High Negative LTFT on N/A BRZ causing idling issues

[Chad_W]

How many miles on the original plugs?

[paintdude258]

About 57k on the original plugs. They were definitely fouled. One or two of them had an oily residue on them. I'm assuming it was gas from the leaky injector oring.

[dj2020]

Originally Posted by paintdude258

@tracerit It's funny you bring that up. I had come across the thread you referenced a few times and definitely thought that to be a possibility, but i wanted to rule out all other options before tackling the injector oring possibility.

The short answer to your question, yes, i can replicate that exact problem. Cork popping noise around high throttle, low RPMs. I, like yourself, didn't think much of it at first, but the more and more i read about the bad oring issue and the popping noise that came with it, i suspect a leaky injector is indeed my problem.

Since my last post, I have replaced the Spark Plugs, had a shop check for exhaust leaks, and had a friend look over a few of my data logs.

The spark plugs made a world of difference for the sluggishness i was experiencing.
The shop found no exhaust leaks
My friend didnt see anything irregular with the parameters i recorded.

Is there a diagnostic test or log to run to determine if this is a leak from the direct injectors? I seem to have LTFTs that slowly get more negative with my 2013 JRSC BRZ. I have a hybrid MAF/SD tune. I've cleaned my MAF twice and even routed my CCV to a filtered breather instead of back into my intake to rule out blow by. Like clockwork, it takes about 10 days for my car to build up to -25 to -30% LTFT where it finally throws a code after cleaning the MAF and resetting my ECU. The LTFTs seem to be more negative at idle than when cruising and accelerating. The STFTs swing wildly at times when the throttle is stabbed quickly. I initially thought it was just the ECU compensating for tip in lean condition. I haven't looked for an exhaust leak as I believe that will cause positive leaning fuel trims as the o2 sensors would mistakenly read lean.

[steve99]

Originally Posted by dj2020

Is there a diagnostic test or log to run to determine if this is a leak from the direct injectors? I seem to have LTFTs that slowly get more negative with my 2013 JRSC BRZ. I have a hybrid MAF/SD tune. I've cleaned my MAF twice and even routed my CCV to a filtered breather instead of back into my intake to rule out blow by. Like clockwork, it takes about 10 days for my car to build up to -25 to -30% LTFT where it finally throws a code after cleaning the MAF and resetting my ECU. The LTFTs seem to be more negative at idle than when cruising and accelerating. The STFTs swing wildly at times when the throttle is stabbed quickly. I initially thought it was just the ECU compensating for tip in lean condition. I haven't looked for an exhaust leak as I believe that will cause positive leaning fuel trims as the o2 sensors would mistakenly read lean.

STFT varying widely with throttle application is normal
LTFT is the average of STFT over time in a particular air flow range.

if LTFT is getting over about 10% then you have either a tune problem or a hardware problem like bad sensor or injectors or leaks/

[dj2020]

Originally Posted by steve99

STFT varying widely with throttle application is normal
LTFT is the average of STFT over time in a particular air flow range.

if LTFT is getting over about 10% then you have either a tune problem or a hardware problem like bad sensor or injectors or leaks/

Assuming the MAF is not getting fouled and the MAF sensor is not failing, what is the best way to determine if I have a leaky port or direct injector or a failing o2 sensor? Is there a particular log I can post here for others here to look at? It literally takes a week and a half for the LTFTs to climb to over -25%.

[steve99]

Originally Posted by dj2020

Assuming the MAF is not getting fouled and the MAF sensor is not failing, what is the best way to determine if I have a leaky port or direct injector or a failing o2 sensor? Is there a particular log I can post here for others here to look at? It literally takes a week and a half for the LTFTs to climb to over -25%.

Has this tune and SC install ever worked correctly ?

Have you changed anything, arround the time this problem occurred

Is the diect injection computer under bonnett firmly screwed to mounts as it get its earth via mounting bolts.

