To Idle Air Control or Not
Autodog61
Member Posts: 92 ✭✭
Ok, been a while since I posted and want to get input on IAC for my 6.2L's on my 342. I went out two weeks ago and starboard engine, after a 3,500 RPM run up would die when I idled back. the only way I got it to restart was throttle in neutral to about 1,500 or higher but when I dropped back to idle to engage drive it would die. Limped it back to marina with both at 1500ish RPM or there abouts but of course pulling down into slipway at idle in gear, starboard engine died. And, of course, loss of power steering due to starboard engine out Ugghh. Got it slipped with some anxious moments. Mechanic later explained was a bad IAC. Haven't taken out since he replaced IAC and tightened throttle cables but I am sure he is correct. What irritates me to no end, the starboard IAC was replaced in 2016 (whistling sound from it probably sucking that silly white filter in clued in along with Code check that it needed replaced). Port IAC was changed last year. I have put maybe 25 hours on it since 2017. No way the starboard IAC should have been bad. Mechanic stated Mercury revised the IAC design few years back and they are prone to failure. He wasn't surprised it failed in less than 2 years (then again, he was the one who replaced it in 2016). I did have a spare Sierra brand IAC on board but, being the typical boat yard, "we only replace with Quicksilver related parts and sierra is a knock off brand". I am not torqued at the mechanic, because I noted myself in the recent past the starboard engine was "whining" a bit more than usual over past few outings. Now I know why. I see in another post, its not uncommon for the valve to get gummed up. So, some suggestions needed for the knowledgable -
Is this the correct IAC for the 2002 6.2L (Marina referenced part number 862998 on the invoice)-From this vendor its $169. Marina charged $279 (plus gasket at $4.30) https://www.mercruiserparts.com/862998-valve-idle-air
Mercury-Mercruiser 862998 Idle Air Valve
Any ideas on the quality/difference of Sierra vs Quicksilver? Looks like Amazon directs you to a this one (seems the same other than blacked out and clocking difference of elect. connect). Assume I will actually have to look at current before I buy unless you all can say for sure which one.
New Mercury Mercruiser Quicksilver Oem Part # 8M0045797 Valve-Idle Air $118
2. Another thread suggested to leave out the mufflers. Wondering...…., Yes, they prevent oils and such from getting into intake but......I have also heard if they get gummed up they can be sucked into the intake. Leave in or leave out? And, where is it located?? under the plunger? And why are there two pieces rather than 1 (to ensure the intake sucks a piece in when it gets gummed up?) I suppose this is good reason to put IAC/Muffler on annual evaluation list.
3. Do they need calibration after install? Mechanic said no. ECM will relearn on its own. BUT, another thread said to disconnect power . I suspect this is to force the ECM to relearn. Which is it, no disconnect needed and ECM will relearn or disconnect power?
I haven't looked but I am sure its either in front under the spark arrestor (on the throttle body) or behind (as another thread indicated) so should be easy to find. I am going to buy 2 just to have on hand as well as 2 TPS. Again, Mechanic said TPS doesn't have adjustable mounting slots so no calibration with them either. However, on my 92 Camaro (last TPS I replaced) there is a goofy OBD I silly process for forcing the ECM to relearn Positions and appropriate voltages. Havent messed with OBD II systems. Oh yea, and on the IAC plunger, I will try to see that they are both in same position when I install new one. Maybe that's the key to not having the ECM not required to relearn, making sure the plunger is in same position on old to new.
Thanks ahead of time for input. I have a lot to learn still.
Comments
Mark
2019 MTX20 Extreme
Thanks for the input so far. Really, I do these discussions to help myself and to help others learn. In this case, I want to be prepared when the IAC fails again by having sensors on the ready and knowing how to replace on the fly. I hated having to limp back to the marina and worse, trying to maneuver into the tightest spot in the marina with one engine and no power steering. Ugghh.
So, interesting comment about sierra and the Ford Windstar. I think I will stay away from generic brands like Sierra now. Also, another thread I read suggested not to use automotive for Marine application. Generally, I would keep to quicksilver brand as they are specific to marine but in the case of an IAC, as Skennelly points out, the 02 Ford Windstar shares the same IAC as the 5.7L (6.2L I believe is a bored and slightly stroked 5.7L). What I find really interesting (but not surprised) about is the Windstar is a ford and the 5.7L/6.2L is a GM product. Likely attesting to the generic nature of sensors like the IAC. Benefit of course is about $120 savings.
