MCX Trouble Shooting

sledskiing · Dec 16, 2008

Need some help here.

I have an Nytro MTX with and MCX turbo. Sled ran flawlessly last season. Added a bunch of goodies over the summer and it seems i got some electrical issues. Sometimes the sled runs fine and some times it runs like the MCX box is unplugged. Here is what i've tried

- Dielectric grease in various different connection.
- Red Power wire is fine
- Black ground is fine
- Yellow wire on brake side is fine
- Orange (i think it's orange) on throttle side is fine
- Blue and Brown are not connect - Running a manual boost controller
- Red and Black (that go into the back of the intercooler) wire are fine up to the black connection plug

I have not pulled the intercooler yet.

No air leaks

What else?

At the start of the day the sled runs fine for about 45 minutes and than it starts acting up. When it's not running well here is what happens.

At 1/4 throttle it makes 4-6 lbs of boost than completely dies, no power, sputter. MY AF goes WAY lean. I let off on the throttle or flare it and the AF goes back to normal. When the sled is running fine the AF is normal. When it starts acting up it is completely unpredictable... on and off.

Any help would be great. You can only check / wiggle wires so much before you start loosing your mind.

Ohh I've also tried securing the wire plug into the MCX box better and that only seemed to work for 5 min.

Help

noob · Dec 16, 2008

does it only make 4-6 pds of boost all day even when working well?? wondering if you have bad injectors?? or I know you said you wiggled the wires in the mcx plug in adaptor, but if the red wire aint' making contact it sounds almost exactly like what was happening with mine. basically without power to the mxc box, it cuts off at around that boost you stated. I'm guessing one of those two. anyone else chime in here.

snowy1 · Dec 16, 2008

it sounds like you are not getting fuel to the mcx injectors, could be the box is bad, or a leak, have you done a pressure test. I had to pressure test mine and spray everything with soapy water to find the leaks.

sledskiing · Dec 16, 2008

noob said:
does it only make 4-6 pds of boost all day even when working well?? wondering if you have bad injectors??

The sled is set at 8-9lbs right now. When it's running right it makes 8-9 lbs. That would leave me to believe the injectors are fine

I think

I've tested the red power wire a number of times and can't find anything wrong

sledskiing · Dec 16, 2008

snowy1 said:
it sounds like you are not getting fuel to the mcx injectors, could be the box is bad, or a leak, have you done a pressure test. I had to pressure test mine and spray everything with soapy water to find the leaks.

If the box is bad would it just not work?

No I have not done a pressure test. How do i do a pressure test ..:face-icon-small-con

snowy1 · Dec 17, 2008

the box must be good if its working some of the time. it sounds like you are losing the signal to the injectors for some reason either bad wire or leak not allowing the box to see the boost. you need to pressurize the system. I made a plug that fit in the hose to the innercooler and tapped it for an air fitting and pressurized the system that way, be sure you only put about 20 psi to the system you will need a regulator. it will leak by any of the intake or exhaust valves that are open but as long as you regulate it at 20 psi and maintain the pressure you can check for leaks on all the vacumn lines. make sure no kinks in the vacumn line to the box, and obstructions in any of the lines, I had ice biuld up in them and do the same thing.

robertyoke · Dec 17, 2008

i would take a look at the connectors at the box and see if the crimp fittings are broken. cut that little zip tie that bundles the wires and gently tug on the wires one at a time. mine had two that were broken and it was doing the same thing.

Thistledoo · Dec 17, 2008

Did you leave the electronic boost controler plugged in and tucked away?? I have read that you cant just remove it and put on a manual boost controller.

SPOOLED · Dec 17, 2008

verify that the fuel pressure is good its possibe that the pump has **** the bed but make sure to check the fuel pressure after the the lean condition starts its possibe the pump gets hot after a while, just a sugesstion

Washy · Dec 17, 2008

Thistledoo said:
Did you leave the electronic boost controler plugged in and tucked away?? I have read that you cant just remove it and put on a manual boost controller.

This is what I have been told aswell. You have to leave it plugged in.

APEXXPRESS · Dec 17, 2008

This is not ture .Erik @ MC-XPRESS tells me you can run with out TCV not hooked up.Tcv valve is only controlled by boost map in the EFI box.
I agree, ck for air leak or wire pin connection on type 3 box.
Mark

sledheadd · Dec 17, 2008

I am doing a boost control valve and I am what is where is this electronic boost controller and should I disconnect it?

drinkwyo · Dec 17, 2008

i would start by pulling the fuel tank and checking the vacume lines very well. i had one of the plastic t,s break and it ran like chit. replaced the t and all was good.

sledskiing · Dec 17, 2008

i'm gonna pul the intercooler tonight to make sure nothing is going on with those 2 wires.

I didn't see any pinched tubes or air leaks. I doubt there is an air leak but ya never know.

Keep the ideas coming

Washy · Dec 17, 2008

There is a way to check the injectors. Remove the intercooler, plug the line from the throttle bodies so the sled will run. You can pump up the boost sensing line to the MCX control box to 10 psi with a hand pump and see if the injectors will fire. We did this to a phazer once and it worked.

There may be more involved than this though.

sledskiing · Dec 17, 2008

OK pulled the 2 allen bolts off the intercooler and the RED and BLACK wires look fine. All the air lines look OK.

So if one of the lines is freezing would the sled be doing what I am describing?

SPOOLED · Dec 17, 2008

sledskiing said:
OK pulled the 2 allen bolts off the intercooler and the RED and BLACK wires look fine. All the air lines look OK.

So if one of the lines is freezing would the sled be doing what I am describing?

nothing like that will freeze they are just vac and pressure lines as well as fuel nothing to freeze and would not cause that condition, check the fuel pressure .

snowy1 · Dec 18, 2008

SPOOLED said:
nothing like that will freeze they are just vac and pressure lines as well as fuel nothing to freeze and would not cause that condition, check the fuel pressure .

if you get moister in those vacumn lines they will freeze and cause that problem, I know from first hand experience. and they do seem to get alot of moister for some reason atleast mine did. I think its due to the filter location and pulling in steam from the exhaust. I had ice in my vacumn lines and in the mcx box, and I know others had the same problem. I agree its not getting fuel but it could be a fuel pressure problem or a vacumn line problem if the pressure can not get to the mcx box it will not see the boost and will not add fuel.

SLY · Dec 18, 2008

The heat from the exhaust and the screen filter is a great recipe for moisture ingestion. Had lot's of experience with that. Snorkel and K&N will help but the moisture will get into the system and cause problems. Make sure the hose to the MCX box is not running downhill as moisture getting into the box will mess it up. Ice forming in the air filter overnight can also break off and damage the turbo so pointing the exhaust away from the air filter will also help. Any vacuum/pressure leak will make it run bad.

noob · Dec 18, 2008

where is your mxc box located?? heard guys having issues where the instructions say to place it, put mine above the intercooler instead of on the side by the battery mount. another option to check out.

MCX Trouble Shooting

Well-known member

Well-known member

Well-known member

Active member

Active member

Well-known member

Well-known member

Active member

Active member

Well-known member

Similar threads