Possible idle mixture screw adjustment or vacuum leak
SOURCE: idle is too low, car dies, engine runs fine
An IAC (idle air control) motor is designed to adjust the engine idle RPM speed by opening and closing an air bypass passage inside the throttle body. The car computer or ECM (electronic control module) receives information from various sensors and will output signals to adjust the IAC motor in or out to adjust engine idle speed by controlling engine idle air.
An IAC motor is highly susceptible to carbon and coking build up; if an IAC goes too long without cleaning it can cause stalling and poor idle quality. Some cars are designed with a large vacuum transfer hose that connects the intake manifold to the IAC (idle air control) motor. If a broken or dilapidated these vacuum lines can cause the engine to lose vacuum which will allow the engine to run rough and die.
Inspect all engine and accessory vacuum lines to look for missing, torn or dilapidated lines and replace as needed. To check the IAC motor remove the unit, with the wires connected turn the key to the "on" position without starting the engine, the IAC should move in or out.
If the IAC motor does nothing it has probably failed, replace it with a new unit and recheck system. Note: while the IAC motor is removed clean (use aerosol carburetor cleaner) the passages the IAC uses to control idle air speed.
Good luck and hope this helps
SOURCE: 400 Eiger ATV, starts and runs fine, stalls the
If 2 stroke check crank seals, check plug cap for proper resistance,check for good fuel flow to carb.Spark should jump at least a 1/4" gap,NOT JUST the .030 or plug gap.
SOURCE: engine idles excesivly high after carb was rebuilt.
I sounds like the choke is not adjusted properly or the linkage for the fast idle cam is sticking. The fast idle cam is on the right side (passenger side) of the carb kind of behind the choke assembly. It could be the choke pull-off is not working or is not adjusted properly. Does the choke open all the way when the vehicle is fully warmed up? If not I'm guessing the choke stat (black plastic round) is not working or is installed wrong. Does that one have a wire going to the stat, is there 12V there when engine is running? That gets power direct from the alternator and will only have power there when the engine is running.
SOURCE: i have a husky 455 rancher.never had a problem
When this has happened to me, it turned out to be a hole or crack in the fuel line. At the higher revs, more fuel is needed. The added "suction" for the higher demand pulls air into the line and the unit does not have enough fuel to run. Check for that first and also the fuel filter inside the tank. The filter might be clogged as well.
Keep us posted,
Dan
Testimonial: "got some very usefull stuff off ur reply, i did'nt know u could cx the fuel filter. Turns out my prob was actually a bad batch of fuel, but your reply gave me many options if it happens again in future. thanks for you time."
SOURCE: I have a 2004 honda rancher 400cc and it won't idle.
clean idle jet. If that does not do it. back out fuel mixture screw 1/4 turn
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