Skip the auto shop - Our mechanics make house calls

Q: Short-term fuel trim swinging plus or minus 10% during driving

asked by on

Is it normal for a short-term fuel trim to swing plus or minus 10% during driving? It happens during every acceleration and deceleration. I've got a new car as my last one had a bad engine.

Yes, this is normal when you accelerate and decelerate. Your vehicle will add fuel at times, and when you take your foot off the gas, it will subtract. This is normal for any vehicle, even my Toyota does this. Once you’re at a steady speed, the trim will usually be around plus or minus 1% to 2%, at 36,000 miles.

It’s the opposite when accelerating and decelerating in short periods, the short-term fuel trim will go up and down more noticeably. That’s why it’s called short-term fuel trim. The more important data to observe is analyzing the long-term fuel trim over time. That gives you a better idea of the overall health of your engine and your fuel injection system.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!

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

Q: What does the AVG MPG feature in the message center mean?

Ever wonder just how good your car’s fuel economy is? Have you tried to measure it using math on your own? If so, you’ve likely found that your results don’t match up with how much gas your car burns on...

Q: Knocking sound when driving. Disasters when braking or accelerating.

If the knocking only appears when you are at cruise and becomes more frequent as you go faster, then you may have an axle inner joint or a transmission mount or engine mount issue. This may be why the noise...

Q: Recently my 2011 Kia optima ex GDI turbo has begun to decelerate when going uphill. The check engine light has been lit up for a month.

Hi there. Sounds like the turbo is not functioning correctly. The turbo may have a broken shaft or the intake fans are broke. When the turbo is not working, then the engine will not accelerate properly, especially under a load....

Related articles

P0052 OBD-II Trouble Code: HO2S Heater Control Circuit High (Bank 2 Sensor 1)
P0052 code definition HO2S Heater Control Circuit High (Bank 2 Sensor 1) What the...
P0240 OBD-II Trouble Code: Turbocharger Boost Sensor B Circuit Range/Performance
P0240 code definition Turbocharger Boost Sensor B Circuit Range/Performance What the P0240 code means P0240 is an OBD-II generic code triggered when the Engine Control Module (ECM) detects the intake boost...
How to Avoid Back Pain in a Car
If you have back problems, sitting in a car for an extended period of time can be excruciating. Even without back problems, you could experience discomfort and soreness from...