I went through the Mercrusier O&M manual and was disappointed to see like three lines on the IAC removal/replacement (see Section 5B think it was page 49) and none if it was helpful other than sort of looking like the clocking for the electrical connector is like the first photo above and that the location is either behind or to the Pot side of the throttle body. Felt like I was in high school again reading a Chitons Manual) I will look this weekend, take some photos to confirm clocking and location and share with others. Again, the idea is to learn how to manage myself and avoid a $400 service call out and get me home if it happens again outside a 25 mile radius of my home marina. Having spares and knowledge....A good thing, Y'all.
Regards,
Ian
The Third “B”
Secretary, Ravena Coeymans Yacht Club
https://www.rcyachtclub.com/
Ok, so I went to boat today and took a few photos of the location of TPS and IAC. OF course my IAC is a shiny new sliver one just like I posted in first photo. I have included several photos to support those who want to have a spare or two at the ready should they loose idle, particularly on starboard engine with the power steering pump.
Overall view of engine sans carb cover
Close up of IAC - Note clocking position for electronic plug
Close up of TPS. Sorry for the small text. Photoshop elements doesn't let you see actual as you edit photos. Yet another irritating thing in my book. Note TPS doesn't have adjustable (oval for twisting in the mount prior to tightening) holes for calibration. Mechanic was correct. THese are simply plug and play. One of the benefits I suppose of ODBII technology.
One last photo of the IAC again. Note location is on top of intake behind spark arrestor.
Now for my thoughts on my questions.
1, I clearly have the silver Mercury-Mercruiser 862998 Idle Air Valve. After a closer look at the two different part numbers above, I see they are both clocked at 270 degrees. So for me, I will spend a bit more coin and replace with Quicksilver part at $169 rather than a $40 automotive IAC. Automotive would probably work but for me, I just cant put an automotive part on a marine engine Especially given they are $100ish different in price and doing it myself will safe probavbly $200 samolians. From this thread though, you the reader, can make your own call. Maybe install a cheapie but have a more expensive quicksilver on had just in case. Also, the two mounting bolts look to be a torx head. So, to replace yourself on the fly, make sure who have torx bits handy in the tool box.
2. The mufflers. Although we didn't get clarification from others yet, I am going to assume the muffler(s) install between the IAC case and the manifold/intake base. Key will be when you remove the old IAC, observe closely as you pull apart to see how they are positioned (assuming prior guy installed them correctly). For me, I will use them but will check every two years and will have two sets of these on hand as regular maintenance parts.
3. Again, no conclusive information from others on Calibration. I am going to assume mechanic told me correctly, no calibration required. Same for the TPS - Note there aren't oblong holes where the mounting screws go to be able to twist the TPS about 10 degrees forward or reverse. Again, ECM likely has a specific set BIN for the TPS location and with OBDII technology, no longer need to calibrate. For those not aware, the Throttle Position Sensor (thus the acronym TPS) reports a voltage to and from the ECM as you throttle up or down. The ECM expects this voltage (don't quote me but should be like 0.5v to about 0.75? volts as you roll ffrom Idle to full throttle). If it doesn't see this it will throw a code.
If I'd been thinking the other day when my IAC crapped out (unknown at the time what the cause was) I would have pulled out my Rinda Techmate and I would have seen a bad IAC code. Instead I panicked and sent it to my marina mechanic to R&R. Had I used the Rinda could have saved probably $300 and about 10 additional days. Live and learn.
And finally, a fourth and final question. The prior boat owner had a bag full of PCV and PCV grommets/elbows. The broker I bought the boat from said the owner told him he was constantly having to replace PCVs. Although I haven't looked, I thought I read somewhere the 6.2L doesn't have a PCV system. Apparently not true what I read. Does any one know whether our 6.2Ls are prone to PCV clogging?
Forgot to post photo of PCV the prior owner had stockpiled. Here are the photos with the part number:
06 Rinker 270
The $118 on Amazon, is that OEM? Weird that its black.
06 Rinker 270