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2001 Monsoon EFI Bogging down


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WaterskiCowboy
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I have a 2001 Sunsetter LXI (direct drive) with fuel injected Monsoon engine that I have had since new.  It started to have some issues last year that could be described as bogging down and shuddering.   When I got it out from storage last season (I always put it away with chevron fuel and fuel stabilizer) the boat wouldn’t get above 15 mph for the first 4 hours of operation so we pulled kids on Hydroslides and made the best of it.   Then party through the day it started running fine.  It lost about 2mph off the top end and I just kept running AMSOIL performance inhancer through the fuel to clean out the injectors.   

 

We were plagued with Fires this last summer and the boat only made it out about 6 times.  Then just before putting it away for the winter it started bogging down again and restricted to about 18mph and shuttering/vibrating when the throttle was pushed past where it would accelerate.

 

I figured I’d just order and change spark plugs and fuel filter.   It didn’t  look like they were the issue but I figured they could use changing since they were last done about 8 years ago along with cap, rotor, and wires.   

 

I’ve been reading online about an ICM ignition control module and Coil as well as Throttle Position Sensor and Air Flow Sensor.  Is there an easy way to check these?   I have a OBDII reader but I think the boats use something different from what I read online.   Any input on what to check and how to do it would be greatly appreciated.   

Edited by WaterskiCowboy
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Before you get too far ahead of yourself, I applaud your idea to replace the spark plugs and fuel filter, but given the age of your boat I highly suggest replicating the cap, rotor, wires, and a new coil before continuing with any other maintenance troubleshooting.  All of these are relatively cheap and are no doubt well beyond the scheduled expiration date if they are original to your boat.

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WaterskiCowboy

Cap, Rotor, Wires, and Plugs were last changed 8 years ago with zero affect (positive or negative) to the running condition.   

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9 minutes ago, WaterskiCowboy said:

Cap, Rotor, Wires, and Plugs were last changed 8 years ago with zero affect (positive or negative) to the running condition.   

Did your issues start 8 years ago, or recently?

 

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WaterskiCowboy

Have never had a single issue until this last summer.   Thought it might be fuel related at first 

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electricjohn

I would look into the ignition module under the distributor cap. See if the dot on it is still white. Then look over the pick up wheel. May want to check your timing since your doing a tune up.

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10 hours ago, WaterskiCowboy said:

Cap, Rotor, Wires, and Plugs were last changed 8 years ago with zero affect (positive or negative) to the running condition.   

Great, last time you changed tune-up items before you had trouble with them.  It looks like you may not have been so lucky this time. 

Throw the poor thing a bone and at least change the cap and rotor.  If you insist (like I would) that eight years just isn't time to need a full tune-up, use your pocket knife to scrape the oxidization from the terminals inside the cap and at the edge of the rotor.  If the carbon center contact in the cap is worn out or broken, you may need that new one after all....

In the chance that you don't actually have a pocket knife, I strongly recommend the Case Medium Stockman with carbon steel blades.

https://www.casexx.com/Pattern/DisplayPattern.asp?PatternAutoID=30

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Fought some similar battles with our 98 monsoon. 
 

Sounds like you’ve given her a basic tune already. 
 

I’d pull fuel injectors and either clean them yourself or send them out if you have the time. Fairly easy to do, first time I pulled mine lots of debris in the screens blocking flow to the point Cylinder 7 or 8, whatever one is closer to pump wasn’t even firing regularly. 
 

TPS is cheap as well, and could cause a rich condition leading to poor performance.  If it smells rich at idle or you’re seeing gas in your exhaust I’d start there.  

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For only a refundable deposit, go to autozone or whatever is nearest you and get their fuel pressure test kit. Test your fuel pressure for zero dollars first.

How awesome this is the first issue your Malibu has had essentially it's entire life. 

Steve B.

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WaterskiCowboy

Thanks to everyone who responded to this thread.   Problem Solved!    I removed the fuel pump and cleaned off the metal filter inside on the bottom.   Honestly, It didn’t look that dirty and you could see through it at about 80-85% but apparently it was enough to be the problem.   I can go over 15mph again.  Thanks!  

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WaterskiCowboy
23 hours ago, CoMtnBu said:

Fought some similar battles with our 98 monsoon. 
 

Sounds like you’ve given her a basic tune already. 
 

I’d pull fuel injectors and either clean them yourself or send them out if you have the time. Fairly easy to do, first time I pulled mine lots of debris in the screens blocking flow to the point Cylinder 7 or 8, whatever one is closer to pump wasn’t even firing regularly. 
 

TPS is cheap as well, and could cause a rich condition leading to poor performance.  If it smells rich at idle or you’re seeing gas in your exhaust I’d start there.  

I fixed the major problem but I’ll definitely be looking into doing this.  After 20 years I’ll bet the injector screens could use some cleaning.     
 

I’ve been thinking it was a little on the rich side, but it’s fuel injected so I didn’t think there was anything that could be done about it.   Just figured it was something I wasn’t aware of when I was younger.  

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Your boat has been almost maintenance free. A lot like my 02. Don't feel bad if it needs a pump not long from now. I try to replace the cap and rotor every 2 years and plugs maybe every 3. Clean the plenum fully, and that is more taking your time for every inch in there.

Because I had so little issues, I started replacing things like the coil, wires, idle air controller, throttle position sensor just to let her know I cared.

It's always started easy, but now it is a half a click and she hums. I let it warm up fully and at that point the boat wants to do nothing but rev freely.

Steve B.

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