Upgraded Viper running rich?

2015 Viper. 6k miles.

Was built by previous owner at Viper Exchange.
-Prefix race controller
-ARH ceramic coated headers (catless)
-Capristo ACR Valved Exhaust
- Doug Shelby smooth tubes and carbon intake box
-carbon driveshaft
-DSC Tractive Coilovers & controller

So, on cold start, it spits a lot of water, and that water has little black specks in it. The water is probably normal, doesn’t smell like gas, it’s crazy humid here right now, but the black soot in the water makes me think it’s running rich. I also have a lot of deceleration popping, and when I cold start the car starts aggressive. Like the car shakes and it’s loud. I also get possibly a little hanging idle sometimes, if I’m in 1st gear and put the clutch in quickly, only sometimes, it will take a fraction of a second longer for the revs to die down. Idle is a little rough maybe when cold. It holds steady enough at 800rpm with barely any movement in needle but the car will sway a little and I can hear the rpm change just a tiny bit at the same time.

Any suggestions? When I got the car, one of the O2 sensors was unplugged, it was the secondary sensor on the driver side. I figured it had just come undone and I was getting a code so I plugged back in as soon as I got the car home. But, I wonder if it was unplugged on purpose? Would that affect anything?

I’m guessing the best answer is go get a real tune done. Not just rely on the prefix controller. Will prefix adjust the tune on their controller and send back to me? Or is it just one size fits all?

I’m in Minnesota, any suggestions on where to go to get a tune? Nth moto is here but I’d likely need to wait many months from what I hear to get in.

Love to hear thoughts!

All five Gens of our Vipers spit water and some black specs upon cold startup.

As I recall, with the Prefix PCM, they can tune the decel popping either in or out.

Can you go to a local dyno just to establish some baseline info?

Steve-Indy said:

All five Gens of our Vipers spit water and some black specs upon cold startup.

As I recall, with the Prefix PCM, they can tune the decel popping either in or out.

Can you go to a local dyno just to establish some baseline info?

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Yes, I could find a local Dyno I’m sure. I’ve never had a car dyno’d so I assume I’d need to find a Dyno shop that had a wide band so they could see the fueling condition?

The Prefix computer is junk. Go with a stand alone like Motec

Also, shaking on initial start (when cold) is normal. Should smooth out quick though.

The moisture on cold start is normal and is a byproduct of the combustion process. All engines do it. The black spots is most likely the moisture picking up soot in the exhaust system and is not an indicator of running rich.

The decel popping could be how the calibration is done. If the injectors are not turned off on decel it will do the popping. A stock calibration turns off the injectors on a decel.

As far as the shake goes it is an odd fire V10 so it goes with the territory.

Does the car have Cats?

Dan Cragin said:

Does the car have Cats?

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No cats