Troubleshooting a Rough Idle on the Honda Acty: Carb vs EFI Fixes

A rough idle in your Honda Acty can be frustrating, especially when the engine shakes, stalls, or surges unpredictably. The solution often depends on whether your Acty is carbureted (like the HA3/HA4 with the E05A engine) or fuel-injected (like the HA6/HA7 with the E07Z engine). On carbureted models, common causes include dirty or clogged idle jets, vacuum leaks from cracked hoses or intake gaskets, misadjusted air/fuel mixture screws, or a worn distributor cap and rotor. Cleaning the carburetor, checking vacuum lines, and setting the idle screw to spec often restores a smooth idle. In EFI models, the issue may stem from a dirty idle air control valve (IACV), a faulty MAP sensor, leaking intake manifold gaskets, or fuel delivery problems like clogged injectors or a weak fuel pump. Both systems can suffer from basic tune-up issues like old spark plugs, failing ignition coils, or incorrect valve lash. Diagnosing rough idle in an Acty means starting with the basics—air, fuel, spark, and vacuum—and then narrowing down based on whether you’re dealing with a carb or EFI setup. With the right approach, even stubborn idle issues can usually be solved without major engine work.