2007 GTX 155 RPM issues

[Kpvalentine]

Hello I am new to the forum! I am having an issue with one of my GTX wakes. It will only go up to 6400 RPM's WOT. Here is what I have tried. Changed spark plugs, fuel pump and filters, swapped coil packs with the other one that runs fine, ran it with the seats off, checked throttle travel, checked oil lvl, checked compression on cylinders - 162, 165, 178. When I take it out it runs at 5800rpms then after a few minutes will increase rpm to 6400. It also misfires at 3500rpms sounds like popping out of the exhaust. Is that compression ok? any other ideas?

 

[ski-d00]

Compression is fine. I have seen rpm issues like yours a few times. Once it was a pump issue where the impeller was badly bent not letting it rev up in the water and another was a voltage issue and another was an ECU issue. If I could here it run I could probably pinpoint the problem easier. Maybe post a quick video if possible?

Since you have 2 identical skis, you can swap parts from one to the other. First, I would switch ECUs since it is a 5 minute job. Just take the 4 screws out of the good one and plug it in the bad ski. You don't have to remove the bad one just let it sit on top of it and you can zip tie it down so it doesn't bounce around if you take it out for a test run. If that checks okay, I'd swap rectifiers since it is also easy, then I'd switch jet pumps which is a little more work but will rule out a lot.

 

[Kpvalentine]

here is a link to the video of running it at 3500 rpms this will give you an idea of the noise im hearing. I am going to start with the ECU, then rectifier. Both of them are new to this ski!

 

[ski-d00]

The ECU is new to the ski? Is that when the problem started? Are you sure it is the correct ECU?

 

[Kpvalentine]

SOLVED! Ok so I switched out ECU's. Ski 1 (the working ski) had the original ECU that came with it. Ski 2 (problem ski) ECU died and I got a used one that was a newer generation which required a different generation MAPS. When I swapped out the ECU from ski 1 into ski 2 I had to unplug the MAPS . when I tested on the lake it immediately had full RPMs. Ran perfectly! The problem all along has been a faulty or incorrect MAPS.

I am ordering the correct MAPS. THANKS for the help ski-d00! without swapping out the ECU I would have been searching for a while. I have learned a lot at least!

 

[ski-d00]

When I swapped out the ECU from ski 1 into ski 2 I had to unplug the MAPS .

Manifold Air Pressure Sensor?

 

[Kpvalentine]

yep that's the one! I glad it was something simple and I didn't need to tear the engine or anything else apart.....

 

[ski-d00]

I'm really confused. Pretty sure all MAPS for the 4tecs were the same? Or at least interchangeable as I know that Bosch had a couple different part numbers and label colors. And why were you unplugging it? It is down almost on the side of the intake manifold.

 

[Kpvalentine]

From what I researched and heard there were three different generations of MAP sensors paired with ECU's from different years. Now this could be hearsay but I was speaking to people who have been around skis a lot longer than I have.

As far as getting to the sensor its not hard to reach in and get to it. I actually did it while on the ski to test it because I've had a problem with it throwing a code and unplugging to test it before.

I do stand corrected BTW. It is not a MAP sensor issue its an ECU issue. I tried two different MAP Sensors and got the same problem. I am sending it back from where I got it and they are replacing it for me.

thanks so much for all your help. This community is pretty awesome!

 

[ski-d00]

Just checked, all the part numbers of the MAPS are interchangeable for all years 4tecs so maybe they were referring to another sensor like the OPS which I know changed from normally open to normally closed type around 2009.

If you would have mentioned that your speedo wasn't working it would have helped diagnose the bad ECU. The Siemens ECUs can have accessories just stop working like speedo, fuel level, etc. which point to bad ECU. I've tried to reflash ECUs with these issues and it doesn't work. They are toast.

 

[Kpvalentine]

that is good to know on the MAPS thing. Thanks for clarifying. I didn't realize the speedo not working was an ECU thing. I figured it was an electrical or mechanical issue somewhere. next time I will list all the issues I'm having as you are right it would have made diagnosis a lot quicker and easier.