1 engine revs slower than the other

[pwgsx]

Finally after check engine lights and temp issues I got everything fixed for the most part. Now for the last issue that is not resolved that has been happening from day one........Both engines- 155 N/A's start with no problems, both idle at the same rpms in and out of the water, I have adjusted the throttle cables and reset the tps with the candoo and they are almost identical. However if I push both throttles evenly to say to a target of 6000 rpm's, one engine revs to 6000 rpm's without hesitation and the other slowly increases rpm's when it suddenly takes off and stops around 5500rps. No matter where I keep the throttles WOT, halfway or 3000 rps, one engine is always 500 rpms less. Out of the water it is the same, when I start the engines to blast water out after riding, one engine rev's right away, the other putters for a second and then takes off. Since I have 2 engines, I was going to swap the coil packs and see if the symptoms go to the other engine, if not I was going to swap the fuel injectors. Other than that, I will be out of ideas. Help

 

[pwgsx]

Anyone? I searched for 3 hrs and found a few people with the same issue but no solution.

 

[pwgsx]

I cannot find anyone who found a solution to this other than putting more slack in the cable on higher revving engine to match the lower one. For some reason I don't like that solution nor does that help with the lag/bog the slower engine does before it takes off.

 

[Sportster-2001-951C-Stock]

If the motor is running correctly then I vote for adjusting the cable if you want the throttles synchronized!

 

[Sportster-2001-951C-Stock]

"the other putters for a second and then takes off."

I imagine these motors have a MAP sensor, are both reading the same KOEO and KOEI?

What other data do you have, can you watch live injector pulse width or fuel trims and ignition advance using the CANDOO?

 

[devonte007]

I too would focus on trying to solve the bogging/hesitation issue as a first step. Unfortunately I really don't have any suggestions as to how and go about doing that. On the plus side, you have 2 engines and that can make it easier to test and swap parts and sensors in order to nail down the cause. Also you have the candoo which should come in handy.

Let me think about this for a bit and do some research, I'll post back if I can come up with any suggestions that may help. Have you considered swapping the ECU's just to rule it out before digging into all the other individual sensors and electronic parts?

 

[pwgsx]

I never have messed with the Candoo except for clearing /reading codes. My plan of attack is going to be to swap the plug coils and if no change, then the fuel injectors. Other than that, I am not aware of any sensors to swap since the oil and temp sensors are all working. I assume to swap out the ECU's is just unplug the one and plug the other one in? IF that corrects the hesitation then at least I know what its narrowed down to and can attempt to read it with the Candoo.

 

[Sportster-2001-951C-Stock]

Not really sure what the candoo is capable of but I expect you may be able to monitor live engine data as the engine is running and while it's stopped but alive with "key on".

Perhaps you can see dynamic values such as ignition timing advance, injector pulse width, throttle position sensor voltage or position, manifold absolute pressure (vacuum), engine RPM, idle air controller valve position, and a few others.

For example say for instance with key on and engine off port side engine shows a normal reading of 101kPa intake manifold pressure but the starboard engine reads some other value then you can inspect the associated wiring and sensor itself, or when running at idle you should see a sensor pressure of around 30 kPa (~18" vacuum) and if not then there may be a vacuum leak at the sensor connection.

Thus using candoo, you may be able to identify by comparing the various engine sensor feedback values and isolate a potential problem area.

 

[Sportster-2001-951C-Stock]

Same thing might be the case for engine temp sensors as well, if the computer thinks the engine is hotter than it really is then it may not be advancing ignition timing, for example.

 

[Sportster-2001-951C-Stock]

Of course a fresh set of spark plugs also sometimes helps, I bet you've done that already though.

 

[Sportster-2001-951C-Stock]

On the Yamaha's we service, we use an candoo equivilant to do things like commend the MPEM to spark the plugs a couple times a second so we can watch and see if one of the ignition coils is breaking down. We had one a couple weeks ago that had a bad connector in the harness that was not allowing current to pass from the ignition system through the coil intermittently and found if we jiggled the harness the coil began firing the plug. This helped us to isolate the reason for an occasional ignition miss.

