DIY - Replacing Idle Air Control valve (IAC) or Throttle Position Sensor (TPS)

[formulaben]

Here is a quick tutorial for those who have never changed either of these. It is very easy so long as you have a (#??) torx driver for the 2 screws that secure each one and that is it. The hardest part is making sure you don't drop the retaining screws into the bilge. This swap was done on a 2002 Wakesetter LSV. YMMV.

First step is to remove spark arrestor and decorative plate below it.

Next, remove weather pack connector plug for either TPS or IAC.  Here are plugs removed from both sensors:

Here, the gray sensor is the new TPS:

Reinstall connector for whichever sensor you replaced, then reinstall spark arrestor/air filter and you're done. I applied some CorrosionX into each connector.

[Pistol Pete]

Are the mounting holes for the TPS slotted?

I wonder if you have to set / adjust the TPS voltage?

[formulaben]

No, unlike others (I hear) it was pretty straightforward, 2 holes and no adjustment. I was told the ECU "learns" it when it boots up?

[justgary]

I think so. It's pretty easy for it to get the idle value when you turn the key on, and it probably assumes some number for WOT until it learns otherwise.

It may not be such a bad idea to disconnect the battery for a while to "unlearn" the ECM, then reconnect it and teach it the throttle range with the key on/engine off. Just moving the throttle from idle to wide open a few times should do it. Maybe this is completely unnecessary, but I don't think it will hurt anything.

The IAC is just a stepper motor with a plunger, and it should train itself at every startup also by fully closing until it stalls when you first turn the key on.

[WheelerWake]

I think so. It's pretty easy for it to get the idle value when you turn the key on, and it probably assumes some number for WOT until it learns otherwise.

It may not be such a bad idea to disconnect the battery for a while to "unlearn" the ECM, then reconnect it and teach it the throttle range with the key on/engine off. Just moving the throttle from idle to wide open a few times should do it. Maybe this is completely unnecessary, but I don't think it will hurt anything.

The IAC is just a stepper motor with a plunger, and it should train itself at every startup also by fully closing until it stalls when you first turn the key on.

I believe you are supposed to put the controller in "service mode" after replacing the IAC.

[electricjohn]

I thought you had to preset the pintle length before installing the IAC.

[malibu2004]

I replace both of mine 4 or 5 years ago. I didn't do anything other than remove/replace and start the boat.

[Fman]

Just for my learning purposes, what were the symptoms to require a iac replacement? Rough idle?

[WheelerWake]

Just for my learning purposes, what were the symptoms to require a iac replacement? Rough idle?

The IAC controls the rpm at idle, so too high or too low...

[justgary]

The IAC controls the rpm at idle, so too high or too low...

Or stalling, or too rich, too lean, hard starting...

[dtm8119]

FYI - The Clymer manual I have states the following on page 411...

Step 13 (after installing the iac):
Start the engine, then put the engine into service mode. Take the engine out of service mode after operating at idle speed for a few minutes. Operating the engine in service mode calibrates the iac position to the ecu setting. Improper calibration can cause hard starting (particularly when cold), too fast or slow idle speed or stalling when returned to idle position.

[malibu2004]

FYI - The Clymer manual I have states the following on page 411...

Step 13 (after installing the iac):

Start the engine, then put the engine into service mode. Take the engine out of service mode after operating at idle speed for a few minutes. Operating the engine in service mode calibrates the iac position to the ecu setting. Improper calibration can cause hard starting (particularly when cold), too fast or slow idle speed or stalling when returned to idle position.

Can I ask how you put the motor into service mode? I would like to learn so I can do it on mine.

[dtm8119]

Can I ask how you put the motor into service mode? I would like to learn so I can do it on mine.

One of these will do it:

http://www.michiganmotorz.com/codemate-tester-mefi-code-reader-p-2459.html?gclid=COH4u9KL_LsCFY1FMgodPwMAxA

[WheelerWake]

Can I ask how you put the motor into service mode? I would like to learn so I can do it on mine.

You can put it in service mode by shorting pins "A" and "B" together on the data link connector.

[Levi900RR]

Digging this old one up... I get a very intermittent stall / surge when I return my boat to idle. Typically when I'm maneuvering around the dock. Slipping it in and out of gear. Thinking about giving the IAC replacement a shot. Any other ideas?

[Pistol Pete]

That's the first thing I would replace.

[tvano]

Digging this old one up... I get a very intermittent stall / surge when I return my boat to idle. Typically when I'm maneuvering around the dock. Slipping it in and out of gear. Thinking about giving the IAC replacement a shot. Any other ideas?

bakes is asking north of $200 for iac.

auto parts stores are getting > $70.

if it were mine i'd start w the throttle position sensor for half that much.

give a shot at cleaning the iac, too

just spray it w carb cleaner but insure the pintile is down to avoid solvent in the electrical connections.

[eyekode]

Or use MAF sensor cleaner. And don't move the plunger by hand.

[formulaben]

bakes is asking north of $200 for iac.

auto parts stores are getting > $70.

if it were mine i'd start w the throttle position sensor for half that much.

give a shot at cleaning the iac, too

just spray it w carb cleaner but insure the pintile is down to avoid solvent in the electrical connections.

I got my IAC for $37 and the TPS for $41 at the local O'Reilley's...

[justgary]

Also clean the whole inside of the throttle body with spray cleaner, including the butterfly (open the throttle to get the cleaner all around). Gummy passages can cause funny things to happen.

If the engine idle slowly lowers as the engine warms up, the IAC is probably OK.

[Levi900RR]

Awesome info guys. I'll probably give my local parts store a shot as well as cleaning the TB. I've been meaning to get some TB and MAS cleaner for my truck anyway...

[justgary]

So does it do it if you are idling in gear, and then shift to neutral? If so, I think you may have a shift interrupter switch that needs adjustment. Try shifting slowly in and out of gear, and then quickly in and out of gear (stay at idle both ways). Is it different? Just a thought....

[formulaben]

So does it do it if you are idling in gear, and then shift to neutral? If so, I think you may have a shift interrupter switch that needs adjustment. Try shifting slowly in and out of gear, and then quickly in and out of gear (stay at idle both ways). Is it different? Just a thought....

What be this "shift interrupter switch" you speak of? Please expound.

[justgary]

In poking through the MEFI 3 manual, I saw a reference to an interrupter. I don't know if Indmar uses it, but presumably it will kill RPM momentarily as you switch to neutral to allow the gears to unmesh easily. When going into gear, it can be used as a load predictor to juice the idle up just a touch in anticipation of the coming load.

So mostly just thinking out loud, but it occurred to me that my buddy's '03 Response will drop RPM as you take it out of gear. Sometimes it is worse than others, and I think it may be worse if you drag the throttle slowly back to neutral. My '99 doesn't really do it very much at all, so I thought maybe it's an '03 thing.

[Levi900RR]

All good info. I can't put my finger on the EXACT scenario that will always trigger the behavior but typically if I start the boat and just let it idle it runs perfect. If I back it off the lift, like just click it in reverse and back into neutral, then click it in forward to putt over to the dock and I'm going back and fourth from forward to neutral to reverse is when it usually happens. BUT... some days is doesn't. I mean I could go weeks between incidents. And when it happens, I just leave it in neutral, let it find itself and then go on with my day. Maybe twice a year it'll stall and I'll have to restart and all with be well.

Its more of an annoyance than anything else, but it would be cool to make it go away. Plus is makes my OCD meter hit the pin.