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Rough/Weak startups after tune

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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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2015 RT 5.7 M6
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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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2015 RT 5.7 M6
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12,769 Posts
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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