F115tlr iac test?

[Sasquatch88]

I recently purchased a boat with an 08 Yamaha f115tlr that Has an idling issue. I noticed that The iac is not clicking or rattling after the engine is shut off. I pulled it out to clean it and was wondering if there’s a way to test it while it’s out? It seems like it has been pulled out before since the screws were a bit stripped so I’m wondering if I’m tracing someone’s steps and going to end with a bad ecu. I want to make sure that it’s not my ecu that’s been fried or if the iac is in fact sticking. Thanks in advance for any suggestions.

 

[rejesterd]

It might be both. A bad IAC can fry the ECU. You can do the active YDS test if you get the cable and software (look on ebay) If it's working, you'll definitely hear it hiss and the engine will rev up. Otherwise, your best bet is to probably take a temperature gun to it after the engine has run for a while. If it gets over 200F or so, it's probably bad.

But what exactly is the idling issue? Better to rule out other possibilities first. Note that on my 2011 F50, I don't hear it rattle when I shut the engine off, and it appears to be working fine.

 

[Sasquatch88]

Thanks for the response..

your right it could be both. I guess I been under the impression that if I don’t hear it reset at shut down then it is prob not working or given a command and thought maybe there was a way to actuate it with a 12v battery to rule things out.
The engine stalls when you throttle it too fast but it will stay on if you slowly accelerate it. The rpms jump around if you hold it around 2-3k rpms. So far I’ve replaced spark plugs, I’ve cleaned vst tank and replaced screen, changed out fuel filter And flushed injectors. I have yet to check fuel pressure, compression or any air leaks.

 

[rejesterd]

The possibilities I can think of are:

-TPS, IAC, and/or ECU issues
-Damaged throttle body that isn't allowing the valve to open enough
-Faulty ignition coil or spark plug wire
-Damaged diaphragm in the mechanical fuel pump
-Worn/bent VST needle
-Incorrect resistance in one or more injectors
-Damaged pressure regulator

It would probably be well worth getting the YDS kit. You can graph some data points while the issue occurs in real time, and you might get lucky and see an error code that points toward the problem. I and others would be happy to review the data.

To start though, take a look at the VST needle and the fuel pump diaphragm. Those are the easiest things to check. Then maybe remove the intake silencer and get a look at the throttle valves and see how they respond when you throttle up (with the engine not running of course). Then get a spark tester tool just to rule out issues with the coils/ and plug wires. Then get into the electrical stuff with YDS and the service manual (which will give you specs on injector resistance, expected TPS voltage.

 

[Sasquatch88]

Thanks those are some good pointers! I’m going to look into the yds kit. I was going to check the tps but It looks like I need a test harness so I’ll be needing that as well. Thanks I’ll keep you guys updated on the progress