Hybrid SD tunes on about racerom 5 i think had some weird issues, you might want to talk to the tuner

Usually if direct injectors are leaking you will get popping out the intake on revving engine.

Its probably going to be difficult to pick in logs as it takes so long to happen.

[dj2020]

Originally Posted by steve99

Has this tune and SC install ever worked correctly ?

Have you changed anything, arround the time this problem occurred

Is the diect injection computer under bonnett firmly screwed to mounts as it get its earth via mounting bolts.

Hybrid SD tunes on about racerom 5 i think had some weird issues, you might want to talk to the tuner

Usually if direct injectors are leaking you will get popping out the intake on revving engine.

Its probably going to be difficult to pick in logs as it takes so long to happen.

Thanks for some of the troubleshooting advice. I started noting slight stumbling about a month ago at idle and under low/moderate load acceleration. That's when I noticed a pending rich code and -25% LTFT. Everything was working fine before then. I automatically assumed MAF was getting fouled. So I cleaned it, made sure MAF Oring was good, and put a breather on the CCV instead of back into the intake (pre Rotrex). This automatically brought my LTFTs back to normal (+/- 7%). I DID NOT reset the ECU or unplug battery. Over the next 10 days, the LTFTs would slowly rise to -25% until a pending rich code would show along with slight stumbling on mild/moderate acceleration. Second round: cleaned the MAF one more time thinking maybe I had some oil residue still getting on the MAF leftover in the intercooler. Same results after about 10 days.

Third round: simply reset the ECU by unplugging the battery for 10 mins. Did not the clean the MAF this time. LTFTs are good right now for the past 3 days. They are sitting at -2.8% at idle and that is where we stand now.

The direct injector ECU is firmly bolted down. No popping noises from the intake or engine when revving. Maybe an occasional mild pop from the exhaust when I let off the gas. Nothing loud by any means.

Come to think of it, there is a pure SD tune I can flash and try to see if this problem persists. I'll wait one more time to see if the negative LTFTs rise again since I'm only on Day 3 post ECU reset. I just wanted to work through any mechanical problems before because the tune was fine for 5 months. Only other change I can think of is a huge consistent change in temp. I'm sitting at 110 Fahrenheit for the past 2-3 weeks. Vegas baby!

[tracerit]

@paintdude258

just wanted to update that I've fixed my issues by going back to the stock airbox (had the perrin regular cai before). although I'm not convinced it's because of my CAI just because I had it tuned with E85 and MAF scaled and it was perfectly fine just about two months ago.

When I took the bumper off, I noticed that the foam filter for the Perrin CAI was smushed down and it was also smushed inwards. The inward position is just the way it's designed, but it being positione down onto the air diverter was concering, so I positioned it up and retorqued the nut hoping my high negative LTFT was due to not getting enough air due to less surface area available to suck air in. I drove without the bumper to test this but still had the hesitation and high negative LTFT.

After this I decided to just put the stock airbox back on. I also cleaned the MAF sensor again, wiped the inside of my Perrin inlet hose (wasn't that dirty, no grime or oil really came off) and then put everything back together.

On first startup I immediately noticed it not taking as long to crank. Just the drive out of my neighborhood was suuuper smooth. fuel trims are normal now, I'm actually running a bit lean, LTFT is at positive 2-5%. Stock tune.

I think maybe the foam filter from Perrin was oiled way too much from the factory (although I didn't have any issues with E85 tune with MAF scaling). I wanted to spray clean it with my Unifilter cleaner set to see if that was the case, but I was just so tired and have to have the stock airbox on to bring it back for my oil leak check anyways. I also tried MAF scaling to fix my high idle a few weeks ago too but that didn't solve anything.

I hope you get your fuel trims sorted out soon!

Edit: so my throttle stabs thst produced a "pop" was actually just my Cai lol.

[paintdude258]

@tracerit

Thank you for the update!

