New IAC valve needing ECU reset?

Drafter

Drafter

Active Member
Oct 5, 2017
249
Grand Lake O' The Cherokees, Oklahoma
Boat Info
1998 400 Sedan Bridge
1969 Boston Whaler 13
Engines
Horizon 454 380's
I was having some issues with my starboard motor shutting down after coming off of higher revs back to neutral. 98 Gas 7.4 Horizon 380's. With a little research, I decided to drop in a new IAC (Idle Air Control) valve, as I understand that they get carboned up and get stuck.
Now that it has been installed, the motor idles at 2800 rpm. It will rev beyond that, but returns to 2800. I understand that this is a pretty common thing, as the ECU needs to reset itself. Lots of videos and info with cars and trucks, but can't figure out how to do it on a boat.
I've done the remove and replace battery connection to that engine trick.
Anybody have any thoughts?
 
Probably not an IAC issue, it was the newer ones that had the issues. Check to see what your TPS is doing
 
hello, i had the same problem.i change the IAC but still the same.after cleaning the injectors the problem was over.
 
Thanks Japio. It was the IAC. It was idling high because I still needed to drop on new gaskets. It was pulling in too much air and trying to compensate. New gaskets were the immediate fix. No ECU resetting needed. Runs like a top now.
 
Mine was acting up, thought it was IAC until we replaced it with no change. ECM was the issue. Sent mine to a place in Long Beach to rebuild but they ended up not being able to. Sent me a new one for a good price.
 
Drafter said:
Thanks Japio. It was the IAC. It was idling high because I still needed to drop on new gaskets. It was pulling in too much air and trying to compensate. New gaskets were the immediate fix. No ECU resetting needed. Runs like a top now.
Click to expand...
What gaskets needed to be replaced after the new IAC installed and not idle properly?
 
Royalboater said:
What gaskets needed to be replaced after the new IAC installed and not idle properly?
Click to expand...
If you are MAG MPI, there are gaskets on the 4 intake tubes that cannot be ignored, and a gasket between the intake filter and the throttle body. Also, make sure your butterflys are REALLY closing all the way at idle throttle. Mine weren't, causing high idle when I first got my replacement motors. That adjustment fixed the air leak and returned the idle to spec.
 
370Dancer said:
If you are MAG MPI, there are gaskets on the 4 intake tubes that cannot be ignored, and a gasket between the intake filter and the throttle body. Also, make sure your butterflys are REALLY closing all the way at idle throttle. Mine weren't, causing high idle when I first got my replacement motors. That adjustment fixed the air leak and returned the idle to spec.
Click to expand...
Thank you. I replaced the IAC today and it seemed to fix it!! I am way over joyed! Been dealing with this issue for a year and a half. Cant get a knowledgeable mechanic to show up.
Casey
Consumer Marine Supply
 
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