tanya_charbury

My tech has for months now been chasing the rich-idle problem on my 2003 A6 Quattro 4.2 V8. When she reset the ECU, then at idle the car's fuel trim showed it's maxxed out at trying to lean the mixture out, and pretty soon the check engine light came on again. Also, at high RPM and high power the car produced an odd error message in the log. Also, there was a strong vibration when accelerating hard. We do need the front vibration dampener renewed but it shouldn't be vibrating that much.

My diligent tech has already fixed every vacuum leak so those aren't a factor either way. Today she investigated the air temperature sensor in the mass air flow sensor .... and we realized it's the wrong one. Even though visually they look the same (to me anyway) they're electronically different. Ever since I owned it, the 2003 car had part number 077133471G which is for the 1999 and early 2000 models, those with the ART variation of the engine. Some pink junkyard paint on the part suggests what likely happened: the original part had failed and the owner had replaced the part with a used part that looked like it would be a good replacement.

The car instead needed part number 077133471J which is for the late-2000-and-on models, those with the AWN variation of the engine. So my tech raided my white 2001 car, and installed its mass air flow sensor in the 2003 car.

Result: problem solved. The fuel trim is now fine at idle after an ECU reset, and the car accelerates smoothly and more powerfully, with most of the vibration gone. Yay!

S/RConcepts

I just wanted to say I really enjoy reading this thread, all of the information contained in here is invaluable to those of us with a 4.2 C5, so thank you for posting the things you come across in your travels.

After a little over a year (and I really don't want to know how many dollars I've spent), Wednesday evening I finally did the initial test-fire on my project 4.2. It was extremely successful, and I plan on posting a (large and pic-heavy) thread telling this car's story when it's a little less blown apart. Now that the big test is out of the way, I can start buttoning up the rest of it, including pulling the valve body to send to Eriksson.

tanya_charbury

@S/RConcepts That made my day. Thank you ... and congratulations!! I'm cheering you on.

tanya_charbury

Today mostly saw me getting the windshield replaced and dealing with a flat tire on my gold 2003 A6 C5 4.2 V8 (nicknamed "Nugget"), then helping my tech girl make one good 1990s Ford F-250 truck out of two, then documenting and photographing various A6 C5 4.2 V8 parts, and interviewing my tech girl about what she recently did on two of my A6 C5 4.2 V8 cars, and why she did it the way she did. She works way faster than I can write so I have to play catch-up. My focus was on the mass air flow sensor she'd removed, along with the air filter box, so I was curious as to why she did the latter. She explained that, otherwise, one of the Torx T-30 screws is hard to reach; blocked by the engine. She explained that the steps for removing the MAF are pretty much as for replacing the air filter.

The "goddamit, I broke something and now my car won't run" item on this task is to carefully unclip the thin, plastic, black coolant line that snakes behind the engine and then along the passenger side (on LHD cars), and (key issue) is attached to the air filter box, using some unusually-positioned clips. If she hadn't warned me I'd probably have broken that coolant line when removing the top of the air filter box. I'm not saying it's brittle but (unlike me, finally mellowing out) it's not likely getting better with age.

In my experience after working on Renault, Peugeot, Alfa Romeo, VW, Opel, BMW, Ford, Volvo, Jeep and Mercedes-Benz, these Audis C5 A6 4.2 V8 are shockingly easy to work on once one knows how to approach a particular task, but they are also highly non-intuitive, for me anyway. When I guess, I guess disastrously wrong. I've already bought a Bentley manual license for the A6 C5 and a couple of days ago I bought the AllData one too And then I heard that the founder of Haynes manuals (every manual based on a complete tear-down and rebuild) has passed away, dangit. I love Haynes manuals. In my dreams, there's a Haynes manual about the C5 A6 4.2 V8. Actually, In my wildest dreams, there's a Haynes manual about everything, including me. I didn't come with a manual and many days I wish I knew what to do with this complex and requires-more-maintenance-than-I-can-muster being in the mirror.

Thanks to someone super-nice, I have secured financing to buy my shop, yay!!! That's the best news I've had in the last 3 months. One of the first things I wanna do is enclose the entire parking lot. The US concept of nice cars "sleeping" outside is so culturally alien to me, and having gasoline theft and the related vandalism isn't helping my enthusiasm. One problem is that regulations on commercial building constructions & additions keep getting more draconian so I probably won't be able to afford it for several years. An interim plan is to make sort of an informal sun room, so walls and a roof but not a concrete floor. That way i can keep intruders out and in the summer, my cars won't bake in the Nevada desert heat. I love finally being able to make long-term plans, and do things that otherwise would have needed the owner's permission, not least since he's been known to say "no" on occasion. I've been trying to keep on his good side by not raising issues when I can reasonably avoid them I do the same thing with the apartment I'm renting. Bathroom fan grinding? Faucet issues? Toilet broken? Roof leaking? My policy: don't bother the landlord, just go to the hardware store and deal with it. That's why, at my shop, my guy tech showed up recently with a new (used) toilet he'd salvaged from some place for free, and he likes it being larger where, um, it matters (I gather) so at some point the old toilet in the 2nd bathroom will be replaced with the one that's right now sitting on the bathroom floor next to it. That's good because my girl tech wandered in there the other day and absent-mindedly sat down on the wrong toilet, then realized, wait, there are two side-by-side toilets here, and she figured out (soon enough) that she'd been sitting on the one that wasn't connected to anything just yet.

