600-1,000

Typical onset: 100,000-160,000 mi

Symptoms: whining noise on startup or when turning, fluid leak from pump or high-pressure hose, heavy steering if fluid runs low

Fix: Pump seals fail and high-pressure hose develops seepage at crimps. Pump replacement is 2-3 hours; pressure hose another 1-2 hours if you're addressing both. Some shops rebuild pumps but replacement is more common now.

Estimated cost: $500-900

Typical onset: 120,000-180,000 mi

Symptoms: battery light illuminated, dimming lights, no-start after sitting, voltage below 13V at idle

Fix: Denso alternators are reliable but brushes wear out. Alternator is tucked low on the passenger side; requires removing splash shields and belt. 1.5-2 hours labor. Rebuild is possible but replacement is typical.

Estimated cost: $400-700