Idle speed, acceleration, & top end issue

[mkov608]

Sea-Doo mechanics, I need your help.

I recently purchased a pair of 2002 GTX 4-tecs. Both skis had 43 hours, both have new batteries, and were recently serviced by a dealer in AZ. Ski 1 is in perfect shape with no problems; it’s a screamer! Ski 2 is a different story.

The main issue is that ski 2 only hits about 6400 RMP, while ski 1 hits 7200+. As you might expect, there is a difference in top end speed, and ski 1 jumps out of the hole much more aggressively. There is also an idle speed difference between the 2 skis. Ski 1 idles at about 2000, and ski 2 idles at 1600-1700. According the on-line Sea-Doo manual, the ECU sets the idle speed, so I’m not sure how to fix that problem.

I’ve also inspected the jet pumps and drive shafts. On ski 1, everything looks good, but on ski 2, there is a ¼ gap between the end of the drive shaft and the impeller. I’m not sure if this is a problem.

Ski 2 maintenance to date:
1. Replaced throttle cable, and reset TPS w/ Candoo
2. Fresh spark plugs
3. New battery
4. Sea-Foamed engine, and added 1 can of Seafoam engine treatment to gas tank. The skis were sitting for a while, but I’ve already run a tank of gas through it.
5. New information center (old one had significant corrosion on elect connections inside and kept setting faults)
6. Compression ck: Cyl 1= 190, Cyl 2=195, Cyl 3=195
7. Fuel pump pressure ck = 44 psi.
8. Jet pump wear ring inspection; impeller looks great, gap is within tolerance.

At this point I’m leaning toward the throttle body, the jet pump (binding) or both.
If you have fixed a similar problem, or you have other suggestion for things I should check. I’d really appreciate your input.

Thanks!

Mark

 

[ski-d00]

sounds like a pump/impeller problem, try switching the complete pumps from ski 1 to ski 2 and try them both out. that will tell you if it is the pump or not.

 

[mkov608]

Excellent suggestion. Now I have another question for you. When I look at the candoo scans for each ski, ski one TPS shows 8-9 and ski 2 shows 6-7. This is probably why ski 2 idles at a lower RPM than ski 1, but how do you fix that?

 

[ski-d00]

You can't, regardless of the degree of opening, it's regulated by the ECU at 1800 rpms give or take a little. You can reset the 0 degree position that is slightly off 0 but it won't help, I've tried it. I've found lcd gauges that didn't read rpms very accurately, meaning one gauge was a couple hundred rpm off from the other on the same motor. You can also switch LCD gauges in about 5 minutes. That's the beauty of having two identical skis. It's a part swapping heaven!! Not that I condone it, but for the average person it comes in handy.

 

[mkov608]

sounds like a pump/impeller problem, try switching the complete pumps from ski 1 to ski 2 and try them both out. that will tell you if it is the pump or not.

Ski-doo, I pulled both jet pumps, and they look remarkably similar. No damage and wear ring tolerances is identical. Both impellers spin freely. I did not notice any difference after running both skis.

So, today, I thought I’d swap out all the ignition coils. Again there was no change. Next, I swapped out the fuel rails/injectors. Again, there was no change. So, I pulled the throttle body. The thing looks like brand new; so I reinstalled it.

The one interesting thing I did find is that there is an exhaust leak on the slower ski right where the pipe meets the exhaust manifold. Could that be my problem?

K

 

[red2blue]

.... there is an exhaust leak on the slower ski right where the pipe meets the exhaust manifold. Could that be my problem?

could be...what does the bell look like on the manifold?

How about the J-pipe?...any tell tale marks on the side of the engine compartment of heat?....exhaust leak?

If an intake is drawing exhaust gases...loss of performance is not unheard of.

 

[mkov608]

There is soot on the manifold and the pipe.

 

[red2blue]

un-do the bungie on the water box....remove the v-clamp conecting j-pipe and manifold.

slide water box back a coupla inches...now...check the end of the J-pipe and manifold.

...........


sooty deposits usually mean exhaust leak

 

[mkov608]

Exhaust Leak



Red2Blue, I pulled the pipe, and it's leaking as you can see from the first picture. The flange on the exhaust manifold looks good. If I pour water into the top of the pipe (second picture) between the inner pipe and the flange, the water comes right out of the pipe (see third picture). Do you know where I can get the pipe repaired, or will I have to get a new one?

 

[Coastiejoe]

The fact that the TPS have different readings seems like a red flag to me.

I'd swap the MPEM's and re-read things. See if the numbers move with the MPEM or remain on the ski.

I'm not saying the exhaust isn't an issue, just thinking there is something to the TPS reading..

 

[ski-d00]

the pipe can be welded but you'll need a good welder who can weld stainless and the outer shroud will have to ground off and then welded back on but one leak seems to lead to another. the problem is most likely the exhaust leak which will cause poor performance. I wouldn't worry about the TPS having different readings, it's pretty common and the ECU (not the MPEM) does what it has to do to the throttle to control the idle speed. for example, when a plug fouls, it pushes the throttle further open to try to maintain idle speed.

I have a used 2002 freshwater j-pipe for $75 + ship if you're interested or you can get one off ebay but I wouldn't buy one from FL or another saltwater local because the saltwater eats them up.

 

[mkov608]

That's what I've read as well ... the ECU controls the idle speed. If I'm not mistaken, if I move the MPEM from one ski to the other, I'd also have to move the ECU.

Convenient that you just happen to be parting out an '02 4-tec. Once the pipe arrives and I run it, I'll let you know the results. Thanks Jeff.

 

[ski-d00]

There is no point in moving the MPEM, it is just a fuse box and distribution center. You can swap the ECUs easy enough.

Yes, convenient, but I'm also parting out like 20 other skis as well. I'll ship the j-pipe today.