Results 1 to 8 of 8
  1. #1

    Default 2002 350 MAG MPI IAC Issue

    I am having issues with a Mercruiser 350 MAG MPI, serial #OM254958, that has an IAC that is not responding. Here is the background on it. We bought the boat last year at the end of the season and I noticed that it had an occasional hard starting condition where it would start but idle low and stumble until you bumped the throttle. This season the condition continued and I started to investigate the issue. I noticed that the engine does not throttle up when cold and then return to idle after it warms up. I removed the original IAC and cleaned the passage on both sides of the butterfly and everything is clean. The IAC appeared to be stuck at the pintle so I ordered a replacement IAC. I installed the new IAC, cycled the key switch for 10 secs. a couple of times to seat the pintle and then started the engine and the condition remained. I located a copy of Scannerpro for the engine and all four readings related to the IAC show the IAC steps when cold (70 deg) at 125 then slowly returning to around 50 when warm. This appears to be within the specs for the ECM. Next I purchased a noid light kit that has a light specifically for the GM IAC. I hooked up the noid light and turn the key on/engine off and the red and green lights flicker briefly indicating they are receiving the command to retract to increase idle for startup. The lights both then stay solid red and green. When I turn the key off the lights flicker again indicating they are receiving the command to extend for shut down. I am at a loss as to where to proceed next with this. Any help is appreciated.

  2. #2
    Join Date
    Jun 2008
    Island Heights, NJ,

    Default Re: 2002 350 MAG MPI IAC Issue

    Check for a vacuum leak in the line between the IAC and the engine.
    Capt Bob
    1969 23ft ChrisCraft Lancer
    Merc 5.7L 260HP/ Volvo 280
    1972 22ft Bristol
    Honda 7.5HP 4 stroke Long shaft

  3. #3

    Default Re: 2002 350 MAG MPI IAC Issue

    I saw the vacuum line that was attached to the same port as the iac intake. How would the leak make the iac in effective?

  4. #4
    Join Date
    Sep 2010
    Jersey Shore

    Default Re: 2002 350 MAG MPI IAC Issue

    You posted the drive serial number.
    Dockside Marine Services
    Jersey Shore.
    Mercruiser/Mercury Certified
    Let the insanity begin.

  5. #5

    Default Re: 2002 350 MAG MPI IAC Issue

    Thats weird about the serial number. I am pretty sure that is what was on the flame arrestor cover. When I type it in it on some of the parts search websites that number comes up as an alpha drive. I have a Bravo drive. The throttle body breakdown and IAC part number for the 350 MAG alpha/bravo with serial number between OL331599 thru OM299999 definitely matches my engine. I will double check the number tomorrow.

  6. #6
    Join Date
    Sep 2008
    Maryland - USA

    Default Re: 2002 350 MAG MPI IAC Issue

    The 'search by serial number' feature on the parts page, here, took me to the drive section, too....however, using the search by model, the sub selection had about 6 different intervals and the serial number given was in the second group.....

    I could be the IAC itself is fine but the port has clogged with carbon....have you checked to make sure the port is open?

  7. #7

    Default Re: 2002 350 MAG MPI IAC Issue

    I have sprayed throttle body cleaner down the IAC port and it is clear.

  8. #8
    Join Date
    Sep 2003
    New Tripoli, PA, USA!

    Default Re: 2002 350 MAG MPI IAC Issue

    I cleaned the IAC on my truck--several times--and it always screwed up again. I suggest you replace it.


Similar Threads

  1. 2002 9.8 carb issue
    By Wfc3 in forum Nissan Tohatsu Outboard Forum
    Replies: 1
    Last Post: 06-04-2017, 06:53 AM
  2. 2002 50hp 2stroke issue
    By tommy24a in forum Mercury Mariner Outboard Forum
    Replies: 4
    Last Post: 07-10-2015, 06:14 PM
  3. hona 225 2002 cold start issue
    By aristakat in forum Honda Outboard Forum
    Replies: 7
    Last Post: 01-12-2015, 08:47 AM
  4. power steering issue 2002 5.0
    By tagat13 in forum Volvo Penta Gas Engine Forum
    Replies: 0
    Last Post: 06-22-2010, 08:32 PM
  5. Alternator issue 2002 225 h
    By aristakat in forum Honda Outboard Forum
    Replies: 11
    Last Post: 02-06-2010, 01:25 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts