At 5am friday morning, I start the car, move 'bout 100 ft and remember I forgot something in my apt. So I park the car and leave it running. I come outside after less than a minute to find my RPMs running low (like 500 or so) and the engine sounded like it was starting to stumble. Also, the tach was fluctuating. I rev the engine a lil, and it goes away. I then look at my A/F meter. It's reading a steady RICH (blue LED glowing bright) and didn't move... i.e. no dithering back and forth. This was when the car would be idling, or moving along in 1st gear without touching the throttle. If I blipped the throttle it would dither kinda, and then go back to rich. Outside temp was mid 40s to low 50s.

I've experienced this with the car cold (that morning) and while warm ('bout 18 miles into a 22 mile commute)... also at idle when sitting in traffic trying to go through the downtown tunnel to get to work. Only, the meter would read steady green instead of rich, but still at idle. It didn't happen all the time, but I'm starting to notice it more and more the cooler it gets outside.

Anyone have any ideas? I'm unfortunately thinking that after 102k, my O2 sensors are starting to show their years/mileage (yes they're original)... but other than that, anything else that might cause it? maybe my S3 silicone hose kit miraculously started making my car run rich ;)

Thanks for the help guys. Also looks like I'm gonna be pulling my IM sooner than I thought. Valley pan gasket is DEF leaking on my car! 'Burned' half a quart of oil in less than 1k... which isn't 'that' much in Audi's mind, but more than it did the entire time at the glen, and for teh 2k of driving I did afterwards. I took a gander undre the IM and saw shiny slimy stuff looking back at me :-\. Looks like I'm gonna need to to get the remainder of the P&P tools to start/finish my IM so I can kill 2 birds with 1 stone ;) Maybe 3... I'll clean up the intakes on the heads while the car is apart as well... hmmm the possibilities ;)

by the way i had a BLAST at the track this weekend loved the pagid blues too not a single bit of fade either day though i bled the brakes before the second day which was such an improvement in the first run from the last run on saturday..!!! WOW what FUN!!!! i have a ton a pics that i will post as soon as i get a min

I think that is responsible for letting the ECU know when the pedal is floored so it knows when to be in Open Loop vs. Closed Loop.

However, after 102k, your O2's are a likely suspect, too, and should be replaced anyway.

another one is the ECT sensor which when it goes bad defaults to it's coldest temp setting. That in turn fools the car into thinking its 20*F outside and it richens the car up so it will idle. But when its not "really" that cold out it floods the car with gas. Same principle as pulling the choke lever on rec vehicles, lawnmower or motorcycle when they're already running.

There's another dozen or so things it "could" be but these two are the most likely suspects and I wouldnt look at anything beyond them until or after you've eliminated these.

If its only in one bank it's likely O2 sensor if it's in both banks I would look at ECT. If you have your A/F meter wired thru an A/B switch you can easily check both banks. If it's just in one I would swap sensors around and see if the situation continues. Or an easier, less labor intensive method would be to install a "t-tap" connector into the opposite sensor signal wire then switch your F/A monitor lead wire to that one. If that resolves it then its O2 sensor-related, if not I'll put money on ECT. Your mileage indicates you're prime pickings for either/both.

but why are you pissed now?

thats what the young techs at Champagne and the guys on the racing team have nick-named the new car.

I've read that if you turn the key and let it sit the car self adjusts it... but I'm not sure. That a VAG-COm thing? With the non-registered version allow me to do this?

Thanks,

So that might be something I'll look into more. I got kinda lucky when I clamped onto the one I'm currently using for my ARM1 =P.

For an A/B switch I'd just have to tap those 2 wires into one switch right? THen toggle it back and forth? Need to refresh my electrical switch knowledge ;) Also, I gotta figure out which 'green' wire is the other O2 sensor... lol.

As for the ECT, wouldn't that also throw off my temp gauge in the car if it were going south? Or am I misunderstanding its purpose in the car.

