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  #1  
Old 05-15-2014, 03:23 PM
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boat dies when pulling back towards nuetral on throttle

Took the boat out last weekend for the first time this year. When pulling throttle back towards neutral in forward or reverse the engine wanted to die. Sometimes it did sometimes it picked up. Rmps drop to around 400 before it wither died or picked back up. Only way I could stop this was to gradually pull the throttle back to idle. Any thoughts?? 2005 x-45 with 8.1L
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  #2  
Old 05-15-2014, 09:17 PM
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IAC (idle air control) or TPS (throttle position sensor) would be my first guess.
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Old 05-15-2014, 09:48 PM
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I second Brian's reco. After that go after fuel pressure/delivery.
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Old 05-16-2014, 07:10 AM
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Is there an easy way to test these or just replace? Thanks
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  #5  
Old 05-19-2014, 12:46 PM
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IIRC this was a common issue with the L18 around that time. Before throwing parts at it check with your dealer to verify you have the latest software version for the L18 from Indmar.
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Old 05-19-2014, 04:18 PM
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I had a strange similar issue with my 06 X15 last year (MCX 5.7 liter). Going from drive to neutral, the engine would either want to die or would rev up. My first thoughts were to check the wiring and search the internet for clues. I came across an article that said this behavior can sometimes come around due to poor or degraded grounding in the MC speed control switches (i.e. thier version of perfect pass). So I took the switches out and put di-electric grease on all the terminals. Did the same with the TPS harness. I did not touch the wiring to the idle air control just yet, as I already made two changes and wanted to know what real issue was. Turns out I did not need to touch the idle air control wiring at all. The issue is now completely gone now and I spent zero dollars fixing it. I suggest you start your investigations on the MC speed control if you have it. Next, put a little grease on the TPS electrical connector.

Good Luck and I hope you have similar success.
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  #7  
Old 05-19-2014, 04:27 PM
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It was a busy weekend with kids sports so didn't even get a chance to work on it or anything. thanks for the heads up and hopefully will be diggin into it before the big weekend.
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  #8  
Old 06-15-2014, 10:20 PM
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After two weeks in Houston on business I finally got a chance to start checking wiring and such but no luck. Took it to the dealer and hooked it up to the computer. Computer is telling us that the idle air control is bad so you guys were right. Bad news is that it is integral with the throttle body. Is the throttle body the same whether marine or not? Indmar was closed Friday by the time we figured it out so no idea on cost.
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  #9  
Old 06-15-2014, 10:23 PM
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Should be the same - unless Indmar did something specific like they did not LT1 in the 90's
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Old 06-16-2014, 12:31 PM
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Just heard back from dealer and indmar wants $481 for the throttle body and $11 for the gasket. I think I will take it to an automotive store to see if they can match. Dealer also thought it was the same, but wont get it from anyone but indmar.
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