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Misfire after Unitronic Stage 2 IS20

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New member
Location
Whitby, ON
I upgraded to a KN drop-in filter and an inlet elbow before my stage 1+ tune and my following misfires. I don't think you will solve your misfires & EPC just by changing your inlet elbow, but it could still be a fair upgrade considering you already have an IS20 and an upgraded intercooler, and even if you downgrade to IS12.
With just a drop-in filter (KN, Afe, AEM, etc) to your OEM box and an elbow, you will have more than enough flow for your IS20 tune (and even if IS38). No need for a complete intake!

As I mentioned, I was having the same misfires and EPC light happening at the same time as you described (it doesn't mean it could be the same cause).
Even though Uni says OEM plugs and gap, I adjusted my OEM plugs following APR's recommendation for their tune: "APR recommends properly gapping the factory spark plugs to a tighter gap (Ex: 0.024" ±0.002" or 0.6mm ±0.05mm), properly installed and torqued (Ex: Per the manufacturer's specifications), and maintained with a shorter changer interval (Ex: 10,000-15,000 mi or 16,000-24,000 km)."
And use a proper tool when gapping, do not tap the plug on a flat surface to lower the gap. I gapped mine after watching this video from APR posted in 2015:
Together with the plugs, I changed the coils to APR's, which promises a bit more energy than OEM, with only a few more bucks. At the same time, I had my fuel system + intake cleaned.
After I followed the above, zero misfires or EPC light, all excellent. I'm not saying this will solve your problem, just sharing how this solved mine.

Regarding your PCV, when it is bad to a point to cause misfires, it is usually also making noises, rough idle, leaking oil and showing other codes. And your car is still "young" for a PCV issue. I don't think it is your PCV causing misfires.
Did you change your coils?
 

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New member
Location
Whitby, ON
You also mentioned earlier you are using the diverter valve that came with your (used?) IS20.
I think it worth buying the latest DV revision. I changed mine and noticed improvements, of course, maybe the one that came with my used IS20 was not 100%.
 

jeffdemara

Passed Driver's Ed
Location
Vancouver, BC
You also mentioned earlier you are using the diverter valve that came with your (used?) IS20.
I think it worth buying the latest DV revision. I changed mine and noticed improvements, of course, maybe the one that came with my used IS20 was not 100%.
Tried swapping that. No change. The one that came with my is20 is the latest revision, and only had 70 miles on it.
 

jeffdemara

Passed Driver's Ed
Location
Vancouver, BC
I upgraded to a KN drop-in filter and an inlet elbow before my stage 1+ tune and my following misfires. I don't think you will solve your misfires & EPC just by changing your inlet elbow, but it could still be a fair upgrade considering you already have an IS20 and an upgraded intercooler, and even if you downgrade to IS12.
With just a drop-in filter (KN, Afe, AEM, etc) to your OEM box and an elbow, you will have more than enough flow for your IS20 tune (and even if IS38). No need for a complete intake!

As I mentioned, I was having the same misfires and EPC light happening at the same time as you described (it doesn't mean it could be the same cause).
Even though Uni says OEM plugs and gap, I adjusted my OEM plugs following APR's recommendation for their tune: "APR recommends properly gapping the factory spark plugs to a tighter gap (Ex: 0.024" ±0.002" or 0.6mm ±0.05mm), properly installed and torqued (Ex: Per the manufacturer's specifications), and maintained with a shorter changer interval (Ex: 10,000-15,000 mi or 16,000-24,000 km)."
And use a proper tool when gapping, do not tap the plug on a flat surface to lower the gap. I gapped mine after watching this video from APR posted in 2015:
Together with the plugs, I changed the coils to APR's, which promises a bit more energy than OEM, with only a few more bucks. At the same time, I had my fuel system + intake cleaned.
After I followed the above, zero misfires or EPC light, all excellent. I'm not saying this will solve your problem, just sharing how this solved mine.

Regarding your PCV, when it is bad to a point to cause misfires, it is usually also making noises, rough idle, leaking oil and showing other codes. And your car is still "young" for a PCV issue. I don't think it is your PCV causing misfires.
Did you change your coils?
Tried a set of new coils, no change.
 

victorofhavoc

Autocross Newbie
Location
Kansas City
Why not just try what uni is saying to try? Pcv can cause boost leak, but if that was the case you'd be blowing oil and blue smoke quite a bit. How's your oil level?

So thinking this through, when you shift (6mt and lifting on shift I presume), the dv should dump to some extent as the fueling is pulled, so if it's misfiring then is the dv dumping? If not, or if the line is blocked/choked, it could be going too lean and knocking enough to trip cylinder deactivation? Maybe step back and instead of trying to diagnose the issue with parts/changes either reverse your changes one at a time (within reason) or try to get more logs/data around the specific conditions/environment in which it misfires? You're already kind of going down that path, but I think you may need more data/recreation.
 

jeffdemara

Passed Driver's Ed
Location
Vancouver, BC
Why not just try what uni is saying to try? Pcv can cause boost leak, but if that was the case you'd be blowing oil and blue smoke quite a bit. How's your oil level?

