stupid939

I've been lurking for several years now, and I'll admit defeat this time! This is a two part question...

History (if you care):
I bought two Audi A6's several years ago, one with significant rear passenger damage, and one as a parts car. I replaced the inner and outer rear quarter, painted it, did a timing belt/water pump change, replaced an exhaust flex joint, and too many other things to list. This is a project car for me, but I want it to be running again!

Question 1:
The car (2001 Audi A6 2.8L) has been sitting for about a year waiting for a new battery, and I finally got one. Installed it, and the car revs up to about 1200 RPM and dies immediately. Nothing (that I know of) has changed in the last year, so I'm not sure what it could be. I changed the fuel filter (it was time) and attempted to siphon the gas (in case it was bad or if I put the wrong octane in it) but it was tough getting the hose down that bladder. This leads me to believe there is an issue with the car getting the right fuel/air mixture. It is not throwing any codes...

Question 2:
The reason the car has been sitting for a year is that it has some vibration problems. When I initially fixed it (wasn't really driveable prior) the rear passenger quarter (previous owner had hit a post) would shake at about 25 and 60 mph. It was temporary as I would accelerate, so I pushed off fixing it until... It started shaking really bad at any speed. I had to drive at about 5 mph to get it home (not far hopefully). It has been in my garage ever since. I jacked it up and couldn't feel any play in the wheel I suspect, so I ruled out a bad wheel bearing (could be wrong). I was going to take it somewhere to have someone take a look then fix it myself (as I have a parts car), but thought I'd ask the pros first!

I should also mention that there was some chassis damage by the rear wheel, but the prior owner used a flange bender to correct the problem (or so he said). There didn't seem to be any problems when I tore it down (pic attached).

By the way, I'm not even a car guy, I just dabble and happen to be mechanically inclined.

Thanks in advance!

devinsixtyseven

"Not a car guy"...jesus, man...I'd like to see that project car if you *were* .

Q2: Check both rear CV axles, rear diff mount bushings, and any intermediate support bearings on the driveshaft up to the center diff. Probably just a CV joint.

Just Me

yea, more basically you need to walk through things logically. Low speed vibrations will likely mean something loose - suspension, control arm, CV, drive-shaft. Possibly even something somewhat seized. or something out of round ( tire that sat)

As to the not revving, have you checked the fuel pump?measured fuel flow to an injector?

Good luck,

G

twentysevenlitres

I agree that the vibration is likely a CV joint. The grease on these can dry out and create lumps which can get pulled into the joint. The inners are particularly susceptible to this due to the plunging design of the joint.
A repack sorts them usually.

Start and immediate stall is classic immobiliser behaviour.
Do you have a flashing yellow symbol in the speedo or tacho (looks like a car with a giant key in its back)?
Did you change the dash over at any time? Or change keys?
The components involved are the transponder in the key (not the remote) energising coil in the black plastic surround of the ignition barrel, and the immobiliser incorporated into the dash cluster.

SloopJohnB@mac.com

I've never had a CV joint dry out in 15 years of Audi ownership…I have had joint boots crack and throw lube but as long as that boot is patent the lube generally is. One exception was the inner joint on the A6….it was brown mousse at 160K miles and 13 years…the boot wasn't cracked but apparently some water got inside it, probably from high water/puddles. The joint itself was not damaged, just cleaned it out and relubed/rebooted it.

To be fair I don't live in a rustbelt or super hot state/area, just DC/MD/NOVA

stupid939

Regarding the non-starting issue, there IS a flashing yellow car/key light on the dash. I bought a new key from the membership, but never took the car to them to have it re-programmed, as they suggested. I used my vag-com cable to reprogram the fobs, but didn't know I had to go through the immobilizer key matching process. I'll do that soon, thanks twentysevenliters! That should solve that problem. I'm hoping this should be the correct process:
Ross-Tech: VAG-COM: Immobilizer 3 Key Matching

As for the shaking problem. I was suspecting the CV joint by talking with friends, but as I said, I'm not really a car guy. I also though the tires could be out-of-balance from sitting so long, but I rotated them and the problem didn't go away. I'll jack it up again and start investigating and report back. I searched around, but couldn't find any pictures/videos/processes for rear CV joint replacement. Do any of you have a handy link? If not I'll figure it out as I go!

stupid939

Uh oh, I didn't read the link that I posted. Turns out I have to either take the car to the dealer to have it programmed to accept my new keys or disable the immobilizer using instructions on nefmoto.com. The second one sounds a little more fun...

twentysevenlitres

Glad I could help.
That Ross Tech procedure is correct, but you'll need the PIN code for your dash to get access to the IMMO module to do the programming.
Try following this thread:
https://www.audiworld.com/forums/a8-...01-s8-2873134/

My A4 did exactly that about 12 months after I bought it. Massive sudden vibration - felt like the wheel was going to come off!
Left rear inner CV had dragged a dry lump into the joint after a heavy bump in the road.
I repacked both rear inners and never had the problem again.

Airbag

Something is definitely bent or damaged .
Initial post states has been shaking since rear end hit a post. The damage looked extensive from the pic.
i think i'd look a lot further than dried out cv joint . possibly order a new half shaft ?

indoor

I know what's bent: the rear lower control arm that the jack stand is put under