Engine idles too high sometimes 04 SSV

[msutoad]

I have an 04 Launch SSV with the Assult Indmar engine. Sometimes the motor seems to idle high like at 1500 RPM, which is about 900 RPM too much. If I disengage the prop and rev the engine, it will drop down to normal, or if I turn the motor off and back on it will be normal. It does not do it all the time, and it is not just when the motor is cold or hot. The timing varies. Any idea what the cause of this might be? I know the motor is computer controlled, so I am a bit unsure.

Many thanks

[DKJBama92Mariah]

Im thinking a sticking idle air control valve.

Does anyone else have an idea? anyone...... Bueller...... Bueller.


DKJ

[msutoad]

What is that, and where is it? Is it a dealer only fix, or can it be done be me at home? My boat is still under warranty, but the dealer is 162 miles from home .

Thanks alot.

[DKJBama92Mariah]

Sorry, its taken so long to reply. I went to the beach for the weekend and ended up sitting on my butt waiting out tropical storm arlene.

I hate to say it, but i see a long tow in your future. Since your boat is still under warranty, I couldnt with a clear conscious advise your to just start throwing parts at the boat based one my speculation.

I'm not sure exactly the layout of your motor since mine is a good old fashioned carb motor, but i'll give it a shot at describing it.

The idle air control valve (also known as a stepper motor in some applications, mostly british) regulates the amount of air entering the intake manfold when the engine is at idle and the throttle butterfly in the throttle body is completely closed. On a carb, this was accomplished by the idle stop screw which holds the primary butterflies open a little but. In an EFI motor, the idle air control valve (IAC valve) provides a bypass around the throttle butterfly for air to flow when the engine is at idle. The engine computer (ECM) uses the IAC valve and its control of the injectors to maintain idle speed. If this valve sticks, it will allow too much air into the motor, and hence, a abnormally high idle speed.

As far as where to find it, here goes. The IAC should be a device screwed into the intake plenum close to the throttle body. It will have probably 2 or 3 wires attached to it. The part screwed into the plenum will probably be about 3/4" to 1" in diameter.

Thats about all i can tell you. The only experience i've had with these was on my land rover defender. The IAC's (british term stepper motor) are notorious on these motors for getting gummed up, and sticking, causing the same symptoms you describe. I've found on my rover, that simpy pulling the valve and giving it a good cleaning with carb cleaner usually solves the problem.

Nonetheless, i would still advise just taking it to the dealer and letting them fool with it. I'm not sure how warranty work is handled, but you may not have to take it to a Supra dealer for the motor work. If i understand correctly, the engine is warranted through Indmar, not Supra, so an Indmar dealer should be able to process the warranty claim for you. This might help if there is an indmar dealer closer to you than your Supra dealer. You can search for Indmar dealers on their website www.indmar.com

Hope this helps.

Cheers,
DKJ

[KenG]

Msutoad,

I know a little about GM MEFI (version 3, which is probably older than what you have but the basics are the same). There are a few easy checks you can do yourself.

1) Make sure your throttle valve is returning fully to the stop when you return your throttle lever back to the neutral/idle position. The throttle valve stop should be fully against the stop on the throttle body at idle. If not, you could have a weak spring on the throttle valve, a binding throttle cable, etc.

2) The ECM actually uses both the IAC valve and the ignition timing to control the idle speed. If you have the jumpers to put the ECM in service-mode and an inductive timing light, check the base timing. I think 10° BTDC is normal for the GM 350 with EFI.

3) To test the IAC valve:
a) With the engine at normal operating temperature, note the engine RPM at idle.

b) Stop the engine and disconnect the IAC wiring connector at the IAC valve.

c) Restart your engine and note the engine RPM. The engine speed should be a couple hundred RPM higher with the IAC valve wiring disconnected.

d) With the engine still idling, re-attach the wiring connector to the IAC valve. The engine speed should decrease close to the original RPM noted in step a.

e) If the engine speed varied as described in steps c & d, the IAC valve is probably OK.

f) If the engine speed did not vary, then, using a 12-volt test light, with the engine running and the wiring harness disconnected from the IAC valve, test each of the four terminals in the IAC valve wiring harness. The test light should blink when connected to each one. If so, the IAC valve is probably defective. If one or more terminals do not cause the test light to blink, there may a damaged wire in the wiring harness, a poor connection at the ECM or a faulty ECM.

4) Inspect the distributor cap and rotor. The aluminum contacts inside the cap can get very corroded.

Good Luck.

--KG--

[Brian Raymond]

Do you have a Digital Pro or Wakeboard Pro installed on your boat? Brian Raymond

[msutoad]

I have Wakeboard Pro Brian. Does that matter?

Thanks to all that have replied!

Jason

[msutoad]

Brian-

Does the model of Perfect Pass matter for the idle irregularity I am referring too?

Thanks for your help.

Jason

[DKJBama92Mariah]

Toad,

To check and see if your PP is causing the problem, just unhook the PP servo cable from your throttle arm and spend a day at the lake riding the old fashioned way. If possible, i would disconnect the power to the PP when doing this so the electronics don't freak out on you.

Cheers,
DKJ

[msutoad]

Thanks for the info. I have spoken to Indmar, and they think it is the IAC valve as others have mentioned. I have it going to someone Monday to get looked at under warranty . I will post the findings here when they are done with it.

Thanks

Jason