I do find it very ironic that all of my problems seems to have started right around the time I cleaned and oiled my CAI filter.

The reason i originally ruled out the filter being the cause is because i started the car and let it run while the CAI was unplugged completely. While doing this originally, i did not see a change in LTFT. I also think that i should have driven the car first, before ruling out the filter.

@Mishimoto

Is there a specific way to clean the filter that comes with your CAI for the BRZ/FR-S?
I used K&N air filter cleaner and then K&N air filter oil. Have you guys ever run into any issues with clogging up the filter or having air get restricted by the filter?

[Mishimoto]

Originally Posted by paintdude258

@tracerit

Thank you for the update!

I do find it very ironic that all of my problems seems to have started right around the time I cleaned and oiled my CAI filter.

The reason i originally ruled out the filter being the cause is because i started the car and let it run while the CAI was unplugged completely. While doing this originally, i did not see a change in LTFT. I also think that i should have driven the car first, before ruling out the filter.

@Mishimoto

Is there a specific way to clean the filter that comes with your CAI for the BRZ/FR-S?
I used K&N air filter cleaner and then K&N air filter oil. Have you guys ever run into any issues with clogging up the filter or having air get restricted by the filter?

Hey Paintdude!

As far as cleaning and maintenance is concerned, you can follow the same procedure that you would use with any other oiled air filter. If you have any questions about the specific process/cleaning solutions in your kit, your best bet would be to call the kit's manufacturer or look on their website for specific instructions.

Additionally, here is a general guide on the process.

We have not had any issues to speak of with filters becoming clogged, but if you continue to have problems, you can contact our customer service department for support and any further questions.

Thanks a lot,
-Gardiner

[paintdude258]

@tracerit UPDATE Holy Moly..... UPDATE! My problem is fixed!

So per your story about the airbox, I decided that I had two options.

Go through the pain staking task of taking off the bumper to change my intake, or attempt my go at Calibrating my MAF.

The MAF idea required A/C, so that's what I did.

I used VGA's tool, took all the necessary logs, put my numbers into the tool, uploaded the new numbers onto my tune...

Car runs like a DREAM! LTFT stays within -+1 at all times!

I am going to rescale it once more, then do closed loop, but after 100 miles with the new calibration, fuel trims are holding strong.

It would appear as though I didn't clean off the intake enough when I oiled it, causing the amount of air passed through the filter to decrease.

[Mishimoto]

@paintdude258 Glad you were able to solve this issue! I was just down in Austin for a visit the other week and there were quite a few roads that made me really wish I had my car down there, so enjoy that BRZ!

-Gardiner

[gonzo]

Originally Posted by cjd

http://www.instructables.com/id/Find...ng-your-hands/

Take your time exploring and I recommend an ear plug in the ear you're not using. The noise at a leak gets quieter the smaller the leak, and if you get impatient and move too fast or have the tube to far away you may miss it.

I used this method to find the leak in my exhaust.

[DGSeries10]

@tracerit I'm very curious as to how this resolved. Was it indeed a leaky injector? I'm having the exact same issue. High negative LTFT off throttle and idle (-16%) but rock solid 0% on throttle. I'm running the AEM intake with AEM's maf tuning solution and stage 1 OFT.

Originally Posted by tracerit

Are you referring to the O ring around the MAF sensor unit that plugs into the intake?

I'm having the same issue, -10 to -15% LTFT off throttle and idle but 0% on throttle. I've rescaled the MAF and have tried stock and the Stage 1 OFT tune but the same issue occurs.

I looked at my O ring (referring to the MAF sensor unit) and it was slightly out a bit on my Perrin CAI, so I reseated it with some lube to get it fitting in but I'm having the same high negative LTFT. A piece of the O ring is slightly torn but still intact, so I'm going to try to find a replacement tomorrow at Home Depot. Doubt it will fix it though since it's super snug unless the smallest amount of break can cause the high negative fuel trim.