GinCQ

So my new coupe has been running really lean and it gets worse as the car gets warmer. After it is fully warm it will go into limp mode. It is usually under load in 3rd gear at around 3k. I pulled the codes today and this is what I got.

2242: CO potentiometer - Output voltage too high (Poor acceleration, Poor fuel intake) Check air mass sensor.

2342: O2 Sensor. The PO used a universal sensor and the connections were coming apart

4431: ISV. This was sticking but I took it out and cleaned the solenoid. I can hear it click like the solenoid is activating, but after disconnecting the battery I am still getting the code.

Now, I just cleaned the MAF so I am guessing it is completely wasted and that code would definitely cause my lean condition. However, my question is this...in these cars (Audi) is it possible that by the O2 sensor being bad, and showing rich, the MAF is trying to lean the mixture? In theory, if the O2 sensor was giving the ecu a false signal then the MAF could lean out the mixture even though it does not need to be. I know that at WOT the O2 sensor is completely out of the equation and that is when the car feels like someone turned the pump off, but I thought I would ask since I am not familiar with how Audi has set up the system and I still dont have a manual.

2nd, does anyone have experience with universal O2 sensors? I have had plenty in the past that were supposed to be the correct part for the car, but they never seemed to work as well as spending the extra $$$ for a direct replacement. I have contacts at Woldpac and can also get the NGK's at cost so Im not too worried about it, but again I thought I would get some imput.

3rd and last, what is the proper test for ISV funtion? Or proper specs? If it all checks out, is there any way to clear the code?

Thanks for reading my CQ novel. Once I get that stuff squared away, and the car running correctly, I can tackle the nest of wires under the dash (I had to make a separate post today to find the diagnostic terminals) and maybe even get into my trunk since the key does not work and the vacuum will not unlock it anymore.

JPCady

there have been lots of discussions here about universal O2 sensors...some swear they work fine, some say no-way. I've had a universal for a couple of years now, and my coupe runs just fine, and I just got 25 mpg on a road trip.

As far as getting into your rear hatch...I've done it before. You have to crawl into the trunk through the car with a flashlight. You should be able to take off an interior panel on the inside of the passenger side taillight, and behind it, it's possible to get ahold of the actuator rod that connects to the trunk latch. I needed my brother to pull the hatch up while I worked in the trunk.

HTH
Jake

4Driver4

Your clear starting point is the 02 sensor. I am firmly in the OEM camp on this. There is no such thing as a universal O2 sensor. O2's are like spark plugs: they all look the same, but all are different. If you get lucky, the wrong plug might work Ok in the engine anyway.

OEM is teh best.

20VT90q

That and I had an MAF problem which caused the same thing. You should be able to get a used small bore MAF a lot cheaper than an 02 anyway. Check audifans.

independent77

i have a used smallbore maf if you want.

GinCQ

I have had lots of experience with cars needing a certain resistance from the O2 sensors to read correctly and even though Bosch would say it was the correct universal part # they still wouldnt work right and they would throw codes.

GinCQ

Yeah, but I thought I would ask since some systems will try to compensate. Like if the O2 sensor failed the other way showing rich and the MAF leaning out the mixture. My first guess was the MAF when I put my foot into the peddle and the car stops moving and then goes into limp mode. Im replacing them both anyway, but it never hurts to hear experience from other owners.

GinCQ

Is is the entire assembly or just the sensor? I guess all I really need is the sensor. What are you looking to get for it and would you be okay with waiting until next Thursday 7/10?

GinCQ

Is it just disconnecting the battery?

nothing

...it just happens to share the same housing as the MAF. Cleaning the MAF will have no effect whatsoever on your CO potentiometer error code.

There is nothing wrong with your MAF. Adjust the CO pot. Instructions are in the Bentley manual. It's easy to do. It's meant to be adjusted - that's why it's there!

If adjusting the CO pot does nothing, then it will have to be replaced - coincidently meaning replacing the MAF sensor as well since they share real estate.

Your biggest problem is definitely the 02 sensor, however.