Offshoreonly.com - Engine loading up at idle MPI

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so i was right about a bouncing fuel pressure needle/

Quote:

Originally Posted by BUP (Post 4703811)

so i was right about a bouncing fuel pressure needle/

Yes you were, dose the needle bouncing indicate an issue with the fuel pressure? I guess I assumed it was from the vibration of the motor and it was normal, but that is the first time ive ever had to check fuel pressure so I really don't know if it is normal.

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Originally Posted by F-2 Speedy (Post 4703592)

ID replace the IAC, might have to open the butterflies just a tad with the idle screw, I had one that looked normal on the laptop but would not idle right and stall when put in gear, replaced it and new plugs and was fine....wheres the TPS volts suppose to be set,

im starting to lean towards replacing the IAC also since everything else seems to be checking out fine. I think im going to remove it, clean it and try it and if there is no change, then replace it. I hate to throw parts at it since I just bought that scanner with the hopes that it would save me money by not having to throw parts at it but I guess it was not a win this time. I could not find any info telling me were the volts should be set at for the TPS in my mercruiser books, only info about install and removal. I did a search and found somebody stating that for a 454 mag mpi gen v it should be between .45 and .65 volts so I set it at .55 volts.

I opened the secondary butterfly valve enough so that when the engine was warm and idling, the IAC was hovering around the #40 position. one time we were out on the boat and going threw a long channel before getting to the ramp, and the dying issue became a major issue while I was trying to dock, I opened the engine compartment and turned the idle up and it seemed to help the issue a lot. when I put the scanner on it (next time we went out), the IAC was hovering around #3 or #5 position. I know that is not correct because it doesn't give the IAC enough "room" to do its job but it helped the issue, that is a "+1" on making me think maybe the IAC is faulty in a way that its not moving fast enough to do its job. of course im just brain storming.

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I did not notice a difference pulling the spark plug boots off one at a time. I did shut it off and re-start it.

Was hoping you would pull and reinstall the plugs with the motor running. Doing this method you can here the difference before/after and compare.
The timing is moving around, but this can also be to compensate for other issues like the IAC.

Quote:

Originally Posted by BUP (Post 4703654)

Totally wrong info about spark plug wires actually in marine apps they ARE OFTEN NOT CHECKED NOR CHANGED ENOUGH, must have been an auto mechanic that mentioned all that for they rarely ever need changing. .. .

There is many reasons why spark plugs wires in marine apps need to be changed and correct wires as well. The main issues for a jist of it ----- For one is the heat soak in an marine engine compartment last for hours and is way hotter than an auto would ever be.

Would like to add a correction. Heat and heat soak is way worse in cars. Far, far worse.

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Originally Posted by AllDodge (Post 4703845)

I had a bad experience one time while I was trying to shut off a snowmobile that started dieseling, it was late at night but that shock gave me the energy to power on for another couple hours until I go my sled running. I was about 15 mins from loading it up and going home LOL. assuming that you have tried this before and snowmobiles must be different, is it safer to take the plug off at the cap? or should I be taking it off at the spark plug its self?