2001S4

I just posted a message comparing my '01 S4 to a new S4. Surprising (to me, anyway)I did not like the new S4. Too heavy and numb.

Anyway, the reason I was looking was my check engine light came on. It has 130K miles and a manual gearbox. Codes were misfire, oxygen sensors, Exh gas temp sensors, cats. The sensors are all original,maybe I changed one several years ago. Cats are original, Plugs had too may miles at 80K. So I replaced the plugs, hoping to cure the misfire which might make averything else happy. No good. Codes came back, except the misfire. Engine is running well, and idles smoothly. Does not burn oil except for cam adjuster seals which leak despite repair. The rings and valve seals seem to be fine.

To replace all sensors and the cats will cost over $5K, This is approaching the value of the car, and I am hesitant to drop that amount of cash when there are still 2 original turbos and a clutch with 130K miles on it.

So, what is the collective experience with these codes? Can I just change the oxy sensors and is that likely to fix the problem? Or am I really going to have to replace the cars at $1500 each plus labor, tax? The Exh temp sensors are also very expensive, do these typically need replacement at this time too?

-Tony

Flyboy

I would start by replacing the O2 sensors, between them, EGT's and cats the O2 sensors seem like the most prone to failure. If you're trying to be cheap about it you could check the classifieds on the various Audi forums for somebody parting out a car and see if they have O2 sensors for sale. You may find EGT sensors that way as well, but I'd hold off on those until the O2 sensors were replaced and you see how the codes look.

I'd be a bit surprised if the catalytic converters were bad, 130k is not that many miles, probably close or a little less than average for these cars. Again, people can be found parting out cars and have used ones available.

My guess is that worst case if all those things did need to be replaced you could source used parts and get it done for under $1,000.

shawnoc2003

If you even consider replacing the factory cats, you might as well just install aftermarket down-pipes w/ cats. The engine spools better without the pre-cats and sounds a lot better.

Change the front two oxygen sensors first - should be ~$300 for both + $50 for a long 1/2 extension bar + $35 for an O2 sensor socket if you don't already have them.

Since you don't like the new S4 (understandable given the money), you might as well start modding your current one. I've got 270,000 on mine and its still going strong.

shawnoc2003

BTW: don't worry about the EGT sensors - you don't need them for the street.

Flyboy

Also budget for a new tune if eliminating the pre-cats.

2001S4

A friend said I could take this opportunity to upgrade the entire exhaust system to RS4 specs and get another 150 hp out of it. I am a little wary of this on a 130K mile engine.... Overstress::bearing and ring failure.

I like the idea of just doing the oxy sensors alone. I suspect that the computer saying that the cats are bad is due to bad readings from the oxy sensors. Is there any other way the computer identifies a cat problem?

My main concern is that I will be dying the death of 1000 cuts. $800 here for the sensors, $1k there for rebushing something on the suspension later on this year, then $800 later on for the EGT sensors, the front door speaker has a buzz for another $100, the drivers seat leather has a small rip and it might be replaced for $300. Then after all that, I can foresee the clutch or turbos give up and need replacement. I could easily gradually invest more than any possible resale value in the next 2 years.

The flip side of this is that a new-to-me used car could easily cost $600/month. If I were to earmark that $ for maintenance on this car, then I could keep it maintained for a long time....

(Also, I have to pull the instrument cluster to have the center display repaired....)

Still weighing my options..... None of the cars I might get to replace the S4 have the personality of this one.

-Tony

Flyboy

Your friend is mistaken. Optimistically you might get a third of that, probably less though.


O2 sensors are not $800.

This is from an ad on Fortitude:

"front and rear 02 sensors 50 shipped each
egt sensors 100 shipped each (black and brown boxes available)"

You can get a full set of brand new O2 sensors for under $500. A lot of these parts once you replace them that would probably be the last time you ever had to do that. Sure, parts eventually wear out, but the cost to maintain the car pales in comparison to what it would cost for a new one, and then wrap in the depreciation of that newer car, plus possibly higher insurance costs.

shawnoc2003

Module master for the cluster repair -$150

Don't do RS4 exhaust - go awe, miltec....etc. or some other aftermarket units.

As for mileage, I bought mine with 100k on the odo., chipped it and put on an exhaust when I bought. I've got 270k on the odo now.

As for required maintenance:

Clutch at 165k -approx $1000 with aluminum flywheel
Coil overs at 165k -$1200
New suspension (bushings and control arms) at 180k - $750


At 270k the original turbos are getting weak so I'll probably upgrade to the k04 or rs6 turbos soon.. Point being, the engine is pretty reliable so change the oil every 5000 miles and enjoy. Keep searching the forums, sounds like your getting some bad info.