Code 26, air / fuel ratio rich malfunction Options

[Bigmeanbulldog55]

I've been getting a code26 from my car. That's the rich air/fuel mixture code. I know, the 5sfe runs rich anyway, but not enough to throw a code. I know my EGR is needed cleaned. I also know that I welded close to my O2 sensor not too long ago. To stop the CEL, I unplug the O2 sensor and reset the ECU. This works, but I know it's not right. I was thinking it was either the O2 or the EGR, but when I look in the Haynes manual, it's saying: injector circuit, injector, air flow meter, cold start injector, or ECM. Anyone have any advice for me?

[Bitter]

you may have damaged the sensor, try swapping in a new one.

[Bigmeanbulldog55]

you may have damaged the sensor, try swapping in a new one.

That's what I'm betting on right now. I'm going clean the EGR and replace the O2. btw, my gas milage has went from around 30mpg to low 20's. Otherwise, I probably wouldn't do anything.

[bindertch]

Which sensor did you work near? If it was the rear then no problem. I would try cleaning the EGR out and then see. Also I wouldn't worry much about damaging the sensor it would be more likely the ECU.

This post has been edited by bindertch: Apr 4, 2007 - 7:22 AM

[Bigmeanbulldog55]

Which sensor did you work near? If it was the rear then no problem. I would try cleaning the EGR out and then see. Also I wouldn't worry much about damaging the sensor it would be more likely the ECU.

There is only one sensor on the 94 GT's, outside of Cali. It's the one in the exhaust manifold. I was welding on my header and I left the o2 sensor in while I was doing that. How could it be my ECU? I figured and ECU would just crap itself, or stay working fine, one or the other.

This post has been edited by Bigmeanbulldog55: Apr 4, 2007 - 10:39 AM

[alltracman78]

when I look in the Haynes manual, it's saying: injector circuit, injector, air flow meter, cold start injector, or ECM.

This is why Haynes is junk IMO.

Start with your O2 sensor since you were messing around it.
Also check your CSI, CSI time switch, EFI water temp sender and MAP sensor.

There is a list of things it could be, but those are the most likely.

[Bigmeanbulldog55]

Could easily be the CSI, it's had a lot of issues starting when it's cold. I don't understand how it could be the water temp sensor. I also don't understand the MAP sensor. The map just messures pressure doesn't it? I see that coming into effect if the EGR isn't working propperly.

[alltracman78]

It has nothing to do with the EGR.

The ECU is seeing a rich signal from the O2 sensor for too long.

If the MAP sensor is sending too high a pressure [more than what's actually in the engine] it will run rich.
If the EFI temp sender is telling the ECU the engine is cold it will run rich.

[bindertch]

You can only read the O2 sensor if you have a really good digital meter or if you have a graphing meter. What you would be looking for is a switch from .2V to .8V as the ECU adjusts the A/F ratio. The other two sensors can be read by using a pin slid into the back of the connector and measuring the voltage on a multimeter. Also the ECT can be read using an Ohm meter. You can read it when the engine is cold and then when it is warm looking for low resistance when hot and high resistance when cold.