It makes sense that if the car were running rich, it would cause the engine to stumble... but none of this has affected my MPG, which is something I'd relate with the car running rich. It's sticking at a constant 20-25 mpg depending on what kinda traffic conditions I'm driving in (i.e. driving to work, or taking road trip to PA)

I guess my biggest issue is that I don't want to pony up the $250 right now to redo O2 sensors :-\. I'd much rather put that towards my P&P tools... hehe. Not to mention I've spent way to much on this car this year... gotta actually set myself up a legit budget next year to keep myself under control ;)

while also getting help from Mance and Mr D. Hardest part of it was trying to figure out what 'green' wire to tap, since there were 30 of them in there, and all of a slightly different shade of green from the other. Not fun to play with. Got lucky on the first try though ;)

The other hard part was mounting the lil sucker, but I kinda went above and beyond the call of duty to install my A/F meter. I made my own mount outta wood, then covered it with tinted plexiglass. Real clean looking though... to the point that people are curious why my car came with the 'KIT' voice kit in it ;)

Glad you enjoyed the track event... they're a real blast. I'm kinda looking forward to killing off my pagid blacks so I can get the blues back in ;) All in due time though.

if this problem just started this morning you likely havent had enough time to notice any reduced mpg

Only two other wires can be the correct one and if you guess wrong you'll know immedaitely by no signal to the ARM. If that happens remove the tap and place it on the other green wire. 2 minutes tops once in there!

If you do an A/B switch its as you suggested. Just a toggle switch (or similar) with one sensor connected to eac side.

I'm sorry that the answers provided may cost $250. I dont know of any way to answer the question that avoids the possibility. I look at O2 sensors as cheap. They cost less than 5 fill-ups at the gas station and last longer than 226 full tanks of gas. Pro-rated thats 18 cents per tank of gas at your mpg. We pay more than that for oil changes, tires, brakes. In fact windshield washer fluid is about the only consumeable item that comes close when pro-rated!! And if there's anything my advanced years may help you see its that there will never be a "good" or convenient time for flat tires, blowouts, dead batteries or $250 repair bills. This much I know to be true!

PS: rationalization is a wonderful thing ;-)

one is a bit more difficult to see. Tho it is discernable/distinguishable with good lighting. There's no other options in that harness and as I said above if you guess wrong just remove the tap and apply it to (at that point) the "only" remaining "all green" wire in that group.

I'd look at replacing your O2 sensors, first, since they are so old anyway (start the the two precat sensors) and see if that helps.

room in my pic poster. shoot me an email and remind me and I'll send them to ya.

they're really hard to tell apart though, that's for sure. I'll play with them more when I get the time.

thanks for that lil reality check.

It started doing this a few weeks ago. I noticed it right before I made a 700 mile round trip. And I got pretty much teh same mileage I got last weekend, and a month prior to that weekend. But then again, if the O2 sensors are shot, they've been shot for a while, and that would explain why I can't get the 25-28 mpg I used to get every once and again. Of course in my 3 years of driving this car, and my dad's 6 years of driving this car... I was the only one to hit 28 mpg =P

And speaking of windshield washer fluid... that's another thing that broke I think :(. I went to wash my windows after getting spritzed on and got nothing... nothing to the headlights either. I'm hoping the tank is just empty, but I'm not getting an idiot light telling me it's empty. Do we have one on our cars? If not I got a hunch my washer fluid pump is kaputzki. That's one thing I'd need to fix before winter...

I've done it several times.

The pump for the windshield is on the side of the tank facing the fender. The pump you can see with the hood up is for the headlight washers. I don't know how hard the windshield pump will be to replace. I just recall seeing it when I did my timing belt.

in the engine compartment. On my 90 the wires were long engough to take the left side sensor's plug to the right side's socket and vice versa. Since the sensor's read almost the same thing when they are OK and since the engine behaves about the same when one is sick, I tried switching them. Engine ran the same, readings were the same- with new O2 sensors.

Anyway, this may be easier than wiring in a switch if your goal is to determine if one sensor is out of whack with the other.

I noticed today that the car didn't run funny at all, and dithered like it was suppose to.

I'm thinking that Mance is onto something with the ECT sensor to be honest with you. Temperature was in the mid to upper 50s this morning... so tis very possible that it's the problem