Troubleshooting 2ZZ crazy high negative LTFT at idle (-28)

Started by JB21, January 21, 2024, 13:18

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Those guys seem to have greatly confused the issue. You have negative fuel trims. Generally it is correct that most aftermarket intakes that are 2.75 are larger than stock and do not have vanes which results in positive fuel trims due to unmetered air, not negative. Same with a vacuum leak.
What causes negative fuel trims is an air restriction, too much fuel pressure and restrictions from the exhaust. You need to look at these causes.


Try a new MAF just to rule it out if it hasn't been replaced recently.


Guessing you've had the same MAF pipe prior to this issue raising its head? If so I doubt it's that, maybe the MAF itself? Is the problem only at idle?