Owning an HA3/HA4 Honda Acty—like many Japanese Kei trucks—is often more about maintenance than repair, but because many of these vehicles are 25+ years old when they arrive abroad, specific patterns of failure have emerged.

The most critical thing to know is that the Acty has an interference engine. If the timing belt snaps, the pistons will hit the valves, effectively causing serious damage.  

Here are the common problems categorized by system:

1. Engine & Cooling System (Critical)

The HA3/HA4 Acty engine (E07A) is generally strong and robust but is also sensitive to heat and neglect.

• Overheating: This is the main killer of Acty engines. The cooling system lines are long (running from the front radiator to the mid-engine), making them prone to air pockets.

  • Symptoms: Temperature gauge spikes, overflow tank boiling over

  • Cause: Old coolant, failed thermostat, or air bubbles in the system (bleeding the system can be difficult and requires raising the front of the truck).

• Timing Belt Failure: As mentioned, the E07A is an interference engine. If the timing belt breaks, the pistons will hit the valves.

  Recommendation: Unless you have documented proof it was changed recently, replace the timing belt, water pump, idler, and tensioner immediately upon purchase.  They are reasonably priced parts, and once replaced will give you peace of mind for at least 5 years.

• Idle Issues / Hunting:

  • Symptoms: The engine revs up and down at idle or stalls when stopping.

  • Cause: Usually dirty carburetor jets, old vacuum lines that have cracked, or failing solenoids on the carburetor.

2. Transmission & Drivetrain

• CV Axle Noise:

  • Symptoms: Clicking or popping noise when turning.

  • Cause: The CV boots tear due to age, letting grease out and dirt in. This is very common on lifted trucks as the angle puts stress on the joints.

• Clutch Slip:

  • Symptoms: Under harder acceleration the engine revs, but the vehicle does not speed up

  • Cause: Clutch discs wear out over time, and the clutch kit will need to be replaced.  Don't forget to machine the flywheel at the same time.

3. Electrical System

• Ignition Control Module (ICM) / Igniter:

  • Symptoms: The truck cranks but won't start, or it dies suddenly while driving and won't restart until it cools down.

  • Cause: The igniter and distributor components wear out. This is a very common "mystery" stall issue.

• Fuel Pump Relay:

  • Symptoms: Intermittent starting issues; you don't hear the fuel pump "hum" when you turn the key to the ON position.

  • Fix: Often requires replacing the main fuel relay (located under the dash) 

4. Body & Rust

• Battery Box Rust:

  • The battery is exposed to the elements (hung on the side of the frame). The battery tray often rusts out completely.

• Cab Corner & Bed Rust:

  • Check the corners of the cab and the bed hinges. Since these were work trucks in Japan, the beds are often banged up, leading to surface rust that can deepen.

Summary of "The Big Three"

If you are looking to buy or just bought an Acty, these are the three preventative items you should budget for immediately:

1. Timing Belt & Water Pump (Critical engine protection)

2. Cooling System Flush (Prevents overheating)

3. Carburetor Solenoid & Igniter Replacement (Ensures a smooth idle)

If you need any help with critical mantenance parts for your Honda Acty be sure to contact us and we will be happy to assist!