High fuel trims that get worse at higher RPMs
High short and long-term fuel trims that worsen at higher RPMs point to a fuel delivery issue rather than unmetered air. People often hit a diagnostic dead end trying to fix lean codes because standard checks on vacuum lines, O2 sensors, and EVAP systems show no faults. Locating the actual problem requires measuring fuel pressure to test the pump and injectors directly.
What people tried
Every workaround mentioned in the threads below. We haven’t tested any of them — and nobody here is claiming they worked.
Found another way around this?
Share your steps and trade-offs so fellow engineers don't have to reinvent the wheel. No account required.
- 1Spraying brake cleaner around a running engine to check for leaksDid this help you?
- 2Resetting long-term fuel trims periodicallyDid this help you?
- 3Pinching off the evap line to the intake to check if trims dropDid this help you?
- 4Swapping the entire fuel rail and injectors with spare parts.Did this help you?
- 5Figuring out a way to attach a pressure gauge on the fuel line to test pressure under load.Did this help you?
In their words
Unedited, grouped by where they were said, most upvoted first within each place, each linked to the thread it came from.
“what’s the problem here? o2 sensors seems fine , fuel pump works and filter is clean, coils,plugs are ok injectors are working. …. evap is ok too”source ↗
“trims get worse at higher rpms …. and yes both short and long term trims are high”source ↗
“my suspicion is on injector/ and fuel pump….. will measure pressure and see”source ↗
Where this came up
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