High Negative LTFT on N/A BRZ causing idling issues

[paintdude258]

Hey guys,

I have searched and searched, and actually found some good info about my problem, but nothing i find seems to help me.

I have a Mishimoto CAI, Tomei UEL Headers, and Magnaflow cat back.

At idle, i noticed my LTFT sit anywhere between -11% and -20%. These numbers have slowly increased over the last few weeks. When i hit the gas, these trims reduce back to around -7% to -5%.

I have refitted my exhaust and checked for leaks, cleaned and inspected my MAF sensor, and i have disconnected the battery and pumped the breaks without any luck.

I recently cleaned by CAI filter with an oil based solution, washed it out, and let it dry over night.

A while back i had code P0351 which is coil pack 1 i believe. I switched coil pack 1 and 3 and the problem went away.

Can anyone advise on what my next steps should entail to have my trims settle down, and help my car idle smoother?

Thanks in advance,
Blake

[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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[paintdude258]

Thank you Andrillox for all of the sugguestions!

So to start tackling this issue, where would you start with your recommendations above? Should I run a fuel system cleaner, inspect my injectors?

When checking for a bad O2 sensor, should I just take it out and clean it, or should I check my O2 sensor readings and be looking for anything specific?

[andrillox]

Well that depends on a few things. Is the check engine light on?

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[paintdude258]

No Check engine light. I have the openflash tablet mounted on my dash, and my car started running rougher than usual, so i was able to pin point something being "Off" rather quickly.

[andrillox]

At this point I would start with just visually inspecting both o2 sensors and if too dirty, you can spray a little brake cleaner to make it really clean. I believe the open flash has the ability to bypass a check engine light for people with headers or different mods that may trigger one. I would also check to see if the maf is dirty and perhaps reading less air than what is actually going into the motor. Have you tried running without the air filter you recently cleaned to see if it runs better? Another thing that may be happening is that possibly the exhaust may have a leak somewhere before one of the two o2 where air is actually going in. If this is happening then the o2 is measuring air that has never actually made it into the motor, yet it is passing through the exhaust due to the exhaust/header leak. If this leak is the problem is more likely to be more noticeable during idle and dissipate as you accelerate.

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[paintdude258]

You are correct, the Openflash does bypass the 2nd o2 sensor all together! I have had that in place since day 1! I have not tried taking off the intake filter itself. That will definitely be up next. I have thoroughly cleaned the MAF sensor with electrical contact cleaner. Should I use the same electrical cleaner on the o2 sensor, or just break cleaner? I have both solutions.

I took off the entire over pipe and back system off this weekend and cleaned all connections, tightened everything up, with no results. That being said, I did not pull either exhaust piece that is pre o2 sensor. Header and front pipe will be next on the list, just more of a PITA!

The negative Trims are much more prominate at idle, hovering around -11%! I even tried putting on an older off the shelf nap I have just for the heck of it... No change! The trims reverted right back to negative.

I will inspect the header o2 sensor, clean it, and then take off the intake filter! Will keep you posted with my results!

[cjd]

An exhaust leak after the header can also cause air intake between pulses at idle and around town, though header to overpipe is the more likely culprit... and probably not a chance art the muffler side. You can also explore for leaks with a vacuum at the tailpipe and a tube to the ear.

[paintdude258]

Thanks for the ideas cjd, I will be sure to take a more thorough look at the rest of the exhaust I didn't get to the first go around.

What is this method cjd you speak of that involves a vacuum and a piece of hose?

[cjd]

Originally Posted by paintdude258

Thanks for the ideas cjd, I will be sure to take a more thorough look at the rest of the exhaust I didn't get to the first go around.

What is this method cjd you speak of that involves a vacuum and a piece of hose?

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.

[paintdude258]

Could the Openflash tune I have on the car cause this issue? A friend of mine swears that the tune could be the issue of my fuel trims running rich. I have not scaled my MAF after adding the mishimoto CAI, but Mishimoto claims the intake dosent need to be scaled.

Any ideas @shiv

[steve99]

Originally Posted by paintdude258

Could the Openflash tune I have on the car cause this issue? A friend of mine swears that the tune could be the issue of my fuel trims running rich. I have not scaled my MAF after adding the mishimoto CAI, but Mishimoto claims the intake dosent need to be scaled.

Any ideas @shiv

quite likely you will need to do maf scaling if you have changed the entire intake

[paintdude258]

Just a little update. I have checked all exhaust fittings from The header back and found no leaks. I have cleaned my MAF and both of my O2 sensors. I have tried three different OTS maps. My LTFT are still continuing to climb. They are now sitting around -15% to -18% at idle and around -8 to -10% while driving.

[steve99]

Originally Posted by paintdude258

Just a little update. I have checked all exhaust fittings from The header back and found no leaks. I have cleaned my MAF and both of my O2 sensors. I have tried three different OTS maps. My LTFT are still continuing to climb. They are now sitting around -15% to -18% at idle and around -8 to -10% while driving.

If you have never adjusted the maf scaling when you instaled the mishimoto intake thats likely your problem.
You will also see ltft vary at idle say 7% or so due to large temp changes in intake air this is normal.

see links below on maf scaling

http://www.ft86club.com/forums/showthread.php?t=64790