Q: Positive long term fuel trim.

asked by on March 13, 2017

Checked long term fuel trims at idle and bank 1 was steady at 4.7 while bank 2 was steady at 3.1 what do these numbers tell me? What should i check?

My car has 165000 miles.
My car has an automatic transmission.

The fuel trim numbers mean that the fuel is leaned out. If the number is at 0, then there is no change. If the numbers go to a positive increase, then the fuel system is leaning out. If the numbers go to a negative decrease, then the fuel system is becoming rich. Lean conditions will cause the engine’s temperature to rise and could be caused by either a loss of fuel pressure or the injectors are not spraying properly. A rich condition will cause the engine to run with a hesitation or have a nasty smell at the tailpipe and could be caused by spark plugs that are fouled out, a fuel injector that is leaking, or a fuel pressure regulator is stuck on high pressure. If you need further assistance with the fuel trim, then seek out a professional, such as one from Your Mechanic, to help you.

Was this answer helpful?
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Active Body Control problem

Hi. It sounds like there was a small leak in the system that has turned into a bigger one, and now the system can't hold any pressure at all. Typically, there will be puddles of hydraulic fluid leaking from the...

Spongy brake pedal

The brake master cylinder is most likely leaking internally; it needs to be tested, replaced then bled out of air. If the system fluid is not low, then this is the most likely cause. I recommend that you have a...

Truck overheating coolant not cycling throughout engine. 2002 Chevrolet Silverado

Hey there, thanks for writing in. You need to make sure all the air was purged out of the cooling system. If you did not get at least 2 gallons of coolant mix in the engine, then you may have...

Related articles

Which Type (Octane) of Gas Is Recommended for My Car?
When When someone pulls up to a gas station, the first thing they’ll see is the big sign lit up with the prices for the different grades of gasoline. There’s regular, premium, super, and a number of other variations of...
How Does a Fuel Injection Flush Work?
Fuel Fuel injectors, as their name implies, are responsible for getting fuel into the engine. Fuel injection systems either work via a throttle body containing as few as 2 injectors, or go straight into the port with one injector per...
How Does My Gas Tank Know When It’s Full?
Anyone Anyone who has ever filled up a gas tank has experienced the tactile "clunk" the nozzle makes when the fuel tank is full. This sound comes from the nozzle right when the flow of fuel stops. Most people barely...