2004 Sportster 4tec cutting out randomly

[gravis18]

Have a 2004 new to me sportster with the 155hp 4tec engine. It was working fine most of the day but this was my first time out in it and seems like the rpm surges when you aren't even touching the throttle lever. I made a video on it and you can see and hear the engine cut out and catch itself and then also cuts off completely and you are able to restart it like nothing happened.

Anyone have any idea what it could be? I'm about to replace the fuel filters in tank and double check the fuel injectors but so far no codes or check engine lights. Also have new spark plugs ordered and on the way.

The part where it starts cutting out is between 5min and 7min mark on the video

[video]

 

[MacSeaDoo]

Hey, I was watching your videos this week and was wondering if you would show up here.

Here is my advice:

1.. Check your DESS Post wiring and operation. I say this because listening to your video, when it cuts out you immediately get the key on double chirp. Do you have another key? The post has a magnetic reed switch and if faulty it will cut for a split second.
2.. Check your grounds. Like the above, if the ECU loses the ground, it will reset and you will get the key on beeps. Their are multiple grounds. Make sure they are clean and tight.
3.. Check the battery terminals. Same as above.
4.. I change the plugs each season. They are cheap and at least you will start each season on a level paying field with them.

I can't stress how valuable CanDoo Software is in these situations as if it doesn't help you point out what the issue is, it will at least help you eliminate what it is not.

Love the videos...

 

[gravis18]

Thanks for the response!

1. I did check the dess post and checked the resistance of the post and key with a multimeter with some info I found and everything seemed ok.
2. As for the grounds I checked the 3 ground on the front of the engine block which looked fine but I cleaned them anyway.
3. Also checked and cleaned the wires going to the battery and those looked fine before cleaning as well.
4. I have plugs, both fuel filters, and a tool to check, pulse, and clean the fuel injectors on the way and change the oil so im going to get those basic maintenance items out of the way to eliminate those factors.

As for the candoo pro ive been looking at getting it for sure but this isn't throwing a check engine light so im not sure it would even help in this particular issue or is there something it could show with no CEL being thrown?

A couple things to note is prior to this I did find some water and a bit of corrosion on the MPEM/fuse box under the console which I had to clean and put dielectric grease on so maybe a bit more cleaning might be needed here cause this was causing my bad ground issue before causing the boat not to start

Another thing I noticed was that the gas cap worked its way loose (i dont have the tool to tighten it) it wasn't completely off but was backed off a couple turns exposing the o ring so im not sure if possibly some water could have entered the fuel?

 

[MacSeaDoo]

I had the same problem with water in the console. I solved it by caulking the console to the housing so that if I took a wave of splash it wouldn't just pour in . I also put a better gasket in the bin that goes in the hole.

Hard to tell with the Gas. From what I have learned over the years, almost always a complete engine cutout is electrical. Again, even more so when you do not get a check engine.

I know the Candoo is expensive. I bought it because it gives me more information which helps to speed up the troubleshooting.

An example, is when the Candoo is hooked up and it looses comm when the engine quits, you know the ECU is loosing power.

 

[thehag1968]

im having the same problem , id love some advice