What happens when fuel mixture is too rich?
A fuel mixture that is rich could be the cause of rough idling. This means the vehicle will actually vibrate and feel a bit rough as the engine is running. While the car is not moving (idle), you may notice that the RPMs on the tachometer behave erratically, slightly jumping around.
What kind of fuel trim is running rich?
Okay, next issue… my car is running a little bit rich. Scanning it and reading about -8% LT when idling. When at around 25% throttle and 50kpa MAP LT fuel trim is just -1%. Pressing the throttle a little bit more and at higher MAP I get -4% to -8%. Values are not that much off so the check engine lights is not on and no DTC thrown.
When to take a long term fuel trim?
Note also that fuel trim values should only be taken when the engine had been running at the above speeds for at least 30 seconds. Ideally, long-term fuel trims should be at, or close to 0% when the engine is running at a steady speed.
What causes fuel trim values to be off?
However, even if the sensors are known to be good, it can happen that displayed fuel trim values may be off by as much as 20% or more; this can be the result of a malfunction, or, it can be the result of someone having recently cleared all fault codes.
Do you smell rich fuel in the idle?
Idle seems off even for the cam and it smells really rich. I have my tune and logs. I would really really appreciate it if someone took at look and provided me feedback. There is no guessing with this stuff, it’s either right or it’s wrong. Your log shows that the fuel trims are pulling fuel, so yes it’s rich.
What does it mean when your fuel trim is negative?
Rich codes and the drivability issues that accompany a rich running condition would be reflected with negative fuel trim numbers: an indication the PCM is subtracting fuel. Leaking injectors, broken fuel pressure diagrams, improper fuel pressure and skewed sensor readings are a few examples of issues that could result in a rich running condition.
What causes a + 13% long term fuel trim?
In this example we’ll examine the possible causes of a +13% long term fuel trim. What the LTFT is telling us is that it has to continuously add 13% more fuel. In other words, the engine is running too lean and the PCM/ECM is forced to compensate by adding more fuel. • Restricted fuel system.
Is there such a thing as a 0% fuel trim?
While fuel trim values of 0% would be ideal, there is no such thing as a perfect engine, which means that in practice, achieving 0% fuel trim values consistently gets progressively more difficult as an engine ages.
Where does the fuel trim information come from?
This historical information gathered from the STFT information is stored in a data file system known as fuel trim cells. These cells hold fuel trim information over a wide range of rpm’s and engine loads and are used by the PCM to make quick decisions when the engine load changes.