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2002 Wakesetter VLX hesitation on acceleration


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Here are the symptoms of my 2002 Wakesetter VLX - Monsoon 325 MPI

  • Momentary hesitation or "bogging out" upon throttle movement from idle or gear, like when pulling up a skier or wake-surfer, then it "catches" and accelerates normally with good power
  • Sometimes there is a bit of a black exhaust cloud (not very big, but noticeable if you're looking) right after the above mentioned hesitation
  • At higher speeds, for instance above 32-ish mph if I've been there for maybe 30 seconds, it will sometimes slow down the rpm for a few seconds, then speed back up, then slow down, etc.

Here's what I've done so far:

  • New ICM* (edit) it died last year and was replaced with the thermal grease underneath.
  • Fuel rail pressure checked at key-up and when running. The numbers were normal - I think 42-ish at key-up? I didn't write it down but I had the specs with me when I did it and it was in the normal range. Unfortunately, the running fuel pressure was done while hooked up to a fake-a-lake and not when under actual load. However, it was also within normal specs. I don't own a tester, so I had to rent it from the local autozone, so I don't have it handy.
  • Checked the cap and rotor, they were replace last year towards the end of the season and still look really good.
  • Checked spark plugs (also new last year) and they look good as well. Proper gap, nice color, etc.
  • New in-line fuel filter
  • Gas in the tank was non-ethanol over the winter with Sta-bil stuff, and I've gone through several tanks of fresh gas since the winter gas. Boat was stored inside, but not heated.

I had the stupid old style kill switch give me problems last year, which is why I suspected my fuel pump was going bad. It wasn't priming at key-up. I then discovered that was due to the kill switch (my gauges weren't turning on either, I just didn't notice that at the time) and it's been replaced. The fuel pump now primes at key-up, gauges turn on, engine starts just fine and idles nicely - no stumbling at anytime other than the situations listed above. Anyway, the possibility of a bad fuel pump let me to the forums here, where I found the before-you-change-your-fuel-pump-read-this post, and I was excited to find out that there is a filter that can clog on the inlet side of the electric fuel pump. My symptoms are exactly what  is described by many when that filter is clogged. 

Last night I pulled the fuel supply line to the fuel pump, removed the hose barb, whipped out my fancy mirror tool and a nice, bright flashlight and was so excited to finally see that clogged up filter and clean it out. And...no filter. I'm not even sure there could be one in there if it wanted to have one. Maybe it could, but regardless, there was no filter to be found. See the attached pictures:

Fuel%20Pump1b.jpgFuel%20Pump2b.jpg

Am I missing something? I'm hoping I pulled the wrong thing and that clogged filter is still in there somewhere to be found. The photo looking up into the inlet of the fuel pump is not great, but I looked at it in person for a while and there is no filter in there.

If it's not the filter, what is my next step to fix the hesitation? New fuel pump? It sounds like fuel starvation to me and I think the pump was whining a bit last time out, but I'm not sure. Could it be bad injectors? I'm not sure - I'm pretty good with engines but I'm not a mechanic and I don't have a lot of experience with MPI. 

Any help is appreciated!

Edited by amacbean
changed ECM to ICM
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You probably should test the fuel pressure under a real load.  Revving the engine in neutral doesn't really ask for much fuel at all.

While you are at it, put a timing light on it to see if you can tell if the timing is jumping around when it happens.

Two hunches I have are spark plug wires and the spark module under the distributor.  You said you changed the ECM, but you may have been talking about the distributor module.  They are not the same.

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Thanks for the suggestions, I'll check the timing and the fuel pressure under load.

The plug wires are probably due to be replaced, I have not checked them for resistance, but they don't exactly look new so it wouldn't hurt to replace them.

Is the unit under the distributor the Ignition Control Module (ICM)? Whatever it is under there, it's the one that was changed. I don't know why I said ECM. Thanks for the clarification!

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  • 3 weeks later...
On 7/15/2020 at 11:01 AM, amacbean said:

Thanks for the suggestions, I'll check the timing and the fuel pressure under load.

The plug wires are probably due to be replaced, I have not checked them for resistance, but they don't exactly look new so it wouldn't hurt to replace them.

Is the unit under the distributor the Ignition Control Module (ICM)? Whatever it is under there, it's the one that was changed. I don't know why I said ECM. Thanks for the clarification!

@amacbeanAny updates on yours?  I'm having hesitation out of the hole.  It will hesitate slightly when I'm pulling up a skier for the first time that day.  After that I'm good.  

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  • 2 weeks later...
On 8/4/2020 at 3:19 PM, kylegansel said:

@amacbeanAny updates on yours?  I'm having hesitation out of the hole.  It will hesitate slightly when I'm pulling up a skier for the first time that day.  After that I'm good.  

Update: Replaced the ICM with a new one just to see if that helped (kept the other one as a backup just in case), changed out the original coil (it was pretty rough looking), and replaced the fuel pump with a new one from SkiBoatPartsOnline. I have not done the cap and rotor (they were new last year) or the plug wires yet. The spark plugs look great.

