High Negative LTFT on N/A BRZ causing idling issues

[steve99]

Originally Posted by Wepeel

Shiv told me that on the OFT the O2S2 and Wideband AFR readings are not accurate - fwiw. O2S2 will always read 0.0v.

yes for sure it wont be accurate its calibrated for a aem wideband or something, but my oft will read wideband afr log address and you can see it move arrount and not just stuck on 17, im just using it as an indication the sensor is connected and producing some sort of signal. Its also possible it reading 17 all the time as that log chanbel is not set up on his particular rom calid.

heres a log with afr and wideband afr channels logged

http://datazap.me/u/steve99/uel-head...=0&data=1-6-13

[paintdude258]

@steve99 Very interesting looking at your chart. I called one of my friends running the same map as myself, and he confirmed his tablet read the same. 0.0v for O2S2 and 17 for wideband AFR. I figured this for sure pointed to the rear O2 sensor, but now I'm having second thoughts before installing it. If my back sensor is good, id prefer to just return the one i purchased.

*Update*

I had a friend come over yesterday to swap out MAF sensors... He left his hood lock keys at home, so that was a fail.

In the mean time, i took it upon myself to do 3 logs, 2 of which were extended highway cruising, and 1 was city driving. I used the VGI MAF scaling tool with what i found.

I have only driven the car a few miles after reflashing with the updated MAF Scaling, so we shall see. It was neat running that application and seeing my numbers change, and getting to see the graphs comparing smoothed vs actual curves.

This being said, i have only adjusted closed Loop, not open. I am going to let my trims settle, log Closed Loop 1 more time, and then mess with open loop.

Hopefully i can get a friend over today to test out the Bad MAF idea.

THIS FORUM ROCKSS!! Thank you guys for all of the help!

[paintdude258]

My Command AFR Vs AFR look to be fairly stable. Command usually sits around 14.9 and actual AFR sits around 14.5. They progress through the RPM band to match the numbers you laid out Steve. I will try and post my logs tonight to see if anything looks out of wack.

Originally Posted by steve99

While the front 02 sensor is the primary fueling sensor, the rear sensor also effects cruise fueling and weird stuff will happen if you disconnect or the rear 02 sensor is faulty, unless you disable the AF#3 corrections in the tune and disable some cel codes.

@paintdude258 log your Commanded AFR vs AFR as well as fuel trims. If the AFR looks ok ie around 14 cruise 13 mild acceleration and 11-12 wot and following commanded AFR reasonably well then the front o2 is likely ok, but for some reason the ecu is applying big correction to make that happen. That could be intake or exhaust leak, dirty MAF sensor etc.

[steve99]

Originally Posted by paintdude258

@steve99 Very interesting looking at your chart. I called one of my friends running the same map as myself, and he confirmed his tablet read the same. 0.0v for O2S2 and 17 for wideband AFR. I figured this for sure pointed to the rear O2 sensor, but now I'm having second thoughts before installing it. If my back sensor is good, id prefer to just return the one i purchased.

*Update*

I had a friend come over yesterday to swap out MAF sensors... He left his hood lock keys at home, so that was a fail.

In the mean time, i took it upon myself to do 3 logs, 2 of which were extended highway cruising, and 1 was city driving. I used the VGI MAF scaling tool with what i found.

I have only driven the car a few miles after reflashing with the updated MAF Scaling, so we shall see. It was neat running that application and seeing my numbers change, and getting to see the graphs comparing smoothed vs actual curves.

This being said, i have only adjusted closed Loop, not open. I am going to let my trims settle, log Closed Loop 1 more time, and then mess with open loop.

Hopefully i can get a friend over today to test out the Bad MAF idea.

THIS FORUM ROCKSS!! Thank you guys for all of the help!

ok if you mates rear 02 reads 0V and 17 afr all the time I would say the logging for wideband AFR is not working on for your rom calid (the logging addresses are independently set for each rom calid) so just ignore it its likely ok.


If commanded afr and afr are in sync its a good sign that things are ok with front 02 sensor as well, it might be just maf scaling off due intake.


if you have access to Toyota techstream you can monitor rear 02, im not sure if android torque app will monitor rear 02 sensor but worth a check

[Wepeel]

Originally Posted by steve99

if you have access to Toyota techstream you can monitor rear 02, im not sure if android torque app will monitor rear 02 sensor but worth a check

Torque does report what seems like reasonable voltages for rear O2 sensor, between 0 and 1 volt.

