The 1991 Toyota MR2 with a 5S engine model is known to suffer from oil leaks, particularly around the valve cover gasket and oil pan due to worn gaskets and seals.

This model can experience overheating issues often due to a failing radiator, water pump, or thermostat. The cooling system components may be prone to wear and tear over time.

The 5S engine is susceptible to head gasket failures which can lead to coolant leaks, engine overheating, and loss of compression.

The timing belt in the 1991 MR2's 5S engine needs regular replacement, as failure can result in severe engine damage.

Issues with the electronic fuel injection system can arise, such as faulty sensors or clogged fuel injectors, leading to poor fuel economy and engine performance.

Problems with the ignition components, such as the distributor cap, rotor, spark plugs, and ignition wires, can cause misfires, rough idling, and starting problems.

The 1991 Toyota MR2 with a 5S engine model is known to suffer from oil leaks, particularly around the valve cover gasket and oil pan due to worn gaskets and seals.

This model can experience overheating issues often due to a failing radiator, water pump, or thermostat. The cooling system components may be prone to wear and tear over time.

The 5S engine is susceptible to head gasket failures which can lead to coolant leaks, engine overheating, and loss of compression.

The timing belt in the 1991 MR2's 5S engine needs regular replacement, as failure can result in severe engine damage.

Issues with the electronic fuel injection system can arise, such as faulty sensors or clogged fuel injectors, leading to poor fuel economy and engine performance.

Problems with the ignition components, such as the distributor cap, rotor, spark plugs, and ignition wires, can cause misfires, rough idling, and starting problems.

The 5S engine in the 1991 Toyota Celica may experience overheating issues due to age-related wear and tear on the cooling system, such as a failing radiator or water pump.

Common in older engines, oil leaks can occur due to degraded seals and gaskets, particularly around the valve cover, oil pan, and crankshaft seals.

The 5S engine uses a timing belt, which can wear out over time and require replacement to prevent catastrophic engine damage.

With electronic fuel injection, issues such as clogged or malfunctioning fuel injectors can cause poor engine performance and reduced fuel efficiency.

A known issue in older 4-cylinder engines, head gasket failure can lead to coolant mixing with oil, causing engine overheating and severe damage if not addressed.

Problems with spark plugs, ignition wires, or the distributor can lead to misfires, rough idling, and difficulty starting the engine.

Vacuum hoses and fittings can deteriorate over time, leading to vacuum leaks that result in poor engine performance and erratic idling.

The Exhaust Gas Recirculation (EGR) valve can become clogged or fail, leading to increased emissions and potential engine performance issues.