Missing at idle and out of hole

[Lungo]

2004 Wakesetter 23LSV with 340 Monsoon - 635 hours

Recently, the boat started to miss at idle and when pulling out from stop (mostly felt through boat vibrations at idle).  Once you get over about 15 mph (give or take), she smooths right out.

Any ideas on what the cause of this might be?

Recently, I have changed the fuel filter and pulled out the fuel pump to check for debris.  All looked good there. 

I also have been running Stabil Ethanol and Fuel Treatment all summer.  

Thanks for any input.  Season is winding down here in PA and would like to have peace of mind before putting her away for the winter.

[EchelonMike]

If you have not replaced the cap/rotor/plugs, that is what I would start with.  I have a low-hour 2008 Hammerhead powered boat, and threw a misfire code earlier this year.  The tune up work fixed it.  Also picked up a few MPH from the tune up.  Boat back to running great.

[Steve B.]

Lungo you should throw a fuel pressure test kit on the fuel rail and see what you have going. Can check them out from autozone or whoever. Should be 42.5 at idle and wide open throttle.

Steve B.

[justgary]

48 minutes ago, Steve B. said:

Lungo you should throw a fuel pressure test kit on the fuel rail and see what you have going. Can check them out from autozone or whoever. Should be 42.5 at idle and wide open throttle.

Steve B.

2004 to 2006 engines use 4 Bar regulators, not 3 Bar.  The pressure for @Lungo should be more like 56 PSI constant.

https://www.bakesonline.com/media/resourcelibrary/Indmar_96-06FuelpsiRef.pdf

[electricjohn]

Low rpm problems are at times related to vacuum leaks. Check torques on TB and plenum. Look at your breather in the rocker cover too. Can you still get 5000rpm?

[williemon]

If you have a timing light or spark tester, you should be able to find if a cylinder is missing spark at idle. I  had a similar issue and a timing light showed missing spark. Changed plugs and all was well. 

[Lungo]

@electricjohn Still pulling ~5000rpm without any issues.

 

[justgary]

1 hour ago, Lungo said:

@electricjohn Still pulling ~5000rpm without any issues.

 

You didn't say that you have actually done the tune up that @EchelonMike recommended.  I would definitely include the plug wires in that list since yours are no doubt 18 years old.  They do get old and change resistance.

If the tune up doesn't fix the problem, I would then change the ignition control module (ICM) under the cap.  Use plenty of heat sink paste.  They are temperature sensitive.

[EchelonMike]

On 10/4/2022 at 9:27 AM, justgary said:

You didn't say that you have actually done the tune up that @EchelonMike recommended.  I would definitely include the plug wires in that list since yours are no doubt 18 years old.  They do get old and change resistance.

If the tune up doesn't fix the problem, I would then change the ignition control module (ICM) under the cap.  Use plenty of heat sink paste.  They are temperature sensitive.

Good point on the wires. I ended up finding a set of Quicksilver/Merc plug wires and I am going to swap those this week, when I go down to...I hate this word...winterize. :-) 

[justgary]

1 hour ago, EchelonMike said:

Good point on the wires. I ended up finding a set of Quicksilver/Merc plug wires and I am going to swap those this week, when I go down to...I hate this word...winterize. :-) 

Nice.  Any quality set for a 5.7 SBC should work fine.  Most big box stores have a decent selection.

[Lungo]

Update - I changed the spark plugs but not the wires.  I replaced the cap and rotor as well as the ignition control module.

Now, the boat will either fire right up or crank a long time and then eventually start (sometimes having to pump the throttle in neutral).

There is really no rhyme or reason to it.  It is now winterized at this point so I have all winter to stew on it.

Thoughts on the random starting?  I am thinking I have an occasional fuel pump issue but not really sure.  

I did pull the filter in the fuel block after winterizing to check screen behind it.  It did look like the screen housing was cracked.  Not sure if that would be an issue?

I will want to replace that in spring though and am looking for a part number for this screen and if anyone has replaced this part?  Also the filter part number as well at this point. (Assume this will be similar to any 5.7 engine?)

Let me know what you got.  

Thanks, Brian

[ahopkins22LSV]

I haven’t read the whole thread in complete detail so sorry if this was already suggested. 
 

On my 2013 txi with the 5.7 monsoon I would get random very long cranks and then it would fire. No rhyme or reason either. I chased it for awhile and then on a whim got a new battery. Instantly solved. Might be worth having the battery tested and verifying all connections and grounds. 

[justgary]

1 hour ago, Lungo said:

sometimes having to pump the throttle in neutral

This does absolutely nothing but maybe confuse the ECM on an injected engine.  The only throttle action the ECM recognizes is wide open to set flood clear mode.  Leave the throttle in neutral and crank the engine.

Changing the plug wires is not essential, but they do change resistance as they age.  An intermittent could be a bad wire.  Wires are tune up items, but on a longer term than a cap and rotor.

I also agree with @electricjohn who suggested checking for intake leaks.  Another member here recently found a cracked vacuum hose from the fuel regulator to the throttle body.

[electricjohn]

Some ECM's will enrichen the cranking fuel mixture even more is it reads partial throttle from the TPS.

[Texan32]

As cheap insurance, you really should replace the wires.  As Gary said, at a minimum, they change resistance with age.  Also, your tune-up may have solved part/all of the original issue, but my handing the wires, you could have created a new or exasperated an existing problem with them.

[Woodski]

Prior to putting the boat away, I would perform a leak down test just to satisfy myself that head gaskets are in good shape.  Finding that in the spring rush may lead to long lead time to repair.  Highly unlikely this is the issue, but a cheap validation to avoid a spring surprise.  Long v short crank could be an intermittent crank sensor.

[justgary]

6 minutes ago, Woodski said:

Long v short crank could be an intermittent crank sensor.

I'm pretty sure that a 2004 does not use a crank sensor per se; it uses the distributor pulse to check for engine rotation.

[electricjohn]

Your correct, Gary.