1. Home
  2. Knowledge Base
  3. Aisan
  4. Troubleshooting (Aisan)
  5. Engine Will Not Idle or Perform Well at Low Speed (Aisan)

Engine Will Not Idle or Perform Well at Low Speed (Aisan)

Possible causes are below, these are the most common possabilities

  • slow jet clogged
  • slow jet not seated properly in main body (if overtightened it will bottom out and if loose it will alter fuel flow)
  • carbruetor to intake manifold nuts loose (ensure lock washers are installed)
  • intake manifold to cylinder head mounting nuts loose

Other possible causes

  • idle screw not adjusted properly
  • idle mixture screw not adjusted properly or tapered end worn or damaged
  • slow port (idle mixture adjusting screw port) clogged
  • primary or secondary throttle shaft worn
  • primary or secondary throttle valve misaligned in bore
  • idle circuit air bleeds clogged
  • incorrect choke plate position (should allow choke to open freely when engine is warm)
  • carburetor thermostatic valve not seating properly
  • retard vacuum pipe loose in flange or leaking
  • economizer jet passage clogged
  • air horn gasket damaged and allowing air to leak into power valve vacuum passage which causes the power valve to open
  • secondary throttle valve not closing tightly

Could be caused by the Thermostatic Valve equipped on some vehicles.

Aisan Carburetor Thermostatic Valve

As the valve opens, it allows outside air to flow directly into the intake manifold, leaning out the rich air fuel mixture. Valve starts to open when engine compartment temperature reaches 140 F, or 60 C and fully opens at 167 F, 75C.

Updated on 04/27/2022

Was this article helpful?

Related Articles

Need Support?
Can't find the answer you're looking for?
Contact Support