Well about a week ago I installed an air/fuel ratio gauge in my Max. I figured that if anything, the gauge would read rich all the time because I have horrible MPG. Well, I have no idea what to think, because the gauge goes crazy, it never stays in one area, in fact most of the time its lean (like when stopped or idling). When I floor it, it read rich, but doesnt stay there, it will jump between lean and rich all the time and very quickly. It is rarely in the middle (stoich). Does this mean that my O2 sensor is bad/malfunctioning? I dont have a CEL going off, but if it was bad, it would explain the horrible mpg and bad engine performance, right? Let me know thanks!

Devon

P.S.- I looked at my friends car which has a air/fuel ratio gauge and its always in the stoich area (unless when flooring it or shifitng gears). I have an auto so im not sure if that matters.

 

Anyone? =(

 

sorry i can't help ya there. I think it SOUNDS like it could be O2 sensors cuz that is what the max uses to adjust the air/fuel mixture ratio. If this is continuously varying, that could be the prob. Ar you sure your guage is installed properly? might wanna re-check that first.
As for the bad performance/mpg, it could be a few different things. Knock sensor, O2 (probably), fuel filter, or maybe a really dirty MAF. You could try cleaning your MAF with a q-tip and some rubbing alcohol, give the ecu a few hundred miles and see what happens.

 

Where did you tab your wiring for the gauge at?

 

thanks for the input.

All i get is the KS code (ghost code), but i tested the KS and its fine, so something is tripping it. Im going to clean the MAF tomorrow. Filter is good, and im thinking of changing my O2 sensors (2 front) since my car just hit 100k the other day and I think they are the ones that came with the car =X

 

If i remember correctly, it was the white wire (middle one). Im pretty sure its the right one, cause when im in nuetral or in park, and i press the gas...the gauge read lean then to rich...but then back to lean (it moves with the way i push the pedal).

 

Sorry I didnt specify, I meant where did you tap..The ECU, Front Oxygen Sensor, Rear o2? Thats what I meant, sorry for the confusion.

 

i tapped the fron o2 sensor...the one that is in front of the fans...

 

According to the FSM, the front O2 sensor is going to be rapidly switching A/F ratios with the ideal ratio being during the radical change from 1v to 0v. The rear O2 sensor has a much longer switching time between rich and lean than the front O2 sensor. Also, under normal operating conditions, the rear O2 sensor is not used for engine control operation.
Based on this, I would think the rear O2 sensor would be a better one to tap into for a gauge. The front seems to be constantly switching at a fast rate, which could definitely give the symptoms you described. I would try tapping the rear sensor before spending money on parts or labor you may not need. Worse case scenario would be that it doesn't solve your problem, and you are out $0.00 plus a little time.
Just my thoughts.

Dave

 

Good idea, thanks. My car hit 100k the other day, and i think that the o2 sensors are the ones that came with the car, should I replace them due to the fact that they have more than 100k miles on them??

 

If you're not getting a code for them, and the car runs good, I'd leave them. You could remove and clean them, but I wouldn't spend the cash replacing a good part (unless of course you have so much money that it doesn't matter and you want peace of mind). There's a post on here about cleaning them. Basically you remove them and spray with carb/tb cleaner.
I've looked at mine, contemplating the cleaning process. They look like fun to remove. Mine will stay in till they go out.

Dave

 

I see...well, my car is runnign liek crap. Im getting an average of 12mpg, and car is peformaing as well as it should, The only code I actually have gotten is for the rear heated o2 sensor, i got it twice a few months ago, hasnt come back.