This ties into this past week also seeing some ancient leaking cracked plumbing pipes in my shop needing replacement. I'm friends with the owner's son so I got his OK to do the repairs and otherwise I didn't bother his dad. Another example: my shop's pit fills with water after a rainstorm. Not a problem ... it'll evaporate eventually. I'm mellow.

When it was too late to influence my approach, but not too late to vindicate it, I learned that one of the reasons the owner chose me as the buyer, and not another candidate, is that I'm super mellow to work with. So that's good. I do announce the issues so the landlord can choose to step in and do any work that might be in the "stitch in time saves nine" category but I don't insist on anything. Flying under the social-hassle radar ... it works for me. I'd rather deal with technical problems than people problems. That's probably why I like computer software engineering so much. Something is a "zero" or a "one" and it's all nice and clear. In my opinion, the best tactical conversations are sort of like an old ATM machine dialog, e.g., "Insert your card" ... then I do, then ... "whaddya want?" ... "cash" .... "how much?" ... "$100" .... "receipt?" ... "nah." Done. Clean, simple, binary. I like that. That's how I think. Kinda like that scene in Heartbreak Ridge where the guy is told everything doesn't fit so neatly into "black" and "white" and he responds with "what else is there?" -- swoon.

~T

tanya_charbury

So nowadays I can legitimately have conversations like:

- Do you have the keys to the Audi?
- Which one?
- The A6 (vs. the A8s)
- Which one?
- The 4.2 (vs. the 2.7)
- Which one?
- The gold-colored one (vs. the black, white or silver)
- Which one?
- The 2003 (vs. the 2000)
- Oh. Yes, here they are. :-)

It delights me what careful shopping will accomplish. This is like I've become a millionaire but instead of me having lots of money, the things I like have just become super-affordable. I like it.

~Tanya

tanya_charbury

I might be selling one of my Audis to my friend. He needed to borrow a car so I lent him a silver C5 A6 4.2 V8 and now he's enthused. My tech is concerned the whole fleet might vanish. In my opinion, the way to make a bunch of Audi parts have the lowest possible market price is to arrange them in the form of a running car and then sell that. Running cars seem vastly underpriced. So, I just keep buying more. Another friend had her Cadillac die and I offered to lend her my white C5 A6 4.2 V8. It's nice to have a little fleet. Ironically I didn't have an extra Audi to lend when my shop tech needed to go home in bad weather ... lousy timing on my part. I still feel weird about it. So now he bought a Subaru and maybe I could have inspired him to buy an Audi instead, dammit.

As I ponder my little fleet and its maintenance needs, I wonder if maybe I just have a knack for making really bad decisions. Here's a subset of my standard set of things I recommend attending to on a newly arrived C5 A6 4.2 V8:

-- The center part of the instrument cluster lights
-- Vacuum leaks
-- Whatever is making the check engine light go on
-- Torn engine intake runner bellows
-- Whatever is making the brake pad wear warning go on
-- Cloudy headlights
-- Bad water pipe to oil cooler
-- Front control arms
-- Lower front valve body housing pressure regulator in the transmission
-- Transmission filter, gasket, new fluid
-- Engine oil and filter
-- Coolant bottle
-- Timing belt & water pump
-- Broken front engine vibration dampener
-- Engine air filter
-- Cabin air filter
-- Broken cup holder in dash
-- Broken cup holder in center console
-- Broken Symphony CD player due to coffee shower
-- Broken trim on ashtray
-- Scratched chrome gearshift lever surround
-- Replace center console mirror switch with one made in China, then a good OEM used one
-- Front bumper ends not tucked in right
-- Front bumper nuts, three on each side, missing or replaced with something else
-- Alternator bearings
-- Front brake lines, pads and rotors
-- Whatever's wrong with the headlights: lame bulbs, broken internals etc.
-- Break in tailgate wiring harness
-- Put 60A fuse back into S42 position
-- Leaves in plenum
-- The three missing clips that should be holding the cowl water shield down
-- Center trim piece in front of one of the front seat bottoms
-- Fix the Secondary Air Injection
-- Tires, including the spare
-- Missing jack and tell everyone who uses the car that the jack's name is "widowmaker" and never to use it
-- Load up the CD changer
-- Missing wheel changing guide stud
-- Missing tow hook stud
-- Fix whichever electric fan isn't working
-- Replace the V6 windshield with the right one
-- Torn boot(s) on front drive shafts
-- Hazard switch
-- Alignment
-- Unhappy O2 sensor(s)
-- Reconnect the front fog light(s)
-- Side mirror, the one with the cracked glass
-- Non-filthy driver side sun visor
-- Hood strut. I'm sorry, I should have said that sooner. Ow. Yes, the stick sometimes slips.
-- Mechanical fan bearing
-- PCV valve
-- Battery terminals
-- The battery
-- Key fob battery
-- Broken taillight
-- Replace metal vacuum actuators with plastic ones, after they break, fix the root cause and buy new plastic ones
-- Thermostat

.... what did I overlook?

~Tanya