Wrenchman

Hey folks, Brand new to the forum and also new to being an Audi owner.

I bought a 2001 A6 2.8L Quattro as my commuter car a month ago. It had the engine light on before I bought it; I took it down to the local mechanics and had a light diag (non-VAG) ran on the car. (1st mistake.) It spit back Evap codes, cylinder 2 misfire, O2 sensor, cat.

I bargained the seller down $800 thinking it's about what it would cost to fix the issues. Drove it around for a while and notice a shimmy or hiccup because one of the cylinder misfiring.

Brought the car home and noticed oil in all the spark plug cylinder sockets after removing the old ones. Bought a valve cover gasket and spark plug seals and threw new ones in. I replaced the bank 1 sensor 1 02 sensor, new plugs and air filter and fired her up.

Car is now misfiring on 4+ cylinders.

I replace the coil pack and all spark plug coil wires and regapped the plugs. Car is still misfiring. Badly. Power is down 90% -- I think the computer put the car in limp mode and it's running on maybe two cylinders.

Got sick of throwing parts at it. Took it to firestone and had a VAG run. Master mechanic (who kind of seemed like a hack who was busy taking the money from schlups with much more minor issues) tells me he took out an O2 sensor and test drove it -- it ran much better. Tells me it's the catalytic converters. Great. Didn't tell me which cat or which 02 sensor or if it stopped misfiring entirely. Tells me to take it to the dealership for a triple cat replacement with OEM and a ECU wipe to take it out of limp node. No thanks. It would cost more than what I bought the car for.

So here's the deal. I've ran a compression test on the engine. 120 PSI on all 6 cylinders dry. I ran a back-pressure test on the passenger side and it came back clean. I'm thinking the culprit is the Catalytic converters upstream, since I find it hard to believe the downstream would be causing misfires and it's not throwing code.

The two upstream Cats seem IMPOSSIBLE to get to. I've removed the coolant hoses and tank on the drivers side and the air system on the passenger side. I've been able to remove ONE of three nuts. In another thread a contributor said to go through the wheel well after wheel removal -- there's a fat sheet of metal and a heat shield that prevents me from going that route -- had a mechanic tell me to take a 3/8ths socket with extension and impact swivel and go from the bottom. There's a $hit loan of metal and component between the cat and the bottom. Also not a choice. I've attached some pictures for whoever can help. It also seems like the backside or tail of the cat is welded and not bolted on. I'm hoping someone who has done this before can provide specific, realistic help for me.

Thanks for reading and Prost!

Wrenchman

For those with legal concerns to what I'm doing -- I live in a county in Colorado that doesn't have emissions testing regulations. The political thoughts behind that were "since the internal combustion engine has a obsolescence of maybe another 25 years, the ozone and atmospheres will have repaired themselves with decreased emissions long after this issue impacted our planet." Makes me a lucky guy.

All I'm trying to do is get the cats out, bang out the porcelain and platinum inside, dump em out and put them back it. Worse-case scenario, I'll buy some OEM's myself and throw them in there.

Thanks for whatever help the forum mechanics can provide.

Warmly,

Cory

Wrenchman

Update: Pulled the O2 sensor out of the Cat pictured below. It's about as fried as I've ever seen.

My first thought was to go buy a new 02 from AZ and throw it in there and hope for the best; then reason prevailed. The O2 is fried because of cloggage in the CAT.

Wish me luck.

Wrenchman

Progress update: After removing the skid plate from the bottom and jacking her up on all fours I found the CAT bolts much easier to access from the bottom. This is a close up from the bottom probably about a 14-16 inches from the cat connection to the manifold. Don't mind the fluid, it's coolant from a plastic tee connector for the coolant junction I busted while moving the hoses out of the way. Replaced it with brass so it wouldn't happen again.

So with a double extension and a 3/8ths socket(like the mechanic said) the bolts can come.

Next problem: there is no exit area for this [bulky equivalent of an appendix for an exhaust] thing to exit it's position, from either the top or bottom. Totally baffled as to how people remove this on this model car without majorly dismantling it and putting it up for 2 weeks.

Wrenchman

Like hell. 40 minutes of war and they're starting to look like they want to strip. Not recommended if you don't have battery powered or air compression impact.

lucio_liu

I don't believe a new CAT will solve the misfire. pre-cat O2 sensor could affect MPG a little (maybe 2-3), but yours O2 sensor are not worst I've ever seen.