February 28, 2021

10K Pot Mod- By [SPOOLIGAN]

Many of us 2G guys like to put a 1G CAS in our 2G’s. Whether it be due to the fact that the 1G CAS is adjustable or for the simplicity of replacing the CAS. Especially the 2Ga guys that don’t have a CAS on the head at all.

This can be done, but I can pretty much guarantee you will be scratching your head after a while of driving like this.

With the 1G CAS on a 2G, you COULD have a random misfire issue. While cruising, you will get this misfire. It will feel like you are on 3 cylinders. To remedy this, you need to prevent the ECU from checking for random misfires.

This is a list of criteria that your ECU needs to see in order to not scan for misfires.

  • 300+ seconds of steady state RPM less than 80% throttle position
  • Engine coolant temperature -10C or higher
  • Intake air temperature -10C or higher
  • Barometric pressure greater than 76 kPa

So, if we can get one of these values outside of the criteria, the ECU won’t check for misfires.

Logically, the barometric pressure is really the only one from this list that can be altered without creating more problems.

The fix? The 10K Potentiometer Mod (10K Pot Mod). The Potentiometer is just a volume control knob and can be purchased at Radio Shack for just a few bucks.

You wire the Potentiometer into your barometric pressure sensor wire in your ECU harness. With the potentiometer turned up, it will change the resistance of the wire thus tricking your ECU into thinking you are on Mt. Everest. So, the ECU will not scan for any misfires.

The Pot Mod will generally lean the car out slightly. Which means you MAY feel a performance increase (if I did, it wasn’t much).

  • Here is what all you need:
    10K Potentiometer (as stated, this can be found at Radio Shack. Tell them you need a volume control knob because they may not know what a potentiometer is. Also, get the bigger one that is easy to adjust.)
  • Wire Strippers
  • Soldering Iron
  • Wire (approximately 2-4 ft.)
  • Electrical Tape

Step 1) Remove the access panel so you can get to your ECU.

Step 2) Pull out the top plug (will be the hardest to reach)

Step 3) Find wire #85 (orange with a white stripe) (Barometric Pressure Sensor)

Step 4) Double check the diagram below and make damn sure you found the right wire. Once you verify that it is the correct wire, cut it about 6″- 8″ from the plug.

Step 5)
Solder one end of the wire you just cut to the center peg of your Potentiometer (this is where you can use the wire that I suggested in the parts list. Wire length depends on where and IF you want to mount the Potentiometer).

Step 6) Solder the other end to the left or right peg of your Potentiometer (doesn’t matter which)

Step 7) Turn the Potentiometer OFF (counter-clockwise)

Step 8- Plug the harness back into the ECU and start the car.

Your car should idle the same as it did before. If it is real choppy, you may have your Potentiometer turned the wrong way.

Take your car for a drive. You need to be at cruising speeds (55+MPH). Once the misfire occurs, turn the Potentiometer up a little bit. If it misfires again, turn it up more. Repeat this process until you no longer encounter the misfire AND your CEL goes away (if you have one now that you did not have before the Pot Mod).