 

[pwgsx]

Good info, glad the temps here have dropped to the mid 80's from being 100last week. Looks like I will be spending a lot of time crawling down into the engine area. Yes I did replace the plugs, the issue was the same. I will report back if I find anything or not.

 

[devonte007]

The reason I mentioned switching the ECM as a beginning step to tracking down this problem is because the ECM is at the top of the food chain of things that could possibly be wrong. Since your engine issue does not manifest itself with any engine codes, warnings, etc. you are flying blind. In cases like this I like to approach the testing from a scientific point of view and work my way down from the top. Too many times I have worked my way from the bottom up or from somewhere in the middle and wasted lots of time and effort. In many instances had I worked from the top down in logical manner I would have found my problem much faster and with less effort.

I still have no idea what could be causing the engine issue, but my gut tells me it is something to do with the sensors or electronics. The ECM relies on data from a dozen different sensors to control spark, timing, fuel. If it is getting bad data from one or more sensors then everything gets thrown off. Whatever the issue is, it is so minor that the computer does not recognize it as a fault - and this is what is going to make it difficult to track down. If the issue were mechanical you would probably have more serious engine problems, but it probably would not hurt to verify compression if you have not done so already.

I support what others have told you about using the candoo to monitor all aspects of the engine and using the data to compare it with the good engine in hopes of tracking down the cause of the problem. Hopefully you will be able to spot some sort of inconsistency from the computer link and won't have to do much crawling around the engine.

I also sorted through the shop manual and as far as I can tell you should be able to simply swap the ECM's and they should function properly since they are both already married to your key and dess post. Before doing so, make sure to unhook the battery and discharge any residual electricity. The manual says the ECM's are very sensitive to electrical anomalies.

I wish you the best of luck with this. I am very curious to hear what the problem is once (if) you find it. In the mean time I'll keep thinking on this and let you know if I come up with any other suggestions.

 

[Sportster-2001-951C-Stock]

I agree, there's absolutely nothing wrong with swapping the two MPEM's. I replaced a computer myself recently, it wasn't a Seadoo computer though.

I knew it was bad by watching the sensor feedback, one of the I/O channel values was jumping all over the place while the voltage at the sensor (measured by voltmeter) was steady as a rock and at the correct value.

 

[pwgsx]

That settles it then, 1st is the ECM swap and work from there. IF I have the main battery switch turned to "off" that should be fine right? No need to actually remove the cables from the battery post. From the manual it looks like the 2 plugs on the ECM just pull straight off, is that correct?? Then remove the 4 bolts holding it to the engine.
On a side note- I was looking at the ECM's before it rained last night and the ECM that is on the engine in question has a new barcode sticker over the old stick- looks like it might have been replaced before.

I also thought of swapping the 2 fuse boxes that go to each engine located near the fuel tank, not sure if that would have anything to do with this, but maybe worth a shot??

 

[devonte007]

Interesting about the ECM and that sticker...

I would not waste my time with the fuse boxes or even the MPEM, all they do is divert power where it needs to be. The only thing that actually controls the engine is the ECM.

I think you should be safe just putting the battery switch to off and make sure there is no residual energy in the system by turning something on like the fan.

 

[Sportster-2001-951C-Stock]

If the engine controller isn't programmed with the correct calibration revision, that would create problems for sure.

 

[pwgsx]

Ok, hooked up the candoo........ intake, exhaust and engine temp both read almost identical. Intake pressure read 14.3 on both- not sure if that's right but both engines read the same. Min intake psi were the same, max psi was 1.03 lower on the trouble engine than the good engine. So far none of that raised any flags. Swapped ECU's and no change. Swapped coils on the plugs and no change. I didn't get to the injectors bc I couldn't figure out how to remove the hose going to the fuel rail but I am not holding out much hope. Here is a pic, how does that hose come off the rail? The part circled has some kinda clip on it but no tabs that I could see.

Next would be a fuel pressure test- Don't know where to begin on that.

