Intake Air Control Valve?

[fedpo]

2004 200hp Mercury (200XL) with carbs (serial # 0T922318)

I just read a post on here where someone with similar problem I'm having fixed his problem by cleaning the IAC (Intake Air Valve). I'm trying to determine if my engine (listed above) has this part. I see a Thermal Air Valve listed, but I don't know if this is the same part as the IAC. Any and all help would be GREATLY appreciated! I've been dealing with this problem for a LONG time now (either a fuel flow issue or a loss of power to a cylinder once the motor warms up for a mile or 2). VERY FRUSTRATED!

 

[Chris1956]

Re: Intake Air Control Valve?

The thermal valve allows more air into the motor when it is cold. This extra air raises the idle. After the motor warms up, the thermal valve closes, restoring the slow idle. Is that the issue?

You might give us a blow by blow description of the issue.

 

[fedpo]

Re: Intake Air Control Valve?

Thanks for the info Chris. My issue is the motor starts great, idles normally and runs as it should while it's cold (good pick-up out of "the hole" and cruises at 5000 rpms and 40-45 mph). After several minutes, the motor "jumps" a couple times, then it loses power to 4000 rpms and 35-40 mph. I've replaced plugs and cleaned the carburators. I may have some kind of fuel flow blockage between the primer ball and the gas tank. If I disconnect the fuel line and pump fuel from a different tank, the primer bulb feels "normal." When I pump fuel from the main tank, the primer bulb does not feel like it pumps much gas. If I prime the ball NUMEROUS times, it will eventually feel normal. I'm hoping to have time today to access the main gas tank to see if there is something blocking the intake. When the motor "jumps", however, it feels more like an electrial issue than a fuel flow issue. Often times, when it's not running normally, when I power down from 4000 rpms to idle, the motor will cut off. It always starts right back up without a problem and idles normally again. When I attempt to accelorate, there is not much pick-up. It will slowly get back up to 4000 rpms. HELP!

 

[Faztbullet]

Re: Intake Air Control Valve?

The thermal valve allows more air into the motor when it is cold. This extra air raises the idle. After the motor warms up, the thermal valve closes, restoring the slow idle. Is that the issue?

Your engine does not have a IAC valve ,only 4 strokes. You have a thermal valve and below is how it works. Your problem sound more like a bad/failing CDM module and your loosing a cylinder.

The thermal air valve restricts the air for the idle circuit by thermally opening/closing valve via engine temp. When the engine is below 100? the air valve is closed. When closed(cold) the air valve restricts air to the idle circuit causing the fuel mixture to be richer. When the engine warms the valve opens allowing outside air to idle circuit like a normal carb. This is one thing you check if idiling rich as I have cleaned dozens of dirt dauber plug from the open enf of valve.