Troubleshooting a Leak with OFT

[Lakitu]

@FRSBRZGT86FAN @steve99

Hello guys, I've posted the datalogs.

Idle:
https://datazap.me/u/lakitu/idle-dri...og=0&data=1-11


Casual:
https://datazap.me/u/lakitu/idle-dri...og=1&data=1-11


Aggressive:
https://datazap.me/u/lakitu/idle-dri...og=2&data=1-11

I did just flash with the new tunes, I wonder if the ECU might still be learning?

It's the same symptoms all over again that I've seen a few times before whenever I mess with the ECU. The car feels sluggish and just literally struggling to move. Gas pedal seems to be "missing" about 2 inches of actuation on the press. I've seen this kind of poor performance before though. It ends up going away after A LOT of driving, but I am worried that there could be leaks. I did go ahead and tightened/torque down the exhaust nuts and bolts, found there were two between front pipe and midpipe that I missed! (oops!!). Everything else clicked immediately at the torque wrench.

The MAF re-scaling thing is something interesting that I have considered and tried to look into but gave up on. Had felt I didn't really need to worry about that anyway, since Grimspeed claimed that their CAI is very similar to stock and that is why I went with them over other options. I do wonder if I can get a little bit more response time and performance out of it if I am able to scale the MAF properly.

I'll check the intake and MAF sensor today, that's a good point about the gasket. I'll admit that I haven't checked, hell there could be leaves on the bottom of the filter clogging it up or something.

[Lakitu]

Also have some old logs from when I was fiddling around with the data logger. I'm not sure if this was Stage 1 OFT before the header and Stage 2+, but its definitely before the CAI.

https://datazap.me/u/lakitu/older-logs?log=0&data=10

[Lakitu]

What the hell is up with all these extra line breaks in everything I submit?

[Lakitu]

Current setup pattern looks to be a solid -2.34 ltft, 0 stft while moving.

In old setup, I don't even know what the fuck is going on with those numbers lol. stft drops hard into negatives (sometimes), ltft stays 0. Exact opposite!!?

[FRSBRZGT86FAN]

Originally Posted by Lakitu

Current setup pattern looks to be a solid -2.34 ltft, 0 stft while moving.

In old setup, I don't even know what the fuck is going on with those numbers lol. stft drops hard into negatives (sometimes), ltft stays 0. Exact opposite!!?

Anything happen after checking the maf and intake and such? How about torquing the exhaust system down?

I noticed on the aggressive log you got -16 LTFT at some points still...

[Lakitu]

Torqued the exhaust bits down yesterday and drove around for those logs.


Today, checked the intake, tightened all the hose clamps from filter to throttle body, checked the MAF sensor, it looks slightly dusty but still orange with the o-ring in tact. Reinstalled it and tightened the two screws as best I could. Checked the filter, looks ok. Changed the oil in the car since it was time, then tried my best to tighten down the O2 sensors. Saw some of the threads on one of them just barely visible, as if it didn't seat in properly. This could be the issue, but this means I'm gonna have to pull the header out. (screams) I don't have a wrench big enough so had to use a crescent wrench, but adds risk of stripping them. Wonder if I can just put some RTV around the fittings and see if that helps?



After all that, the LTFT is getting higher now!! Got a new log now with some more casual driving, and then a 3rd pull. Car feels a lot more responsive, slightly lower in volume, and now LTFT is hanging around -11 to -14.



I can't think of anything else to torque down!



https://datazap.me/u/lakitu/drive-ca...l?log=0&data=1

[Lakitu]

I wonder if I should have put RTV where the overpipe and frontpipe connect. There is no gasket there at all, just the (vband?) clamps. Can that really work? JDL designed it that way specifically. The same is true where the midpipe connects to the muffler.

[steve99]

Originally Posted by Lakitu

I wonder if I should have put RTV where the overpipe and frontpipe connect. There is no gasket there at all, just the (vband?) clamps. Can that really work? JDL designed it that way specifically. The same is true where the midpipe connects to the muffler.

Be unusual to get negitive fuel trims with an exhaust leak usually sends trims positive.

Check both you o2 sensors are not loose and screwed in all the way so metal ring is not loose, re tap header threads if you need to dont use excessive force on o2 sensors it breaks them. Also dont use any o2 spacers

[Lakitu]

So with a severe negative LTFT is it a good clue that the leak is before or at the sensors, and not after them (severe positive LTFT)?



I'll re-tap the sensors and hopefully that fixes it. If its not that, I'm not sure what else it could be. I guess I can also try re-seating the headers, and add RTV to the grimmspeed gaskets I have on them.

[Jasonb]

With negative fuel trims I don't think you have a leak. I've been battling negative fuel trims and my intake is all stock. I rescaled my MAF and I think I'm good now.

If air was leaking near the O2 sensors it would make them read as lean and try to add more fuel causing positive LTFT.

[Kodename47]

Large negative trims could be due to bad O2 sensor, injectors gone faulty etc or intake leak. Exhaust leaks tend to be positive trims.

[Lakitu]

I am, definitely going to look into scaling the MAF. Thanks guys

[Jasonb]

Originally Posted by Lakitu

I am, definitely going to look into scaling the MAF. Thanks guys

I would do that. My car is a 2017 with 12,000 miles, with stock intake and stock filter and I was getting fuel trims as bad as -14.8. scaled my MAF and am seeing between -3.12, and +2.34. so even stock MAF scaling can be off a bit.

[Lakitu]

MAD GAINZ


MAF Scale Before
Attachment 167555

MAF Scale After
Attachment 167556


My car is so fast now.