 

[Sportster-2001-951C-Stock]

That looks like the one you can squeeze the ring and pull off, but that type is usually low pressure. I really don't know on the Seadoo. Most of the high pressure lines have a bolt into a block or the garter spring type you slide a collared tool inside of to release.

Sounds like swapping the engine computer didn't improve running characteristics.

"Min intake psi were the same, max psi was 1.03 lower on the trouble engine than the good engine."

"Intake psi" I guess you mean the sensor that measures intake manifold absolute pressure. "PSI" may imply a positive pressure, which never happens in an N/A motor. But 1psi is a large difference when converted to kPa, it's a difference of 7 kPa

I don't know what the units are on the 14.3 number you gave or if that was while running or stopped, doesn't sound like kPa or inches of mercury vacuum?

 

[Sportster-2001-951C-Stock]

On that fuel fitting, you can probably find out exactly how it's supposed to be removed from the service manual.

 

[devonte007]

The manual is quite vague about how to remove the fuel hose, it says to insert pointed tools each side where the tabs are; that's it.




If the fuel rail swap does not produce results I would next focus on the throttle body, maybe swap those too. With the candoo (from what I could tell of screenshots from their website) there is a tab you can select that shows the engine monitors. One of those monitors is a simulated dial that gives you position of the throttle position sensor 0-100%. When you work the throttle lever by hand does the computer show TPS movement in direct relation? You mentioned the problem is that there is a delay when you move the throttle to when the engine actually spools up. I wonder if the engine computer is getting lazy info from one of the throttle body sensors.

If it is not too much trouble maybe you could post a quick video of what the engine is doing (or sounds like) when you move the throttles, might help us a bit understand what is going on.

 

[pwgsx]

Those #'s were min and max from running last time out. It would make sense to me that one was lower since that one is not revving all the way as the other, hence the 1.03 lower reading.......I would assume anyways. The 14.3 # is all that it showed with the engine off. I was told its atmospheric pressure and that number is correct. I was not able to run the engine, the candoo would not let it start while connected. The TPS #'s both show 0 and move accordingly when the throttle is moved. If I were to swap throttle bodies, does it just unbolt and then unplug any sensor connectors?

 

[Sportster-2001-951C-Stock]

Okay, I was experiencing brain freeze or something. 14.7psi is sea level atmospheric pressure, so you should see near that (in psi units) with engine off key on. That would be about 101kPa, and idle should be somewhere close to 35kPa, which is about 5.1psi, 9.6psi less than atmosphere. 35 kilopascals = 10.3366804 inches of mercury, and atmospheric pressure is about 29" of mercury, so you would have slightly less than 19"Hg of pressure remaining in the intake manifold.

Strange they're using psi units, don't see that often. Maybe b/c they're avoiding confusion for the supercharged motor.

I wouldn't swap throttle bodies unless you suspected something was wrong with it by physical examination, like if the butterfly shaft bushings were worn out or the sensor was giving strange feedback. It's not often throttle bodies themselves wear out but they can become dirty and stick slightly open.

Where is the idle air control valve located, on the throttle body? And I need to look at your earlier post to find manifold vacuum sensor pressure during idling (it's 14.3psi key on engine off).

Yeah, I don't see intake manifold pressure at idle, above just the min value. Funny, I would expect the min value to be lower on the good motor b/c it's running better it should make better vacuum.

If you have a fuel pressure gauge you can connect that to the injector rail and see if fuel pressure is being regulated, also do key off pressure decay check, which can tell you if something's leaking, such as an injector. The fuel rail should hold pressure for a good while, not leak off.

 

[pwgsx]

What kind of fuel gauge do I need? Is it a general type from the auto parts store. The manual shows PN 529035591 Pressure Gauge that's $155. Anyone have one I can borrow? lol

 

[Sportster-2001-951C-Stock]

Go see NAPA autoparts, they might be able to fix you up with the fittings you need to adapt an less expensive automotive gauge.

Or, you could swap the fuel system components over. Are there two electric fuel pumps or just one?