Fuel Trims Advice rough idle

[judah304]

2019 Si 8500 miles. Put a 27Won CAI on 3 weeks ago. Car runs great.
Take car to get inspection (NYS). Next day car idles rough. Sounds weird on startup like doesn't want to start for split second. Seems to be missfiring/stumbling at idle. No miss fire codes. Hooked up OBD2 sitting idling in driveway STFT is -16.4 and LTFT is -21.9. See picture

Any ideas before I put stock intake back on to see the change?

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[hobby-man]

I would start with checking all your intake couplers and make sure nothing came lose. Seems like a major air leak somewhere.

 

[saiko21]

yeah, looks like there's a leak somewhere

 

[alxgravel]

Hi, I'm having the same problem here in mtl since I installed my 27won, on idle I'm running rich like you. Its weird because its only on idle. I did change my plug and cleaned my maf sensor and I did the injector clean up at the dealer...this helped a bit but still running rich on idle!

Next think to look its maybe clean the oxygen sensor.

I know when I start the ac on the STFT will drop like -25 to -10 to -15 so This his the same data with the stock intake

27won rmm , intake and tsp stage 1 map 3
Running on 94 oct with 10% ethanol ( petro canada 94 oct)

 

[Gradyjim024]

I would start with checking all your intake couplers and make sure nothing came lose. Seems like a major air leak somewhere.

I'm having the same problem after I put on a prl cobra race maf. I checked all the couplers and they were all tight. I'm on phearable with race calibration. Even tried running basemap with race calibration and nothing changed. I changed the maf sensor today and still running rich. Vega from phearable told me I either had a post maf leak or incorrect housing. And I've changed my plugs.

 

[hobby-man]

I'm having the same problem after I put on a prl cobra race maf. I checked all the couplers and they were all tight. I'm on phearable with race calibration. Even tried running basemap with race calibration and nothing changed. I changed the maf sensor today and still running rich. Vega from phearable told me I either had a post maf leak or incorrect housing. And I've changed my plugs.

If you're running super rich, the MAF housing is correct, and there are no air leaks, next thing I'd be looking at is leaking fuel injectors.

 

[Gradyjim024]

If you're running super rich, the MAF housing is correct, and there are no air leaks, next thing I'd be looking at is leaking fuel injectors.

Okay. I found a site for them as a set but it doesn't state if it comes with everything I need for the replacement as far as the orings and seals go.

 

[kshawn]

Easiest way to determine if the problem is with the intake or something else on the car would be to reinstall the stock one and see if the trims are back to normal.

 

[brendonsiX]

I'm having the same problem after I put on a prl cobra race maf. I checked all the couplers and they were all tight. I'm on phearable with race calibration. Even tried running basemap with race calibration and nothing changed. I changed the maf sensor today and still running rich. Vega from phearable told me I either had a post maf leak or incorrect housing. And I've changed my plugs.

Hey! Can I ask you what your numbers look like at idle? I have the same mods (race maf) and phearable tune with LTFT hitting -10 after maybe 5-10 minuted of idling but drops down quick when driving. Only thing I have is a injen hydro shield which I'm thinking might restrict my air flow a little.

 

[Gradyjim024]

Easiest way to determine if the problem is with the intake or something else on the car would be to reinstall the stock one and see if the trims are back to normal.

Fuel trims are still running high on stock intake and factory tune

 

[Gradyjim024]

Hey! Can I ask you what your numbers look like at idle? I have the same mods (race maf) and phearable tune with LTFT hitting -10 after maybe 5-10 minuted of idling but drops down quick when driving. Only thing I have is a injen hydro shield which I'm thinking might restrict my air flow a little.

At idle my stft fluctuates from like -10 to as high as -25. When I'm cruising with barely any throttle it is showing -15 and sometimes higher.

 

[brendonsiX]

At idle my stft fluctuates from like -10 to as high as -25. When I'm cruising with barely any throttle it is showing -15 and sometimes higher.

Stft will always fluctuate alot as it shows what's currently going on and LTFT is long term values, what does your LTFT look like at idle compared to normal driving?

 

[Gradyjim024]

Stft will always fluctuate alot as it shows what's currently going on and LTFT is long term values, what does your LTFT look like at idle compared to normal driving?

At idle my ltft will reach in the -20s and at normal driving it averages about -10 -14

 

[Gradyjim024]

Stft will always fluctuate alot as it shows what's currently going on and LTFT is long term values, what does your LTFT look like at idle compared to normal driving?

I dont think stft should go into the 20s or up in either variable unless you got a fuel issue.

 

[kshawn]

At idle my ltft will reach in the -20s and at normal driving it averages about -10 -14

Sounding more like injectors

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