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1999 Merc 350 Mag MPI Bravo. My engine drops to low rpms or…

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1999 Merc 350 Mag MPI...
1999 Merc 350 Mag MPI Bravo. My engine drops to low rpms or stalls when putting it into neutral. The engine runs fine at higher rpms. I replaced the IAC Valve but the problems remains. When running at higher Rpms and then shifting into neutral there it back pressure coming out the IAC adaptor connected to throttle body. any ideas?
Submitted: 3 years ago.Category: Boat
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Customer reply replied 3 years ago
The problem only happens periodically since replacing IAC valve
Answered in 6 hours by:
6/12/2015
Marine Mechanic: Jason, Marine Mechanic replied 3 years ago
Jason
Jason, Marine Mechanic
Category: Boat
Satisfied Customers: 18,172
Experience: Degree in Marine Technology. Gas and diesel marine mechanic.
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Good morning, my name is ***** ***** am I speaking with? Have you checked the engine compression yet?
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Customer reply replied 3 years ago
My name is ***** ***** No I have not checked compression. The boat runs flawless when at 900rpms or higher. The engine has no power lost above 900rpms. When shifting from a high rpm load to neutral there is ton of back pressure release from IAC adapter connected to throttle body
Marine Mechanic: Jason, Marine Mechanic replied 3 years ago
That pressure makes me wonder if you have a burnt intake valve. And it only takes 1 to cause the issue. There are a couple of ways to check for this. Compression test is one. Checking engine vacuum and looking at both the overall vacuum level as well as seeing if there is any flicker on the needle is the other way to do it.
So that's what should be done. Are you able to do these checks and get back to me, or what would you like to do? -Jason
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Marine Mechanic: Jason, Marine Mechanic replied 3 years ago
It looks like you read my response and logged off. I do want to make sure I get all your questions answered. If you do have a further questions by all means feel free to reply back. If not,
Just incase you do not understand the way the website works (and some folks do not). You do have to put forth a positive rating in order for it to credit me for helping you. When ratings are not done, the website simply keeps your deposit and they will not credit me. Please let me know if you run into any problems or errors when trying to do it. Questions do not lose out, so if you have to come back tomorrow or next with follow up questions to this you still can even after doing a rating
If I do not hear back from you I thank you in advance and good luck!
Jason
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