power6

I have a 1998.5 v6 quattro that has had the CEL on forever now, and Im at 110,000 miles or so. I had the light turned off at autozone after it showed 2 codes, think they were 1157 and 1159, or something like that, but it was a lean condition on both banks. I checked the fuel pressure and replaced the filter. 500 miles or so later, light came back. Now, few thousand miles later, car doesnt want to idle. It will shudder and stop. Im looking into replaceing o2 sensor(s) but im having a hard time finding posts about doing so on this particular motor. How many are there? Which ones are probably bad? Can I use the cheaper 3 wire (about $75 online) and splice?? any help appreciated.
-Dave

Kris Hansen

I would check the throttle body, give it a good cleaning. THere is a TSB on it, don't have it offhand, but basically you remove the plastic boot to the TB and clean the throttle plate with carb cleaner and a rag.

Also, how new are your plugs and wires?

to answer your question, there a 4 O2 sensors, 1 before each cat, and 1 after each cat.

AudiMick

Rears are different (sensor is the same but wiring is different).They are all four wire. I don't think you can use 3 wire sensors.The post cat sensors are heated.
These thing are expensive. Buy or borrow an OBD tool and check which one is bad if at all.I have the shareware version of Ross-tech which diagnosed my O2 problem . Costs $70 at OBDtool.com including adapter. Otherwise you could spend $400-500 just experimenting. Removing the post cat sensors is also a major PITA.

power6

plugs are almost new, wires original. Thanks for all help