What should fuel trim numbers be for engine misfire?
Short-term fuel trim (SFT) numbers can be used to determine if the misfire is caused by lean or rich a/f ratios. Normal SFTs running about plus or minus 5%, or even as high as 10%, might not indicate a problem.
What does it mean when a cylinder is misfired?
If your scan tool’s misfire history indicates multiple cylinder misfires, focus on the cylinder with the most misfire counts. The misfire counts on adjacent cylinders are often “sympathetic” misfires that will often disappear when the primary misfire is repaired.
What should the short term fuel trim range be?
Short Term Fuel Trim. • This is an immediate correction to the fuel systemto the fuel system • An acceptable range is +/- 10%. Long Term Fuel Trim. • This is how the system has a tendency to runtendency to run • An acceptable range is +/- 10%.
How to diagnose an intermittent engine misfire?
When diagnosing intermittent misfires, don’t forget to look at pending codes for indications of an individual cylinder misfire. If your scan tool’s misfire history indicates multiple cylinder misfires, focus on the cylinder with the most misfire counts.
Can a negative fuel trim cause a misfire?
The O2 sensor will read this as rich, and the computer will lean out the mixture (causing negative fuel trim) to compensate. An excessively lean mixture can cause misfires. Make sure you have spark and the plugs are good.
What should bank 1 fuel trim be at idle?
If long-term fuel trim (LTFT) for bank 1 is 25% at idle, but corrects to 4% at 1,500 and 2,500 rpm, focus on factors that cause a lean condition at idle, such as a vacuum leak.
When to use fuel trim to identify a problem?
Fuel trim can also be used to identify which bank of cylinders is causing a problem. If the LTFT for bank 1 is 20% and the LTFT for bank 2 is 3%, the source of the problem is associated with bank 1 cylinders only.
Where can I get short term fuel trim?
Fuel Trim download can be obtained atFuel Trim download can be obtained at www atechtraining comwww.atechtraining.com Short Term Fuel Trim • This is an immediate correction to the fuel systemto the fuel system • An acceptable range is +/- 10% Long Term Fuel Trim