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09-02-2021, 10:47 AM | #1 |
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Troubling STFT after ACE Header install
Hello everyone,
I'm posting because I'm currently having some trouble with my fuel trims after a recent ACE A350 header install and STG 2 tune by Delicious Tuning. Any help/recommendations or lessons learned would be greatly appreciated. I recently installed my ACE A350 header/op as well as a drop in K&N air filter. After a few tune revisions from Delicious Tuning, the car feels amazing and seems like it's driving fine, but my data logs say otherwise. Cruising and Idle seem fine, but when I apply throttle, the STFT likes to jump to ~-20-30%. This specifically only happens under throttle, and then the STFTs return to normal. The LTFTs look great, and I think my AFR looks good but I'm new to tuning and reviewing data logs, so maybe I'm mistaken. Has anyone had a similar experience? All bolts on the header seem to be torqued down properly and to the correct torque, MAF looks clean and I don't see any visible exhaust or intake leaks, but it's possible that there's a leak small enough for me to not notice without a smoke test. I've also checked the bolts and ground on the fuel control module and it checks out. https://datazap.me/u/jf86/ace-a350-s...0&data=3-21-22 Thank you! |
09-02-2021, 11:22 AM | #2 |
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Please tell me you have talked with Delicious about this before coming here and asking.
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The Following 2 Users Say Thank You to x808drifter For This Useful Post: | CSG Mike (09-13-2021), Lantanafrs2 (09-02-2021) |
09-02-2021, 11:41 AM | #3 |
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I have, thanks. They recommended checking my fuel control module for proper ground and ensuring that there aren’t any missing bolts. I checked and everything there looks fine.
I also flashed the ECU back to stock and the same problem exists, leading me to believe it’s a mechanical issue and not related to the tune. I should also note that I’m getting a lean code P0171 due to the instantaneous jumps in STFT. |
The Following User Says Thank You to Jpf86 For This Useful Post: | x808drifter (09-02-2021) |
09-02-2021, 12:31 PM | #4 | |
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09-02-2021, 01:04 PM | #5 |
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The car is only 6 months old so I suspect if there’s a mechanical problem, it occurred during the install. The header/op and drop in air filter are the only mods. I suspected it was an exhaust leak but double checked the torque on the bolts after a few days of driving/logging and they looked good. I was accidentally a little rough on the O2 sensor cables when removing the stock header (the cable was snagged in the engine bay and I didn’t realize) but there’s no visible damage so I don’t want to replace the sensors if my problem isn’t characteristic of a bad sensor/cable.
I haven’t seen any posts from anyone else that shows healthy fuel trims except for STFT under throttle so I’m at a loss. My best guess is that it’s a small leak somewhere that is so small it only leaks under throttle, but I’m hoping someone else has experienced something similar before I start blindly replacing parts. My next step will probably be having a mechanic leak test the intake/exhaust, then replacing O2 sensors if I don’t receive recommendations to try something else first. Thanks! |
09-03-2021, 01:02 AM | #6 |
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Pretty normal for stft to move round a lot on large sharp throttle movenents that normal
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The Following User Says Thank You to steve99 For This Useful Post: | Dzmitry (09-03-2021) |
09-03-2021, 10:10 AM | #7 |
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Well there you go, looks like @steve99 has a point. I mean everything else in your log looks perfect, so it makes sense that nothing should be wrong. Are you engaging the throttle fairly quickly as Steve describes?
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09-04-2021, 09:54 AM | #8 |
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Thanks for your reply! I agree that it’s normal for STFT to move around quite a bit under throttle, but it deviates so much that it triggers P0171 and puts traction control on until I clear the code. I’d say that’s definitely not normal, but if it’s not unhealthy then maybe I’ll just have to live with clearing codes every time I drive. It does only happen when I very quickly engage the throttle.
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09-08-2021, 01:09 PM | #9 | |
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09-09-2021, 03:19 PM | #10 |
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Make sure all the studs are in place still at the header to OP flange. I did the same- checked torque after a few days, all good. Some unknown time later I lost at least one. Might have been two, or maybe the second was later... Don't even recall.
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Second chance build... or whatever it is.
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