Well I read this post serveral times thinking I should change my IAC's And yes I do work at a ford dealer so easy to get the parts right. Well I did not change them, we go out on the lake last week and what happens? An IAC goes out, I get the 3 beeps when I turned on the key on, started up but going to take off the warning beeps 2 times again then at idle the engine stalls out, checked the IAC and found it looking just like the picture.Ran to NAPA to get a new IAC, installed it and fix the problem. Thay crossed the Ford part number. Yes I will do the other engine before I go out again. So if you have a 496 MAG HO replace your IAC'S...

Sorry to hear you had this problem...seems to be a 496 common concern? Does Merc have any recalls or bulletins? At least you caught this before any harness or ECM issues.

Anybody have any insight as to why a Motorcraft part is on a GM engine? I thought Motorcraft was a Ford supplier? Is this a Merc specific change or do all 496's use this IAC (i.e. the engines in the trucks, etc)?

On the 8.1 trucks, they're "fly by wire" so the air is controlled by the throttle position instead of an IAC I'm almost positive. The throttle body on the Merc version is different for sure.

you are correct...

Motorcraft is Ford, the parts retailer just like AC/Delco is to GM.
I hate to assume but here goes...GM used a lot of electronic throttle (drive by wire) bodies with the with IAC function done there...does your 496 have a cable operated throttle? Also GM used stepper motor IACs which could not be 'feathered' as easily like a solenoid during decel.
Hey, it's Merc...why can't anyone seem to find fuel injectors for my 575s...GM TBIs...Merc discontinued the injector and their p/n doesn't cross?


Lots of response while I'm typing. LOL.

Port or Starboard engine, mine was starboard, just curious.

It was the port side I had the concern with.

Anyone have the CORRECT part num for Motorcraft iac valve. Cx1946 is not it. Looking for the EXACT replacement. 496 mag.

I've heard it's the same as the one on a Ford Windstar. I've also heard sometimes the connector is in the wrong position so be careful. Motorcraft CX1766 maybe the right one but don't quote me on it.