5.0L MPI Idle Air Control Valve OEM vs Aftermarket

[rkilpa]

2011 5.0L MPI with 175 hours.

My 5.0L has been shutting off intermittently while docking. When I need to go from neutral to forward or reverse and back to neutral several times while at idle speed sometimes the motor just shuts off like the key was turned off. No sputtering. No reduced RPM's. Just cuts off. And not all the time, just occasionally. I'm pretty sure it's only happening when going from gear to neutral. I usually turn the key off and then restart with no problems.

The last time this happened when I restarted, I did not turn the key to off first. I turned the key to start from the run position and then I got the 2 beeps every minute alarm until I turned off the key and restarted it again.

I have read that a possible cause would be a failing IAC valve or a dirty IAC filter/muffler. I don't have a scan tool and I know it's wrong to replace random parts without knowing the true problem, but I have seen IAC valves with gasket for under $40 and figured it would be a low cost risk to see if this helps.

Of course the $40 ones are aftermarket China parts. The OEM and Quicksilver part number 862998 run $160+ plus $8 for the gasket plus $12 for the filter/muffler.

I'm wondering if anyone has had any luck with the aftermarket version, or should I only consider OEM? If the difference were only a few dollars, I always prefer OEM. However, at 4 times the price...

Thoughts about the issue? Does it sound like this is the part I need, or could there be something else I need to look at?

Thoughts about aftermarket vs. OEM?

 

[Bt Doctur]

The IAC is a ford part

 

[alldodge]

Throwing parts at a problem can get expensive.

What are you idling at in gear and neutral?
Try a few times to see if things change. Would also need to check with an accurate meter and the boat Tach may or may not be accurate

Would also be good to know the fuel pressure?
Should be 43 psi

And what is your serial number???

Edit: and assuming this is mechanical shift and not digital (drive by wire)

 

[RaceCarRich]

Can you see if your tripping the shift interrupter switch due to a worn shift cable? It’s supposed to trip only momentarily coming out of gear due to force required but if cable wears it might have enough force to trip the switch other times when it shouldn’t.

I’ve been using an auto parts store IAC for 2 years with no issue. Think it was standard ignition brand part # AC423.

 

[Scott Danforth]

standard motor products is one of the OEM providers

and yes, Mercruiser uses a ford IAC because they only had 2 pins left on the ECM, and the GM IAC required 4

 

[rkilpa]

And what is your serial number???

Edit: and assuming this is mechanical shift and not digital (drive by wire)

Serial # 1A639709

I can't look under the engine cover now because the boat is 200 miles away. Would the serial number tell me if I had a mechanical or digital throttle body?

I found a nice video showing someone replacing the IAC on a 2014 model that was mechanical. Would it be safe to say that a 2011 model would be mechanical, too?

 

[alldodge]

If you have cables from the throttle handle to the throttle body and shift plate then its mechanical. If you have wires going to TB and shaft cable then its digital

Most will have mechanical

Your serial numbers helps but doesn't tell me which you have, but would tell a dealer because they have access to better data

IAC 866295A02
and not saying this is the issue yet

If yours is mechanical this is the parts list of the TB
https://www.mercruiserparts.com/bam/subassembly/31757/15045/80

 

[Bt Doctur]

you list as a GEN II drive so it could be just the shift cable going bad , the lower cable that goes from the plate to the drive

 

[rkilpa]

you list as a GEN II drive so it could be just the shift cable going bad , the lower cable that goes from the plate to the drive

I would think it would be an issue with something electronic if it caused the 2 beep alarm to go off. However, the alarm has never come on before when the stall at idle has happened in the past. Maybe it's just coincidence, but the 2 beep alarm started sounding when I turned the key to start from the run position instead of turning the key off first. I usually have time to turn the key off. but this time I needed to get the engine running quickly to avoid a hit.

 

[Searay205]

my 2011 was doing the identical thing EXCEPT no alarms. My shift cable was bad. If your shift cable is bad you shouldn't get an alarm, the switch mechanism is working as it should, it killing ignition to take load off clutch problem is it kills it to long since cable is stiff. I actually changed my IAC first thinking it was the problem. I got the replacement at Autozone lifetime warranty for $30? you should be able to google the part number. You need to read the code.

 

[rkilpa]

It was just pointed out to me that an automotive part or Chinese knockoff part would more than likely not be marine certified.