Result: I don't know. It still hesitates or bogs down about a third to a half of the time when accelerating out of the hole for a second or two, then "catches" and runs fine. There seems to be no surging on the top end anymore, but it surges a bit in gear when going back to pick up a skier, but only sometimes and no one else seems to notice that. Also, I think I noticed a second "hesitation" a couple of times after the first one out of the hole - almost feels like it bogs initially, catches and pulls strong, bogs a little bit at maybe 1/4 throttle - right about when a bigger skier is almost out of the water (i'd give the rpm but i have the perfect pass set to speed mode and I don't have another rpm gauge) and then runs fine for the rest of the run. I'm wondering if it's a fuel starvation issue - do I need to install a low pressure pump in front of the electric high pressure pump? I don't know. Currently though I'm about to start the strut bearing replacement project as I noticed they are worn out so I may not have time to trouble shoot any more until that project is finished. On a side note, we just got back from a trip to Lake Powell for a week and it was epic.

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Hey i have a similar issue, rpm is irregular under 2k RPM, and as soon as I reach 2k rpm it "catches" and perfectly smooth. I will be replacing cap rotor plugs and plug wires in a week or two. Post updates if you fix the problem :)

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I'm just spitballing here, but I'd change the TPS just because they aren't expensive and it's almost 19 years old if original.  Same for cap, rotor, and wires.

 

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It's also a good idea to clean the throttle body before you start throwing parts at it.  Use a can of spray cleaner and follow the directions.  Be sure to get the edge of the butterfly and any side passages. 

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On 8/16/2020 at 5:23 PM, amacbean said:

Update: Replaced the ICM with a new one just to see if that helped (kept the other one as a backup just in case), changed out the original coil (it was pretty rough looking), and replaced the fuel pump with a new one from SkiBoatPartsOnline. I have not done the cap and rotor (they were new last year) or the plug wires yet. The spark plugs look great.

Result: I don't know. It still hesitates or bogs down about a third to a half of the time when accelerating out of the hole for a second or two, then "catches" and runs fine. There seems to be no surging on the top end anymore, but it surges a bit in gear when going back to pick up a skier, but only sometimes and no one else seems to notice that. Also, I think I noticed a second "hesitation" a couple of times after the first one out of the hole - almost feels like it bogs initially, catches and pulls strong, bogs a little bit at maybe 1/4 throttle - right about when a bigger skier is almost out of the water (i'd give the rpm but i have the perfect pass set to speed mode and I don't have another rpm gauge) and then runs fine for the rest of the run. I'm wondering if it's a fuel starvation issue - do I need to install a low pressure pump in front of the electric high pressure pump? I don't know. Currently though I'm about to start the strut bearing replacement project as I noticed they are worn out so I may not have time to trouble shoot any more until that project is finished. On a side note, we just got back from a trip to Lake Powell for a week and it was epic.

@amacbean - do you by chance know what ECM calibration is running on your boat?  My prior boat (2002 Malibu Response LX with the Monsoon was doing EXACTLY the same things has yours...  I have tested, read codes, live data, etc and  replaced just about everything that made sense. All specs and sensors are within tolerance.... I’ve seen so many posts with similar boats and similar issues I’m starting to wonder if there was an issue with the ECM calibration that can’t handle the new corn gas or something else....  I’ve since sold that boat to a friend, so he’s off troubleshooting also - but this one continues to nag at me.....

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Are your fuel lines original?  What about filter?  I was having hesitation issues on holeshot on my '01 and I resolved the issue by replacing my fuel supply line and fuel pump.  I did it all at the same time so I'm not sure what ultimately fixed it, but it's better now.  I'm back to needing less than WOT holeshot on my slalom starts and when you tell it you want to go, it goes.

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My 98 has both an inline fuel filter prior to pump under the floor and one in the high pressure system after the fuel pump..Both should be replaced regularly.........

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***Update***

Ok, it's back to bogging down about %50-%70 percent of the time out of the hole, and now there is a definite second bog down (I would guess around 2,000rpm - again, no rpm gauge except the perfect pass) about the same percentage of the time. It's super annoying. I'm a bigger guy, and it happens right about the time I'm almost up on the slalom. I'll have to run it in rpm mode next time and check the rpm numbers.

I've replaced the inline fuel filter - no change.

I will check the throttle body and clean it.

I had not thought about the Throttle Position Sensor - I'll look into it.

I do need to replace the plug wires regardless, they are original and look a bit rough.

Again, the cap and rotor were new at the end of the season last year and still look great.

Fuel lines probably need to be replaced, but when I replaced the fuel pump a few weeks ago, I removed a couple of them and checked them out as best I could - flow seems to be fine. Probably not a scientific test, though, but they didn't seem to be restricted.

@Gary PelletierI have no idea what ECM calibration the boat is running, but I have run it on ethanol-free gas for a couple of tanks this year with no noticeable difference, except to my bank account. Ha ha.

  • Like 1
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  • 1 year later...
  • 2 months later...

No, the problem is not solved. But I'm currently working on a different problem with the boat that needs to be fixed first. I'm getting an alarm beep when the engine is running, but I can't seem to trace down the reason. Still looking.

 

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