4G93 Engine

Introduction

The engine designated 4G93 is part of the legendary evolution of Mitsubishi’s “Sirius” and “Saturn” families, but specifically belongs to the 4G9 series. The variant we’re talking about today is the DOHC (Double Overhead Camshaft) version with 16 valves and natural aspiration, producing 140 horsepower. It’s best known for being fitted in the Mitsubishi Colt IV (CAO) GTi, a car that in the 1990s was a serious rival to models such as the Honda CRX or VW Golf GTI.

This engine comes from the golden era of Japanese engineering – built to rev high, last long with proper maintenance, and deliver a raw driving experience without too many electronic aids.

Technical Specifications

Reliability and Maintenance

Timing belt or chain?

This engine uses a timing belt to drive the camshafts. It’s very important to note that, although it’s a Japanese engine, skipping belt replacement intervals is not an option. The recommendation is to do a major service every 60,000 to 90,000 km or every 5 years, whichever comes first. When replacing the belt, you must also replace the tensioners, idler pulleys and water pump.

Most common failures

Although robust, the 4G93 in this configuration has a few characteristic weak points:

• Hydraulic valve lifters: This is “classic” for Mitsubishi engines from that period. The symptom is loud ticking/rattling from the top of the engine, especially on cold start. If the noise doesn’t disappear once the engine warms up, the lifters need to be replaced or cleaned. Using high-quality oil reduces this problem.
• Idle control (Stepper motor/IACV): The idle air control valve often gets dirty or fails, which leads to unstable idle, stalling at traffic lights or fluctuating revs. Cleaning often helps, but sometimes replacement is necessary.
• Oil consumption (Valve stem seals): Due to the age of these cars, the valve stem seals harden. This manifests as bluish smoke from the exhaust on first start or after idling for a longer period.
• Ignition distributor electrics: Spark plug wires and distributor cap are wear items, but if they’re in bad condition, the engine will misfire and lose power.

Oil: Capacity and grade

The engine takes approximately 3.8 to 4.2 liters of oil (depending on filter and oil pan size). The manufacturer originally recommended grades such as 10W-40 or 5W-40. For normal climate conditions and considering the mileage of these vehicles, 10W-40 semi-synthetic is the most common and usually the best choice. Change it every 10,000 km at most, or once a year.

Oil consumption: On older examples, consumption of up to 0.5 liters per 1,000 km is tolerated if driven aggressively. If it exceeds 1 liter, it’s time for an engine refresh (piston rings and valve stem seals).

Specific Parts (Costs)

Dual-mass flywheel and clutch

Good news: This engine DOES NOT have a dual-mass flywheel. It uses a conventional solid flywheel, which significantly reduces maintenance costs. A clutch kit (pressure plate, disc, release bearing) is relatively affordable – it falls into the “not expensive” category.

Injection system and injectors

It uses a classic MPI (Multi-Point Injection) system. The injectors are electromagnetic, very simple and rarely cause trouble. They are not as sensitive to poor-quality fuel as modern GDI injectors. Ultrasonic cleaning solves most issues with uneven running.

Turbo, DPF, EGR

This engine is naturally aspirated, so there is no turbocharger. Also, given the age and the fact that it’s a petrol engine, it does not have a DPF filter. An EGR valve in the modern sense (that clogs and causes chaos) is not a problematic component here. The system is mechanically simple, which is a big advantage nowadays.

Fuel Consumption and Performance

City and highway driving

Don’t expect miracles in terms of fuel economy. This is a GTi engine.

• City driving: Realistically expect between 10 and 12 l/100 km. If you have a heavy right foot, it can go even higher.
• Country roads: With calm driving (up to 90 km/h), you can get it down to around 7–7.5 l/100 km.
• Motorway: At 130 km/h the engine is spinning at quite high revs (close to 4000 rpm in fifth gear), so consumption is around 8–9 l/100 km. It’s not the quietest companion on long trips.

Is the engine “lazy”?

Absolutely not. With 140 hp in a Mitsubishi Colt weighing around 1000–1100 kg, this car is very agile. The engine loves to rev – it delivers power linearly, but the real fun starts above 4000 rpm. Throttle response is instant.

Additional Options and Modifications

LPG conversion

Yes, this engine is an excellent candidate for LPG. Thanks to indirect (MPI) injection, installing a sequential LPG system is straightforward and doesn’t require expensive hardware. However, since this is a Japanese engine with mechanically adjusted valves (or hydraulic lifters that can be sensitive), it’s recommended to install a valve lubrication system (“valve saver”) or to strictly adhere to regular ignition system maintenance.

Remapping (Stage 1)

Since this is a naturally aspirated engine, remapping doesn’t make much sense. The gain would be negligible (maybe 3–5 hp), which you won’t feel in real driving. It’s better to invest the money in a quality exhaust system, a cold air intake and, above all, in bringing the engine back to proper factory condition (full service).

Gearbox

Manual gearbox

It most commonly comes with a 5-speed manual gearbox (F5M22 series or similar). These gearboxes are precise and have a sporty feel. The most common issue is with the synchros for second and third gear. If the gearbox grinds when shifting quickly from first to second at high revs, the synchros are worn.

It’s recommended to change the gearbox oil every 60,000 km (75W-90 GL-4).

Automatic gearbox

There is also a version with a 4-speed automatic. Honestly – avoid it in the GTi model. It’s an old-style torque-converter automatic that is slow, chokes the engine’s performance and increases fuel consumption by 1–2 liters. Its reliability is decent if the oil is changed regularly (every 40–50,000 km), but it kills the sporty character of this engine.

Used Car Buying Guide and Conclusion

What to check before buying?

1. Cold start: Listen to the engine while it’s cold. If you hear loud metallic knocking that doesn’t go away after 10–15 seconds, the hydraulic lifters need replacing or the oil pressure is poor.
2. Exhaust smoke: Rev the engine once it’s warm. Blue smoke = burning oil. Black smoke = poor combustion (mixture issue). White smoke (when the engine is hot) = head gasket problem.
3. Corrosion: The 90s Mitsubishi Colt has serious rust issues. Be sure to check the wheel arches, sills and underbody. A good engine is pointless if there’s nothing solid to bolt it to.
4. Timing belt: Ask the owner when it was last changed. If there’s no proof, factor in the cost of a full timing service immediately.

Conclusion

The Mitsubishi 4G93 (140 hp) is a gem from the past. It’s aimed at enthusiasts who want a cheap, fast and mechanically simple hot hatch. It’s not for someone looking for comfort, quietness and low fuel consumption. If you find an example whose body hasn’t been eaten away by rust, the engine will, with regular oil and belt changes, serve you surprisingly long and provide a lot of fun.