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Old 03-27-2019, 04:28 PM   #1
Minidude147
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short term fuel trims high at idle and and partial throttle

Hi all I recently installed a Jackson racing supercharger kit on my car and a delicious flash and go tune. I have borla uel headers, and am experiencing high stft at idle and partial throttle especially on start up. they start to trend lower to around 8-12 after driving for awhile but are still positive. I have checked the pcv valve, the map sensor orientation and don't believe I have an exhaust leak as I used 2 grimspeed gaskets where the header meets the engine. I am stumped and I cannot get my tune dialed in until I figure this out thanks. its worth noting that the idle and driving feels fine maybe a little on the high side for idle around 900. otherwise the car drives great, id appreciate any ideas or feedback on what went wrong.
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Old 03-27-2019, 04:38 PM   #2
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A small intake leak will be about 15% STFT, a large one will max it at 29.7 and the car will run like shit.

I've never done a Jackson install but if you went into boost I would make sure the cap and the hose under the throttle body are still attached. Other places beside PCV would be the block nipple under the AC compressor.
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Old 03-27-2019, 04:41 PM   #3
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thank you for the suggestion I will check those out, is it possible that if the tne he sent me doesn't account for my catless headers it could cause me to run lean at idle?
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Old 03-28-2019, 01:11 AM   #4
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Also check idle vaccuum.


Engine off manifold pressure should ve 1 bar ie atmospheric


Engine idle should be about 0.3 to 0.4 bar if its closer to 1 bar you likely have intake leak or bov leak
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Old 03-28-2019, 01:55 AM   #5
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Idle vacuum should be like -10 psi right? If it's sometimes weaker, like at -7 psi, is that normal?
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Old 03-28-2019, 05:53 AM   #6
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Quote:
Originally Posted by Mr_Eyo View Post
Idle vacuum should be like -10 psi right? If it's sometimes weaker, like at -7 psi, is that normal?



Yeah -7 seems a bit low
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