2005 F225 problem

[hnewstreet]

I have a 2005 Yamaha f225 4-stroke that runs rough between 900 and 1,400 RPM in gear. The engine will show an air intake passage fault (#37). When we disconnect the shift position switch, the engine will act up and fault code #37 will show. By acting up I mean the RPM becomes unstable and the IAC % drops from 30% to 0% and will never return to normal operating duty cycle %. The IAC valve is operating and does attempt to stabilize the engine RPM when the problem occurs. We know this because we took the IAC off and watched it move.

So, the question is, what the heck is wrong with my engine? Why would it only act up between 800 and 1,400 RPM and in gear? Why is fault code #37 showing? I have attached a scan of the printout from the diagnostic report. My mechanic doesn't think it is the IAC and I am not real excited to buy a $450 part on a guess. Could it be the computer (a $1,000 part)? Bottom line is that I don't want to guess and keep buying expensive parts on a whim.

Thanks in advance for any help.

[fairdeal]

well, you've come to the right place. If you are going to get a useful answer, it will be here, from the two most experienced, best informed Yamaha experts on the internet (i won't name them so as not to hurt the others' feelings)

While you wait for them to read your post - perhaps you could clarify:

you say "When we disconnect the shift position switch, the engine will act up and fault code #37 will show"

Do you also get a code 37 with the shift position switch connected?

[hnewstreet]

yes, we get the code when the position switch is connected. The reason we disconnected the switch was to make sure it wasn't the switch causing the error.

[boscoe99]

[hnewstreet]

Should we go through this even though it idles fine? The only time it acts up is in gear and the throttle has been slightly increased to 800 RPM and then stops once it goes past 1400 RPM.

[fairdeal]

"Incorrect Idle speed control signal"

I can't imagine what Yamaha means by that;

it can't mean the ECM is "seeing an incorrect signal from the ISC"

because it doesn't GET any signal FROM the ISC



I have pain between my ears.....

[rodbolt17]

couple of thangs a going on.
1st is why isn't your certified master tech using YDIS version 2.2?

second is why is the TPS value so out of spec?

the MEDS lists the wrong TPS value.

like its been pointed out, the ISC is NOT monitored by the ECU for ANY failures.
the % reading is simply an ECU request and has nothing to do with did it move,

also you don't "test" a switch by simply unplugging it.

does your tech have ANY Yamaha training certificates on the wall ??
code 37 wasn't used by Yamaha on that year motor.
MEDS may see it but its wrong.
that's also why I use YDIS 2.2 and not MEDS.
typically the intake air pressure code is set by a back fire in the intake.

[Nautical]

Has anybody done any work on the motor prior to the problem?ie intake manifold ?etc

[boscoe99]

Is it not strange that a 2006 Yamaha F225 did not use code #37 but the Yamaha 2003 F225TXRC service manual makes reference to code #37?

Is this just another Yamaha data screw up?

[hnewstreet]

Ok, here is more of the back-story and answers to some of your questions. I bought the boat (a 22' Edgewater) and motor last year. Before I even used the boat once I had it serviced by a Yamaha certified mechanic and he said everything was OK and that the inner exhaust looked OK. On our maiden voyage, after one hour of use, it started acting up. I restarted the engine and the problem went away. The next trip it did it after an hour of use again. After that trip I called the Yamaha mechanic, explained the problem and he agreed to check it out again. He told me that the engine was showing a code but that he wasn't sure what was causing it and he didn't want to guess. He didn't tell me the code or give me the report and suggested I call someone else.

I have lived with the problem since then. However, it has gotten worse over time. Now it happens every time I am at that specific RPM range (900 - 1400). So, I took the boat to a friend of mine that is a certified Evinrude mechanic and asked him to run a report, and hopefully provide enough information that I could post it to this forum and look for help.

So, what would you recommend?

Thanks!!!!

[hnewstreet]

I am not real interested in going back to that Yamaha mechanic after he told me to "find someone else". I also don't want to buy diagnostic tools for my mechanic. I was really hoping to get some answers here. I live in South Florida, so there are plenty of Yamaha mechanics. I just want to be able to have it fixed the first time and not randomly replace parts on a guess.

Thanks

[boscoe99]

You got a code #37 being set which according to Yamaha relates to an idle speed issue.

You got an idle speed issue by your own admission.

You got a graph which shows the idle speed varying even though the throttle position is fixed.

You got a graph showing the intake manifold pressure is varying even though the throttle is not opening and closing. And presumably the idle air control valve is fixed not allowing more or less air into the intake manifold.

You got a Yamaha chart indicating to check the intake manifold for leaks if the idle speed is not steady.

Does any of this sound like an intake manifold vacuum (air pressure really) leak?

[chummy70]

I'd say yes on leak.

[fairdeal]

You got a graph showing the intake manifold pressure is varying even though the throttle is not opening and closing...

Does any of this sound like an intake manifold vacuum (air pressure really) leak?

perhaps that varying intake manifold pressure value is erroneous?

how about a leak in the hosing connecting TO the MAP sensor -

there's a spiderweb of little tubing behind the port side throttle bodies

if I was looking for a vacuum leak on an 11 year old engine,

rubber tubing would be an obvious start

of course there's some rubber hose on the ISC, too....

[rodbolt17]

I am sure someplace near you has a competent tech.
the TPS values are way off.
some circuits actually share the same 5V reference.
lose the correct ref voltage and guess what the ECU see's for a sensors return voltage?