Viper Miss/Stutter. Wont fire on .02 Gap

[Cable810]

After the first ride of the season I'm left with trying to get the sled running right...

2015 Viper MTX Mpi turbo.

Between 5100 and 6200rpms there's a stutter and sounds like a miss. 0lbs of boost at around 40-45mph i get a constant stutters and sounds like it's missing as well. Once I get into power and 1lbs of boost and up she runs like a raped ape. Left off the throttle to come to a coasting stop I hear a little back fire.

When I'm 5100-6200rpms and it's stuttering/missing Afr is jumping from mid 10s all the way up to 13.5. When I'm into boost afr reads 10 to 10.01. Idle jumps from 10s to mid 12s.

At that point its making me think its a fuel issue or a tunner issue with the gems and its not delivering the fuel properly. I've adjusted the gems have yet to test.

I check the coil packs and they are showing they are good per the ohms I was seeing.

The only 2 things/upgrades i have done to the sled was stage 2 clutch from Schmidt Brothers and finger throttle from munster.

Now having said finger throttle this also has me thinking it could be something to do with that. I went through adjusted per their directions. Have yet to test and see if issue has been resolved.

Tps is showing 0 at close and 0.6v WOT is 99% and 3v or 4v

No codes are thrown for miss.

Now I went through and changed the plugs and I found this a little weird. I set mine to .020 wouldn't fire just crank and crank. I would try to fire but wouldn't. Got it to fire once when i held the throttle slightly but died as soon as i let off. Tried. 030 same thing,.035 same thing again. Set it to .038 per NGK recommendation and it fired no problem. Seems a little odd. I've seen many posts saying to run .020.

Plugs looked good white with a little but of brown. Little lean but not bad.

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Could potentially be a Throttle Saftey Switch issue. Just seen a video on it and I'm thinking that could be the culprit since that's removed after the finger throttle install.

 

[mbarryracing]

When you have a misfire in a cylinder, or cylinders, the unburned air passes into the exhaust and that is why you will see a big fluctuation in the AFR from rich to lean. 10:1 at part throttle is too rich, flooding the motor and probably causing a rich misfire.
I don't think the plug gap was the issue for no start, thik it was a coincidence. I run my plugs on boosted sleds gapped at 0.018" to prevent misfire under big boost. No problems starting. Are you running good fresh fuel? Stale fuel doesn't ignite very good, will cause starting issues and misfires.

 

[Cable810]

I had topped it off with pump 93. Stupid me left the sled empty all summer....

As an update. I replaced th3 inline fuel filter and problem has now moved into Boost.... stutters under 1-3lbs of boost. Sled runs fine when playing, just when we get on trail and cruising is when it does it.

Afr is a little better at 5200 to 5800 rims. Afr isn't reading much when mid range cruising

 

[mbarryracing]

What does a little better mean with the AFR? What is it reading before and during the misfire at cruising part throttle? It sounds like an unhappy fueling transition in the map of the GEMS controller.

 

[Cable810]

Got the idle to get a tad leaner and it's not jumping as much in that 5200 to 5800 rpms.

When it gets into boost(1-3lbs) afr reads 10 and doesn't move.

 

[mbarryracing]

I believe you have a rich misfire, the controller is flogging the motor with too much fuel right where it is transitioning into boost. Too much too soon.
Does your AFR gauge have the ability to read richer than 10:1? You might be actually experiencing 9:1 that is causing the misfire, like throwing on a choke...

 

[Cable810]

The gauge only reads 10 at the lowest point.
I'll mess with the adjustments a little more tomorrow.

I'll pull the plugs again and check them and gap down to .18


I wish MPI would have put RPM values for each Mode. That would make tunning the gems so much easier!

Half tempted to get a PCV and and ditch the gems all together.

 

[mbarryracing]

The GEMS controller is load based, using injector pulse length and boost pressure. I first started out using a similar Dobek piggy back contrtoller on my boosted Apex, had a burble / misfire when it transitioned into boost at 2psi while cruising, the boost fuel was coming on too much. If I romped on it, it passed through that zone so quick it wasn't noticable.
I am not totally familiar with the GEMS program settings but I would start by verifying they are the same as MPI specs. Research and learn as much about how the GEMS program works and how to adjust those different zone settings.

 

[RobX-1]

Half tempted to get a PCV and and ditch the gems all together.

Didn't know if you saw this post by Allen.

 

[Cable810]

The GEMS controller is load based, using injector pulse length and boost pressure. I first started out using a similar Dobek piggy back contrtoller on my boosted Apex, had a burble / misfire when it transitioned into boost at 2psi while cruising, the boost fuel was coming on too much. If I romped on it, it passed through that zone so quick it wasn't noticable.
I am not totally familiar with the GEMS program settings but I would start by verifying they are the same as MPI specs. Research and learn as much about how the GEMS program works and how to adjust those different zone settings.

That's good information to know. This is my first boosted sled so everything is a learning curve.

 

[Dannel94]

Did you find the fault? Having a similar problem.

 

[Cable810]

Did you find the fault? Having a similar problem.

Okay what i have figured out thus far is it is related to the GEMS and EBAC system.

I found that my EBAC was slightly open
Open enough to get moisture in the box. I unplugged it before our UP trip. Ran absolutely awesome the first day we rode. No stutter or miss!!!! Temperature was low 20s. On Saturday she was running awesome first half of the day but as it warmed up throughout the day up in to the lower 40s it started acting up again.

I found out more about my sled with this happening. Ended up finding a invoice number on my Computer for Ulmer. I called him talked to him and he suggested to bump up my Mode 5 on the gems.

I have yet to test this as I'm waiting for my new suspension brackets from CR Racing.

My plugs were also BLACK after this trip. I also want to note that I was forced to run 91 with some octane booster. I typically run 93 at all times but I was forced to run 91. I doubt this had anything to do with my issue as it's been doing this before I ever put 91 in my sled.

I also noticed my fuel consumption on both days was way above normal. I was getting about 50 to 60 miles on 3/4 of a tank. That was running trails to spots we jumped off trail to play.

 

[Cable810]

UPDATE: Stuttering issue has been solved!!! All of my issues I have been dealing with last season have been linked to a bad turbo! The bearings on the turbo went out and cause the exhaust side turbine blades to bend a chip.

New turbo cartridge and she runs amazing! Still some work to do on fueling but she's 100% better running
@Dannel94

 

[Cable810]

Did you find the fault? Having a similar problem.

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