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munkymush
10-27-2009, 06:42 AM
does anyone know where i can get info on the air idle valve fitted to a 350mcx yr 2004
i would like to know if the valve is adjustable for stroke length? ive read that some are on other auto engines,, ive just had mine out for cleaning as i have a tickover issue with it.
is there any books or info thats available to purchase with in depth info on these engnes?

JimN
10-27-2009, 10:18 AM
does anyone know where i can get info on the air idle valve fitted to a 350mcx yr 2004
i would like to know if the valve is adjustable for stroke length? ive read that some are on other auto engines,, ive just had mine out for cleaning as i have a tickover issue with it.
is there any books or info thats available to purchase with in depth info on these engnes?

Why did you remove it for cleaning? What is "tickover"?

It's adjustable but not by the user. The dealer should have a diagnostic computer and that has a way to "repark" the IAC (Idle Air Control). If the key was turned on while it was out, don't just push the tip back in.

munkymush
10-27-2009, 10:26 AM
tickover is idle.. there is loads of info on air idle valve on the internet.. even where they power them up and move them in +out .. what makes the mastercraft one so special that it cant have the same done to it ,surely the ecu reparks it next time its switched on + off ?

JimN
10-27-2009, 10:43 AM
tickover is idle.. there is loads of info on air idle valve on the internet.. even where they power them up and move them in +out .. what makes the mastercraft one so special that it cant have the same done to it ,surely the ecu reparks it next time its switched on + off ?

It can be cycled manually but it doesn't tell the ECM where it is, so it can remain out of position even if the controller tells it to close when its position has been changed through other means.

It's not an MC part but the controller/program Indmar uses determines what can be done and how. The marine software isn't exactly the same as auto, although some crossover does exist. "Repark" means "close pintle and open xx steps", not "close pintle and leave it there", so you may end up having more idle issues after you adjust it.

What issues does it have? Too high/low idle speed? Hunting for the correct RPM? Not smooth?

coz
10-27-2009, 11:02 AM
GM 5.7 Litre 350

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 cars 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 can fail one of two ways, either the motor short circuits and stops working or the motor will develop high resistance and cause the IAC control motor to react slowly, either failure can cause the engine to stall at idle. When a trouble code scan is performed it sometimes won't always detect a failed or weak IAC motor. 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, also inspect the IAC for a build-up on the seating (pointed) end and clean as necessary.



Common Problems

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. Any car that is designed with a magnetic non-motor operated IAC like Toyota/Lexus is subject to carbon and should be cleaned about every 40,000 miles to avoid stalling.

Basic Maintenance

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, also inspect the IAC for a build-up on the seating (pointed) end and clean as necessary.

http://www.2carpros.com/how_does_it_work/images/iac_idle_air_control_motor.jpg

$100 new from NAPA auto parts, just had to replace mine.

munkymush
10-27-2009, 11:44 AM
mine is hunting at idle.. and seems to either be better at 500rpm or it goes ok at approx 1000rpm.. wasnt to sure wether to suspect either the tps or air idle valve ..its not a cheap part in the uk .. either 150 or 260 depending on which type apparantly.. im just checking alternative sources,, i cant believe they are any thing more than an auto unit ..?

coz
10-27-2009, 11:58 AM
i cant believe they are any thing more than an auto unit ..?


It's a GM truck engine that Indmar tweeks for marine use and alot of parts are available at the auto parts store. It's probably $999.99 if you get it through MC :D

JimN
10-27-2009, 04:20 PM
It's probably $999.99 if you get it through MC :D

He posted, on the FREE forum MC provides for users of their boats.

So, buy it from a Bu or Supra/Moomba dealer if you don't like the price.:rolleyes:

JimN
10-27-2009, 04:23 PM
mine is hunting at idle.. and seems to either be better at 500rpm or it goes ok at approx 1000rpm.. wasnt to sure wether to suspect either the tps or air idle valve ..its not a cheap part in the uk .. either 150 or 260 depending on which type apparantly.. im just checking alternative sources,, i cant believe they are any thing more than an auto unit ..?

How old is your PCV valve? Have you checked spark, and vacuum? If it hunts up AND down, it's most likely a symptom, not the cause. I don't think I replaced one on any of the boats I worked on, with the possible exception of maybe one at MC training. If yours is the stubby version, it could have different issues but it was always something else that made it hunt.

What is available there for cleaning fuel systems? Try that first.