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2018 PCP Scat Pack w/dynamics
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Discussion Starter · #1 ·
Hey guys, so I installed kooks LT headers w/ catless mids recently and got it tuned. Ever since it got tuned, I’ve noticed cold and warm starts are a bit rough. Cold starts will have large rpm dips (+-500), so it’ll sound like it’s about to die, then rev up. Sometimes on warm starts, the rpms will start very low, almost like it’s just weak. Before the tune, it just always fired right up. Like it roars to life, and slowly idles down. Does anyone know what might be going on? All temps are fine, no lights are on, and the car drives just fine. But these startups worry me a bit. Does anyone know what might be going on? My tuner suggested it’s probably a mechanical issue.
 

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I don’t know a thing about tuning but I had this exact same thing going on with my untuned Scat Pack for about a year. A performance shop near me suggested it might be the EVAP purge valve and that’s exactly what it was. It’s about $15. It’s on the back left side of the engine and kind of pain in the ass to get your hand on. But otherwise a simple and cheap possible fix.
 

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What tuner are you using...diablo or HP tuners? If HP tuners post up your tune on the HP tuners site...lot's of knowledgeable tuners their that can look at the tune and suggest changes. If diablo...I am afraid you are at the mercy of pro-tuners that have the CMR software to make changes.
 

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2018 PCP Scat Pack w/dynamics
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Discussion Starter · #4 ·
I don’t know a thing about tuning but I had this exact same thing going on with my untuned Scat Pack for about a year. A performance shop near me suggested it might be the EVAP purge valve and that’s exactly what it was. It’s about $15. It’s on the back left side of the engine and kind of pain in the ass to get your hand on. But otherwise a simple and cheap possible fix.
interesting! I will look into this, thank you!


What tuner are you using...diablo or HP tuners? If HP tuners post up your tune on the HP tuners site...lot's of knowledgeable tuners their that can look at the tune and suggest changes. If diablo...I am afraid you are at the mercy of pro-tuners that have the CMR software to make changes.
I’m not sure tbh, I can ask my guy tomorrow.
 

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interesting! I will look into this, thank you!




I’m not sure tbh, I can ask my guy tomorrow.
I had the same problem after I did my cam, but it would never show up until a few days of driving on the tune. Tuner revised it and no more problems starting. If it's not the tune(probably is) I'd check the intake manifold bolts as they ALWAYS come loose. My brother just bought a '10 R/T and 3 of the manifold bolts were basically completely unthreaded
 
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The Bacon Hauler (‘12 Cop Charger)
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Check the car’s VIN for any outstanding emissions recalls, more specifically one which deals with a faulty EVAP canister.

I don’t know if that recall’s list of symptoms includes these issues you describe, but I know there is an EVAP recall out there for some LX cars, and the earlier post mentioning the EVAP system made me think of it just now, so thought I would mention it just in case.
 
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2016 SXT Plus Blacktop
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The UB4 evap recall was 2013-2016

A Guy
 
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Try resetting your adaptives. Normally whenever I make changes to my tune, right after I flash the PCM I clear all adaptives an do a throttle relearn (not sure if diablo has that capability though). On a side note, check your intake bolts to make sure they have not loosened.
 

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Discussion Starter · #9 ·
What tuner are you using...diablo or HP tuners? If HP tuners post up your tune on the HP tuners site...lot's of knowledgeable tuners their that can look at the tune and suggest changes. If diablo...I am afraid you are at the mercy of pro-tuners that have the CMR software to make changes.
My tuner informed me, they are using hp tuners.
 

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Discussion Starter · #10 ·
I had the same problem after I did my cam, but it would never show up until a few days of driving on the tune. Tuner revised it and no more problems starting. If it's not the tune(probably is) I'd check the intake manifold bolts as they ALWAYS come loose. My brother just bought a '10 R/T and 3 of the manifold bolts were basically completely unthreaded
Sent a video to my tuner of the problem, he said it’s most likely a vacuum related issue. I’ll get those manifold bolts checked out, and post a video soon. Thanks!
 

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Yeah the manifold bolts tend to back out over time even on a low mileage challenger that has not had the manifold touched. At ~15 kmiles when I checked mine it took almost 2.5 turns to get the correct torque...several months later they backed out again. If you have any fuel staining around the manifold then most likely they are loose. Best way to fix is to pull the manifold off, install new seals and add blue loctite to the threads (bolts are a "captured" design so if you try removing and installing them alone then the loctite will just wipe off).

Although if you noticed a change after a tune it most likely is the tune itself. Installing headers does not require intake manifold removal but they do change the way the O2 sensors read as they sit further from the exhaust ports. That's why the O2 transport delay is usually increased by 50% in the tune.
 
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