Disclaimer: The instructions below are what I did to my car and can be used as a "guide" for working on yours. But, I take no responsibility for what you decide to do to your car. Be sure to read through all of the instructions first before doing anything to your vehicle.

Purpose: Gives you a quick visual display of your air/fuel ratio so you know if your engine is running rich or lean.

Application: Pretty much any car with an O2 sensor.

Time Required: ~3 hr

Scale of Difficulty: 4 (5 being the hardest) Electrical knowledge helps

Cost: ~$10

Tools Required:

• Soldering Iron, Solder
• Circuit Board ($2)
• (2) LM319-N1 (free)
• 5v Regulator
• (2) 10k potentiometers
• 10-seg LED Bar Graph or 10 LEDs ($2-$5)
• 18ga wire

Here's the schematic:

The top part is for a Volt Meter and the bottom portion is for the Air/Fuel Meter.

1.

Here's some more ideas of what you can make it look like:

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