So thinking this through, when you shift (6mt and lifting on shift I presume), the dv should dump to some extent as the fueling is pulled, so if it's misfiring then is the dv dumping? If not, or if the line is blocked/choked, it could be going too lean and knocking enough to trip cylinder deactivation? Maybe step back and instead of trying to diagnose the issue with parts/changes either reverse your changes one at a time (within reason) or try to get more logs/data around the specific conditions/environment in which it misfires? You're already kind of going down that path, but I think you may need more data/recreation.
Thanks for the input! I will be trying what Uni is suggesting of course. I have also tried a different (and known working) DV, but it made no change.

Only things that were changed were:
1. Swap out stock IS12 for an IS20 (that is in perfect shape, and has 70 miles on it). Came with everything on it.
2. Turbo muffler delete installed on the IS20
3. Flashed from a working (no issues) “Stage 2” tune to the “Stage 2 IS20” tune
4. Encountered this problem

So after I encountered this misfire problem, I went out and bought new OEM plugs, gapped them to 0.24”, and torqued to spec.
No change

Tried adding some E, to get to an E20 fuel mixture.
No change

Confirmed “Charge air pressure control valve uncond voltage sensor” is at 3.650v when engine is running.
No change.

Slightly adjusted wastegate rod, ran adaptation, then confirmed voltage is still within range at 3.5596v.
No change.

Then tried RS3 coils.
No change

Tried my working DV from my IS12 turbo.
No change
 

jimlloyd40

Autocross Champion
Location
Phoenix
Car(s)
2018 SE DSG
Thanks for the input! I will be trying what Uni is suggesting of course. I have also tried a different (and known working) DV, but it made no change.

Only things that were changed were:
1. Swap out stock IS12 for an IS20 (that is in perfect shape, and has 70 miles on it). Came with everything on it.
2. Turbo muffler delete installed on the IS20
3. Flashed from a working (no issues) “Stage 2” tune to the “Stage 2 IS20” tune
4. Encountered this problem

So after I encountered this misfire problem, I went out and bought new OEM plugs, gapped them to 0.24”, and torqued to spec.
No change

Tried adding some E, to get to an E20 fuel mixture.
No change

Confirmed “Charge air pressure control valve uncond voltage sensor” is at 3.650v when engine is running.
No change.

Slightly adjusted wastegate rod, ran adaptation, then confirmed voltage is still within range at 3.5596v.
No change.

Then tried RS3 coils.
No change

Tried my working DV from my IS12 turbo.
No change
I would do what they suggested and then when there's no change you can tell them that it's their tune.
 

jeffdemara

Passed Driver's Ed
Location
Vancouver, BC
Well I have TIP now, and from the log I can see it slightly helped WG duty cycle on shift, but EPC light and misfire still happened.

I’ll be getting the intake on Monday and will let you all know when it doesn’t fix it..... LOL
 

tigeo

Autocross Champion
Tried a set of new coils, no change.
It's got to be software strangeness with that auto on your particularly car
Well I have TIP now, and from the log I can see it slightly helped WG duty cycle on shift, but EPC light and misfire still happened.

I’ll be getting the intake on Monday and will let you all know when it doesn’t fix it..... LOL
Wayment. That WG number should be 2.1 or so on/not running and lower setting at 3.6ish on/not running.

What do you get for these 2 on/not running?

Screenshot_20210305-235406_OBDeleven.jpg
 

StorableComa

Autocross Champion
Location
Long Beach, USA
Car(s)
17 GSW S
Well I have TIP now, and from the log I can see it slightly helped WG duty cycle on shift, but EPC light and misfire still happened.

I’ll be getting the intake on Monday and will let you all know when it doesn’t fix it..... LOL
I still vote snow guard removal and a aFe or K&N high flow drop in. Could also do a wider pipe off the airbox too.
 

jeffdemara

Passed Driver's Ed
Location
Vancouver, BC
It's got to be software strangeness with that auto on your particularly car
Wayment. That WG number should be 2.1 or so on/not running and lower setting at 3.6ish on/not running.

What do you get for these 2 on/not running?

View attachment 205432
I know exactly what you mean. And that is all confirmed set correctly. It also passes acknowledgement. And as per everything I’ve read, is set correctly, including having 9 threads showing.
 

jeffdemara

Passed Driver's Ed
Location
Vancouver, BC
So an upgraded AFE drop in filter and silicone hose to feed the turbo inlet made no difference as well. Snow grate has already been removed as well.

still EPC light for misfire under boost when shifting

it must be either something with the way the transmission handles things, or the Stage 2 IS20 tune itself isn’t playing nice with my car for whatever reason. I can’t think of anything else.
 

ZuMBLe

Autocross Champion
Location
NY
Car(s)
Alltrack 6MT
So an upgraded AFE drop in filter and silicone hose to feed the turbo inlet made no difference as well. Snow grate has already been removed as well.

still EPC light for misfire under boost when shifting

Not surprised. Tell them their tune sucks. See if they can work with you to fix it. If not, I really think you should get a refund.
 
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