[paintdude258]

* UPDATE *

I decided i would dive into the MAF scaling possibility. I did several highway logs, city logs, and slow speed driving logs. Then i did a second set of the same logs and tweeked a bit more. It didnt feel perfect, but defintely helped.

Then last night, i had a friend come over to switch me his MAF sensor to rule out a bad MAF. Turns out, after seeing his, turns out I didnt seat my o2 sensor oring all of the way into my intake. It was causing a vacum leak, and changed the position of the sensor itself.

Got the oring seated, and even though my trims haven't settled yet from going back to my original tune, my car feels AWESOME!!!!!

Problem solved so far! Thanks to everyone who helped. I sure learned a lot along the way.

[andrillox]

I'm glad you were able to fix it.

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[tracerit]

Originally Posted by paintdude258

Then last night, i had a friend come over to switch me his MAF sensor to rule out a bad MAF. Turns out, after seeing his, turns out I didnt seat my o2 sensor oring all of the way into my intake. It was causing a vacum leak, and changed the position of the sensor itself.

Got the oring seated, and even though my trims haven't settled yet from going back to my original tune, my car feels AWESOME!!!!!

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.

[paintdude258]

@tracerit my fuel trim problems came right back. My car ran amazing for the first 10 miles after I flashed it back to a fresh tune, but as soon as the trims started to learn and settle, they went right back to -10% to -15% at all times.

I had a friend who had a busted oring at the MAF. Unfortunately for us, this caused him to read an extremely high lean fuel trim, not a rich one like we are experiencing. Plausable, but dosent sound like the right fix.

At this point, I am perplexed at my next step.

Get a smoke test done to see if any small leaks exist, causing air to escape before it reaches my primary o2 sensor.

Pull out the direct injectors to see if any of the seals are bad, letting excess fuel into the cumbustion chamber.

Pay a tuner to look at it, and see if he can diagnose.

This is driving me nuts, and I don't know where to go next without spending a whole bunch of money.

Any thoughts on the fact that my car ran amazing right after the tune, then adjusted for a rich trim? @steve99

I also have 3 third gear WOT pulls if that information might help you see something I'm missing.

[tracerit]

because we're running rich and the ECU is leaning it out, the issue is more like likely intake /fuel related rather than exhaust?

I'm asking because the V-Clamp locking the midpipe to the muffler of my Perrin exhaust has always been loose for the last 3 years, it's like 89% tight. But I've never had an issue with fuel trims for that time.

[paintdude258]

@tracerit I agree with you about the exhaust not being the culprit.

The last time i was under my car, 2 weeks ago, i noticed that i had a small exhaust leak coming from the "header to block" connection. I tightened the bolts and went on way merry way.

This area could certainly be a problem if its leaking air. It would cause the primary o2 to read rich because its not seeing as much air as the MAF sensor is letting through.

I will have to check on that and get back with you.

[cjd]

An exhaust leak reads lean, not rich...too much oxygen means not enough fuel to use it up. It ends up running rich as a result, assuming trims 'correct' to the target properly.

C

[tracerit]

Originally Posted by andrillox

Leaky fuel injector, excessive fuel pressure due to bad fuel pressure regulator or restricted fuel line, extremely dirty air filter or restrictions in air intake system, exhaust restrictions (clogged converter, crushed exhaust pipe or plugged muffler) or you may have a bad o2 sensor (output shorted to voltage which gives you a rich reading).

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So I'm thinking my car has a leaky fuel injector. Looked around the forums and found this thread: http://www.ft86club.com/forums/showt...=injector+leak

It mentions a pop at high throttle, low RPM. I've noticed this when I shift from 2nd to 3rd gear at about 2500rpm and give it high throttle leaving my neighborhood. I always thought it was just my exhaust. Going to clean up the car and then bring it in for warranty, have them look at my engine seepage too lol. I swear my 2013 has all the common first year issues it seems...
@paintdude258 are you able to replicate this pop noise at low RPM, high throttle coming from a cold start?

[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.