Code 25 Air/fuel ratio Lean?

Tiny
TOYOTA93
  • MEMBER
  • 1993 TOYOTA COROLLA
  • 1.6L
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 140,000 MILES
Code 25 Air/fuel ratio Lean showing up, how could I fix it?
Friday, June 7th, 2024 AT 8:12 PM

1 Reply

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,582 POSTS
Hi,

A lean fuel mixture can be caused by a few different things. First and most commonly, an engine vacuum leak. If there is a leak, it allows unmetered air to get into the combustion chamber and causes a lean fuel mixture.

Next, if there is an exhaust leak before the O2 sensors, that can also cause it. The other common cause is a weak fuel pump or restricted filter.

Start by checking for a leak.

here is a link that explains how to do it:

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

Try that and let me know what you find.

Take care,

Joe

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Friday, June 7th, 2024 AT 9:06 PM

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