Idle air control (IAC) valve problem??

**Last Dollar** · 10-06-2012, 05:53 PM

I believe I have the dreaded IAC Idle Air Control valve problem on my 03 5.0 MPI Alpha. It will not stay running at idle, dies immediately after it fires. If I advance the throttle some it will start and run but then die immediately when I return the throttle to shift gears.

Just prior to this happening I was cruising along, engine running fine, and then all of a sudden I get the warning tone.....two beeps every 60 seconds. This lasted for several minutes until I came back to the ramp, then when pulling the throttle to enter a no wake zone the engine died. It would only run with the throttle advanced, I was unable to get it into gear as it died immediately at idle. From what I have read on the Internet this is a very common problem on the 5.0 MPI. Anyone experienced this?? Are there other weak areas on this engine I need to know about......spare parts to carry etc????

**JimT** · 10-07-2012, 06:09 AM

IAC failure is very common but an easy 10 minute DIY job. Make sure to replace the filter. I had both IACs fail within a week earlier this year and had one go bad on my prior boat. I now always carry a spare.

**Dave S** · 10-07-2012, 06:56 AM

Those are all signs of a bad IAC.

But before you replace it, remove the IAC filter first and try to start the motor. If it starts and idles then the filter is the problem. If the symptoms still remain, then it is the IAC and it will have to be replaced.

Dave

**scoflaw** · 10-07-2012, 08:39 AM

Don't forget that you can buy the part at NAPA for less than half the $

**ZZ13** · 10-07-2012, 11:38 AM

I keep two spare IAC/gasket/filter combos on my boat (along with two spare impellers and two spare thermostats). The IAC is such an easy swap out that its great peace of mind having the spares. Plus, things mostly break that you don't have spares for so you'll probably go a long time between failures if you keep the spares onboard. Just the way it works.

**jason78** · 10-07-2012, 12:39 PM

Reference Post #8 in this thread for details. http://clubsearay.com/showthread.php/36072-Impeller-IAC

**Last Dollar** · 10-18-2012, 10:05 AM

Just replaced the Idle Air Control on my boat and it took care of my problem. Now I will carry a spare next season for sure. A 10 minute repair and all you need is an allen wrench!! Very common problem on MPI engines from what I have learned from my Internet searches.
Carry a spare!!!

**psubill78** · 10-18-2012, 09:45 PM

Originally Posted by scoflaw

Don't forget that you can buy the part at NAPA for less than half the $

Which brand did u get? Is it marine safe/ignition protected?

**Last Dollar** · 10-18-2012, 10:31 PM

Originally Posted by psubill78

Which brand did u get? Is it marine safe/ignition protected?

The brand I bought was from iboats.com and it was Sierra. I'm sure it is marine compliant. Napa did not carry it and this brand was cheaper than the Mercruiser part.........and since I will always carry a spare....and since the Mercruiser original OEM failed I think this brand will work fine.