PDA

View Full Version : X7 MCX350 Engine- Pause on initial acceleration.


eurosysytem0
09-20-2011, 11:42 AM
TT Regular

Join Date: Aug 2010
Location: south
Posts: 86
The boat is a 2005 with 110 hrs. It has had new plugs
I have a significant problem with an initial pause when accelerating out of the hole.
I have checked the boat throttle (which I had assumed was mechanical) and it is infact drive by wire.
Can anyone give me info on
a. Location of the throttle position sensor?
b. Is it adjustable?
c. If yes how is it set up to ensure correct position to get "instant" response when hitting the throttle out-of- the-hole
d.Are ther any other adjustable components that can affect intial throttle reponse?

Apart from this intial response problem, the boat appears to be running like a dream (albeit very thirsty compared to my old 240 Prostar.

All help from users/experts appreciated. Any diagrams and or copies of workshop manual pictures/pages would be really appeciated.
Thanks

DooSPX
09-25-2011, 08:20 PM
I had/have this issue with my 91. Given, it's not a EFI engine, but it could relate.
What I have found out, if there is older fuel in the tank, even with Star-Tron, it would have what felt like a pause at the very second you put the throttle down. It's actually a extremely quick sluggishness, about a few milliseconds. With new fuel, its full power on as soon as you touch the throttle.


Does it happen when you have brand new fuel in the tank?

eurosysytem0
10-03-2011, 09:38 AM
Thanks for the input. I have been disappointed in the lack of suggestions so-far from the forum members.
with regard to fue,l I cycle a full tank about every two weekends so age of fuel is not the issue.
Its definitely something to do with injection/timing settings or, as someone suggested the throttle position sensor. With the boat gears disengaged (ie in neutral) I can move the throttle forward to 10 oclock before the engine revs increase. However even then if I push the throttle forard with forward gear engaged and thenpush the throttle hard (drive by wire) out-of -the-hole I still get the pause. Its just like turbo lag on a car.

Anyway thanks again. I apprciate you taking the time to try and help.

CantRepeat
10-03-2011, 09:48 AM
The TPS should be just a bolt on and forget it. I do not believe there is an adjustment for it, the ECM uses the data from it.

Have you check your fuel pressure?

Jerseydave
10-03-2011, 09:50 AM
Perhaps your MC dealer can scan for codes and pinpoint if the TPS is bad. I'm sure there is a way to test it with an ohm meter, but I'm not sure what the procedure would be. JimN on here is a good guy to ask about troubleshooting these kind of problems.

I have the same MCX in my '05 X-star with no stumble or hesitation so something is not quite right with yours for sure. Does it lag with the perfect pass turned off?

As cantrepeat said check fuel pump pressure too.

eurosysytem0
10-05-2011, 09:23 AM
Thanks to JerseyDave and Cantrepeat,
The pause is there with or without perfect pass.
I have not checked fuel pressure. I assume it has to be a dealer check.
Nice to know that your MCX doesnot have the same problem so it does sound fixable.
It seems like the only way I am going to solve this problem is going to a UK MC dealer (I am in the UK) so it probably means mortgaging my house!
regards

CantRepeat
10-05-2011, 09:45 AM
Thanks to JerseyDave and Cantrepeat,
The pause is there with or without perfect pass.
I have not checked fuel pressure. I assume it has to be a dealer check.
Nice to know that your MCX doesnot have the same problem so it does sound fixable.
It seems like the only way I am going to solve this problem is going to a UK MC dealer (I am in the UK) so it probably means mortgaging my house!
regards

There should be a schrader valve on the fuel rail that looks like this.

http://image.truckinweb.com/f/tech/engine/8327533+w200/0708tr_28_z+2006_chevrolet_ssr+schraeder_valve.jpg

You should be able to get a gauge from your local parts store to check the pressure.

atthelake
10-05-2011, 10:31 AM
My 09 star is doing the same thing, I am taking it into the dealer next week for some warranty work and I'll try and remember (write down) the "fix". That may or may not help you, not sure how big of difference there are between those model years.

Gert
10-05-2011, 03:52 PM
Mine does not have a drive by wire, but mine accelerates excellent. I know that does not help you, but since responce is very low, I thought perhaps a little help would be nice.

Going to the dealer is the most easy and expensive step.
It looks more like a ignition hesitate to me, but you never know.
Fuel rail can easily be checked at the schrader valve like mentioned here before. You can buy pressure equipment pretty easily.

Example, this is in the US, but I am sure you can find one cheap in the UK too, like I did over here in Holland:
http://www.ebay.co.uk/itm/FUEL-INJECTION-PUMP-PRESSURE-TESTER-GAUGE-KIT-CASE-NEW-/360398420746?pt=Motors_Automotive_Tools&hash=item53e96b7b0a
This is P&P.

With this you can check fuel pressure, but like I said, I cannot believe this is the problem.
*Edit* Just did read this topic http://www.mastercraft.com/teamtalk/showthread.php?t=41614, and here it is the fuel pump. So get an gauge, connect, drive and look if fuel pressure is stable.

I read you changed plugs. What about plugwires and rotor? Is there another MCX around in your place so you can swap some items? On the other hand, again, only with this low hours, naaah don't think so.

So, you keep other sensors to check. Ignition is coming from igniter, this is receiving the signal from the ECU which is feed by many sensors, like crankposition, tempsensor, knock sensor en tps.
From here I don't know if the MCX is equipped with a cam sensor too? Anyone? I could take a look at my MCX, but she is not around at the moment.

So, I suspect it is one of the sensors. Maybe you can remove the airfilter, and look if the throttle valve does close visually under acceleration. If not, problem should be somewhere else.

Like I said, is there a way to swap parts with an other MCX around? That is the most easy way.