Hesitation when accelerating, code P0171?

STUXNET97

MEMBER
2002 HYUNDAI SONATA
2.4L
4 CYL
2WD
AUTOMATIC
135 MILES

The vehicle works perfect, but when accelerating it has a delay of approximately one second.

In other words, I have to press the accelerator almost to the bottom to have a good response.

I share some data.

I want to share other information, with a cold air intake the fuel trim goes up to 19.53. I have re-positioned the stock, and I have a better performance in "low RPM".

I should change:
-Sensor MAF (is new but not OEM).
-Sensor O2 (I have never changed it).
-Fuel pump?

I will be taking the car to a workshop to measure the fuel pressure and share the data.
I await your response, Thanks!

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3 Replies

DANNY L

MECHANIC
5,648 POSTS

Hello, I am Danny.

Since your bank 1 is running lean and your short term fuel trim is adding fuel, it sounds like you might have an intake manifold leak. You can spray around the gasket area with starting fluid and see if the RPM's increase to see if/where leaking. Hope this helps and let us know when your vehicle returns from the shop with any new information. Thanks for using 2Carpros.
Danny-

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Thursday, July 12th, 2018 AT 1:19 AM

STUXNET97

MEMBER
11 POSTS

In my country I ca not get the starting fluid, it is also dangerous to start spraying on the engine running, right?

Is there another way to find the leak?
I will be dismantling the stock air intake to review it in detail.

Also, I want to check the fuel pressure, do you know the proper values or data of this car?

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Thursday, July 12th, 2018 AT 6:12 AM

DANNY L

MECHANIC
5,648 POSTS

Hello again,

No, you can spray anything flammable because when finding an intake manifold leak on the engine (not cold air intake) it will get sucked into the engine and you will hear the RPM's change verifying where the leak is. The fuel pressure should be 37 PSI. Hope this helps and ask any questions if needed. Thanks again for using 2CarPros.
Danny-

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Thursday, July 12th, 2018 AT 5:10 PM