The Sierra part #18-7701 is certified to be ignition protected and will not cause any spark when engaged inside the engine room. Since I would prefer not to go "boom" when starting my boat, I purchased the Sierra part with gasket for just under $100. Not quite just a $40 gamble, but at least it's not $170+.

I will report back in a couple of weeks with the results after I have a chance to install it.

 

[RaceCarRich]

Ouch! When mine needed replacing, I confirmed with the experts here that what I read elsewhere was correct... this is one part that did not require to be marine certified (like say a starter) as there was no spark or explosion risk. That was one expensive box they put the part in.

When you get to the boat, you may want to observe the shift interrupt switch before installing the IAC. Costs nothing to look while there. The switch shouldn’t close going into gear, only when coming out of gear.

 

[Scott Danforth]

It was just pointed out to me that an automotive part or Chinese knockoff part would more than likely not be marine certified.

The Sierra part #18-7701 is certified to be ignition protected and will not cause any spark when engaged inside the engine room. Since I would prefer not to go "boom" when starting my boat, I purchased the Sierra part with gasket for just under $100. Not quite just a $40 gamble, but at least it's not $170+.

I will report back in a couple of weeks with the results after I have a chance to install it.

the SMP part in post #4 is the exact same part as the mercruiser part.

 

[rkilpa]

SOLUTION:

I replaced the IAC valve with the Sierra part and replaced the IAC filter with the OEM Quicksliver part. I don't know if I could have just replaced the dirty filter and fixed my problem, but since I had the new IAC valve and the boat is 9 years old, I went ahead and replaced it, too. I'm pretty sure the filter was clogged and not letting a lot of air in.

I took the boat out and could not get it to stall even when I tried. I also noticed that I am now able to start the boat with just a turn of the key and it idles smoothly without giving it any throttle at all. When I first got the boat, I had to treat it like my old carbureted 1997 4.3 V6 and start it with some neutral throttle until it warmed up a little. I just assumed this is the way it was.

I now know that there is a IAC filter that needs to be replaced periodically. I am happy that it is accessible without removing any parts other than the engine cover so I can check its condition easily. For some reason I was thinking it would be inside the housing that the IAC valve connects to and would only be accessible when replacing the IAC valve.

I am still learning the differences between my two boats and I really appreciate all the great help and advice you guys provide.

Here's a picture of the dirty filter next to a new one. I think you will agree that this was the problem.

 

[tpenfield]

Nice work getting it fixed . . .

Aren't MPI engines fun? In my travels working on boat engines, I've come to realize that the problems are hardly ever - to the point of never being . . .
- spark plugs
- ignition wires
- coil
- IAC valve

I got a bunch of IAC valves in my parts drawer that never fixed 'the problem'. . . they are automotive parts and SMP is the OEM.

Also, just about everything comes from China, it seems. So, buying it in a Mercury/Quicksilver package just makes it cost more.

FWIW - In working on my MPI engines, I usually take the suspect part out and check it for the OEM numbers . . . the sensors are typically a GM part . . . so I buy the GM part at 1/4 the price.

 

[Lou C]

That is great information for anyone who has an engine with at IAC valve!
I am amazed by what Merc Volvo and OMC charged for parts they bought from other suppliers. OMC/BRP wanted $230 for a Carter marine mechanical pump you can find at Jegs or Summit racing for $85-90. Figure out who made it find the part # on it and start looking

 

[Stinnett21]

I also have an MPI and I learned the same lesson. It helps to keep the flame arrestor clean. I spray mine with brake cleaner every off season and replace the IAC muffler in the process.

 

[Lou C]

I do the same, the flame arrestor gets surprisingly dirty. I do like my stone age engine very much vs MPI (points distributor, Quadrajet carb, mechanical fuel pump) so much that when I need a new engine I'm going to find a reman 4.3 so I can keep using the old style mechanical pump etc, intake manifold heated choke, etc. Its old and it works and you can fix it in the driveway with simple tools + dwell meter + timing light, just like we did with our cars back in the '70s.

 

[Scott Danforth]

its threads like this that make me glad I have a carb......

 

[Stinnett21]

I'm not a motörhead but I love my MPI. Strong, fuel efficient, don't have to wear out the center button on my 3000 controller, Vessel View, hit the key and go. PITA to fog though. Remote tank. What a mess.