Toyota GR86, 86, FR-S and Subaru BRZ Forum & Owners Community - FT86CLUB - Negative Short term fuel trims at idle w/ no obvi leak

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Negative Short term fuel trims at idle w/ no obvi leak

Has anyone encountered a turbo application that resulted in negative short term fuel trims at idle that range from 0% to -20% with no obvious vacuum leak?
FMIC setup with EBC and BOV
PCV Valve has been switched to an STI PCV Valve
added 9 Clamps to pcv system
EcuTek tuning
Throwing code P0068.
MAP sensor replaced with new Omni 3 Bar.

consensus is vacuum leak, but haven't been able to find a leak.
What could cause this?
Defective equipment?
Bad install?
Bad tune file?
Please don't say it has to be a vacuum leak?
:search::sigh: HALP
log attached
Really stuck on this one.

Clean your MAF sensor.

Perhaps adding catch cans to your car will help, as could adding a check valve to your manifold to crank case line.

Quote:

Originally Posted by CSG Mike (Post 2244655)

Clean your MAF sensor.

Perhaps adding catch cans to your car will help, as could adding a check valve to your manifold to crank case line.

I'll definitely take care of those.
The shop just said, "Your car isn't running timing"
any ideas on that?
The STI PCV Valve should be enough to prevent any vacuum issues that the check valve would address, but for a couple dollars I'll gladly install one.

Is this a mechanical or tuning issue?

Could this have happened after hard pulls for logging?

Quote:

Originally Posted by IBill4You (Post 2244760)

If it's a result of the hard pulls, then either something on your car changed (e.g. boost leak, dirty sensor, etc.), or the tune is bad and the ecu is compensating.

Your advanced multiplier is 0.16 which is very very bad.the ignition will run on a retarded map . it knocks everywhere at medium load. It think the tune is bad . and the MAF scaling is way off . you're not geting enough fuel at medium load, hence the knocks .

Vacuum leak was ruled out by a shop. They uninstalled and reinstalled the kit to check for DIY errors, of which thankfully there were few and none that would cause this.
I'm waiting on a new tune file to verify bad tune.

I have a gut feeling it is the tune, but I know part of that is a fear of what else it could be.
If it does turn out to be the tune, I'm going to have spent more than I paid for the tune to have it diagnosed and corrected. Not happy and miss my car either way.

Quote:

Originally Posted by IBill4You (Post 2247464)

Vacuum leak was ruled out by a shop. They uninstalled and reinstalled the kit to check for DIY errors, of which thankfully there were few and none that would cause this.
I'm waiting on a new tune file to verify bad tune.

I have a gut feeling it is the tune, but I know part of that is a fear of what else it could be.
If it does turn out to be the tune, I'm going to have spent more than I paid for the tune to have it diagnosed and corrected. Not happy and miss my car either way.

Was the system pressure tested by the shop? If it was not, you have not yet ruled out a vaccuum leak.

If there were a few errors on your original DIY install, there can be more that isn't immediately obvious to the shop.

have you tried resetting the ECU?

I'm still gonna go with you have a leak somewhere.

Quote:

The generic trouble code P0068 refers to an engine management problem. A disparity exists between the computer's sensors as to the volume of air entering the intake manifold.

The PCM relies on three sensors to indicate air flow volume in order to calculate fuel and timing tactics. These sensors include the mass airflow sensor, throttle position sensor and the Manifold pressure (MAP) sensor. There are many sensors on the engine however these are the three associated with this code.

Vacuum leaks are generally followed by positive fuel trims because there is extra air being introduced to the engine that the MAF doesn't know about. Negative fuel trims are more indicative of airflow being less than expected due to clogged air filters, stuck bypass valves etc...

Quote:

Originally Posted by yonson (Post 2247965)

Negative fuel trims means also fuel leak

from ur log

high pressure pump not normal
idle goes rich and normal like a waves

Quote:

Originally Posted by yonson (Post 2247965)

Pressure test -_-

Yeah, a smoke test should be the first thing performed once any forced induction system has been added...