Viper MpI Stutter

[Cable810]

Here we go again....

My viper is back to stuttering.... I can't tell if it's either a fueling issue or a spark issue.

Found two boost leaks and fixed them. Thought that was my over all issue but apparently not... went for a short rip and its still stuttering...

Seems to be typically around 6000 and Up rpms. Pretty much right where it should be getting into boost.

Here is a youtube video when it's stuttering.


Also here is my first post relating to this issue.

https://ty4stroke.com/threads/viper-miss-stutter-wont-fire-on-02-gap.165889/#post-1628005

Had it fixed and ran great but unfortunately ended up back in the same spot...

I got to test the coils,original tune and a new inline fuel filter this morning and nothing changed.. still stuttering right at boost.

Afr Gauge reads 13-15 at low cruising speeds 4800-5500 rpms. Idle is 15-16 with the Original tune and rich(10-11) with the 2nd tune When I punch it the AFR wrapped out to 19-20 and that's where the stuttering is... I believe my rpms are well above 6000 when I punch it.

Clearly the sled is pulling fuel when it's getting loaded up.

Took it to a dealer to have fuel pressure checked and its fine at idle about 50psi I think he said. It was within spec from what he told me. Supposedly my buddy now has a fuel pressure gauge and we are gonna try and see if we can get a reading when it's stuttering to see if there is a dip in pressure.


I'm also in touch with Ulmer

 

[motojunkie101]

How is your o2 sensor? It sounds like it is reading correctly, but they've been known to fail before. AFR of 15-16 sounds normal at idle, 10-11 sounds way too rich. 19-20 under boost is scary lean. If I recall correctly, the target used to be 12-13 under boost with these motors. I would look really hard at the settings in the GEMS controller, they used to be prone to failure at times that would cause all kinds of funky issues so if you can get your hands on another box to test, I would do that. I know my viper had a stutter/burble right as boost would start to build too, but it wasn't bad, just the transition from stock mapping to the box adding fuel.

 

[Cable810]

It ended up being the PC6.... Ulmer sent me a tune that added more fuel at the 7k range which didn't fix it... swapped out the PC6 to the Gems(thankfully I didn't toss it) and problem solved!

Rode last Saturday and Sunday without a hiccup! Have a slight fueling issue at cruising speeds but AFR reads fine so I'm not gonna worry about it. I ride off trail 95% of the time so it's no big deal.

Waiting to hear back from Ulmer for the next step regarding the PC6.