SC Apex Stutter issue

[Yamamauler]

Looking for some idea's and help tracking down a stutter issue on my Apex.
The sled is a 2007 MPI stage 1 Apex with under tunnel exhaust.

After warming up the sled and heading out the sled runs great, once the motor starts pulling hard around 8,000 or higher then the slowing down I get a bad stutter from 2,600 - 5,000 rpm's and generally runs like crap. Stop and the sled will not idle.
Hit the kill switch or turn the off and restart the sled and it runs great until it starts pulling hard or hitting around 8,000 then above issue repeats.
Before re-setting it feels like it's running rich, no adjustments to the fuel controler make a differance at this point but the problem clears up over 6,100 rpm.

No matter what is changed or adjusted the same issue arises. Changed box's (actually tried 3 differant fuel controllers) traced wiring looking for a chaffing, checked vaccum with a gauge and there doesnt seem to be any leaks.
The sled ran great last year and early winter, the only change was the addition of a gunnar tether. I read about guys having issues so I checked and found mine had shorted, I thought this was the issue but the sled is wired back to stock without a tether now (I am going to put one back on after fixing the stutter issue).
No codes flash, nothing else seems to be out of the ordinary.

Any ideas would be appreciated, heading to Revy next week.

Thanks,
Y

 

[apex jeff]

At this point I would remove fuel module from tank, and then inspect for gel or other matter sucking up to pickup screen. Have seen several season to season stability problems with race fuel blends. Just an idea!

 

[347strokin]

A quick and easy thing to rule out is to test your TPS. Just don't forget to plug your factory computer back in first. PM if you need instructions.

 

[Yamamauler]

Thanks, checking these this morning.

Y

 

[Yamamauler]

No luck so far, I'm getting gray hair and missed out on one of the best days of the year.

Y

 

[robrstopr]

Do you have an AFR gage? The fuel controllers for the SC suck. If you don't have an air leak, and your TPS is good....then its gotta be your leaning out more than likely at that RPM.

There is no way to have a great running SC without an AFR gage. Its hit and miss without it.

If you have an AFR gage, I'd take the intercooler out and re install to ensure no air leak. Could be the slightest air betting by under high boost.

 

[robrstopr]

One last note. When mine acts up...which is every ride, its usually the red/blue altitude compensator setting. That and the idle circuit green are the major issues I have.

Have you added Boost Fuel. Green/Blue. Maybe your starving for fuel under load.

AFR gage is a must, but still thinking air leak.

 

[Yamamauler]

Yep, I have an AF gauge and keep a close eye on it.
I still thinkits electicle due to re-setting when turning the key off or hitting the kill button.
I sent my controller back to MPI to check it but I don't think it's the problem as I tried other boxs with same result.
Count down to Revy - 6 days.

Y

 

[WakeGD]

Simple question.

Have you put your sled in a heated shop with a fan to circulate air and let it dry out real good? Then put dielectric grease in all the electrical connections?

I just had MPI test my box this week and it was bad. Their service was fanatastic compared to prior experiences and my sled is already up and running again.

G/L

 

[robrstopr]

I just got my box back from MPI yesterday. Second season in a row I had to send it back this time of season. My box was completely dead both years. Mike was awesome and got it back to life and reprogramed it.

Aparently the slightest moisture sets these things in a frenzy. I don't know, but this is my second new box, and my second season this one had to be cleaned up and reprogramed while I sit home.

Next season I'm going RB3 and keeping this box as a back up.

Your TPS checked out...

Weird.. Good Luck.

You'd think someone on here would have something for an idea.

 

[Yamamauler]

Thanks for the tips, I am going to re-test the TPS tonight.
I am also going to hook the TORS back up and see how it works with and without a fuel controler (I have a spare).
Going to add die electric grease as an SOP from this point forward.

Messed with the sled a little saturday nite after a great ride in 2-3 of fresh on my son's MM 750, had a blast and cleared my mind...LOL

WakeGD,
Yep, sled is stored in a heated shop, I turn a fan on the sled for a day or two after every ride.

Keepin on - keepin on, something will show up sooner or later.

I am hoping to have my box back from MPI Tuesday for the final test relating to the box.

Y

 

[Yamamauler]

Problem fixed thanks to Curt & Justin at FASTRAX and MPI.

Looks like this was a combination of issues.
All wireing traced and checked without any issues, no codes ever popped up.

We were pull what little hair out that was left when we decided to replace the air intake sensor and remove the tether (already removed the Gunnar and replaced it). I sent the MPI Fuel box in to check for any issues, it checked out ok and arrived back wednesday afternoon. My son signed for the package and ran it down to my office then I took it FASTRAX. Curt hooked it up, toasted a belt putting a load on the motor but it was well worth it, the sled seemed fine.
Curt wanted to clean the clutchs and do a little more testing thursday morning, I picked the sled up about 1 pm and headed for Revy.
It took about 5 minutes to tune the box in Friday morning and was good the rest of the trip.
Not sure if its my imagination or not but I think I picked up mileage. I ran the crap out the sled and used less fuel than an M1000 with a pipe.

Thanks for the tips.
Y