STFT FUEL TRIMS - Explained what you need to know and Tuning info

Explained this is engine Rich/Lean o2 correction from the O2 sensors side to side- 

Do you have a smell? Poor MPG and a constant misfire and shake while driving the STFT will tell the story of where to look and what's going on 

Many people now watching TV and becoming more familiar with tuning Lingo talk about individual cylinder tuning with Timing or fuel Neither is available with the stock ECM. 

There is no reason for it to be More than 5-8% off side to side when you get those results watching fuel trims there is a Mechanical issue This is NOT something we can tune out !!!!!

Issues include 

  • Ignition misfires caused by fouled spark plug, weak ignition coil or bad spark plug wires.
  • Defective oxygen sensor or its wiring
  • Air or vacuum leaks in the intake manifold, throttle body, or in vacuum hose.
  • Clogged or unresponsive fuel injectors
  • Air getting into the exhaust manifold through a crack or gasket leak
  • Malfunctioning MAF (Mass Airflow) sensor

 

When you Start Your vehicle it runs in what's called an Open loop - It runs on the ECM tune with the basic sensors being used to start and warm up - Once it reaches the 120 range it goes to a Closed loop -

In a closed-loop system, an oxygen sensor, along the exhaust path, measures the oxygen to provide feedback regarding the air/fuel mixture and automatically adjusts the amount of fuel required for starting. As the engine temperature rises, sensors provide output to adjust the air/fuel for running. 

We as tuners can make changes based on the STFT to adjust air-fuel Rich/Lean with datalogging and to compensate for Camshaft, injectors, and Air intake changes. for a +/- swing 

We CANNOT adjust fuel side to side ( Bank 1 vs Bank 2 ) with Hptuners - so the same amount of fuel is injector in Cylinder 1 as it as Cylinder 8.  

FOR THE ONES WHO WATCH STREET OUTLAWS - THIS IS NOT HOLLEY EFI - WE CANNOT ADJUST SIDE TO SIDE - WE CANNOT ADJUST BANK TO BANK !! 

If your Car or Truck is showing +25% on the driver's side and -4% on the Passenger side then you need to look at the vehicle closer. Plugs, Wires, Fuel injectors, intake or exhaust leaks can all affect this but it's NOT THE TUNE !!! WE CAN ONLY GIVE YOU FEEDBACK TO POINT YOU IN THE DIRECTION YOU WILL HAVE TO CHECK THINGS AND USE YOUR ABILITY TO FIND AND FIX ACTUAL PROBLEMS 

 

 

 

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