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As far as vacuum leaks, I have never had any vacuum leaks related to any plastic lines on my 2005 A8L W12, which is now at 200K + miles, but on the other hand, I found many vacuum leaks on my Bentley GT during my rebuild, the Bentley has vacuum lines that run along the firewall behind the steering rack, along with plastic vacuum lines that run to the top of the transmission midway back for both turbo solenoid valves, I do not know at the moment if the Audi has the same vacuum lines at the firewall area, the Bentley firewall area lines feed vacuum to the rear of the vehicle for evap, and exhaust flaps operation, not sure if the A8 has the same routing at the firewall, but definitely nothing over the transmission.
But most importantly, I had the same issue with lean codes, and stutter, sometimes the engine would stumble and lack power after a restart after being shut down for about an hour, but if I kept on the pedal and brought it to 3900 - 4100 RPM iirc, it would kick-in full power like a kick in the ***, like hitting a switch, of course the engine light would flash when I did this, and it was odd, because, if I shut the engine down and restarted it, all was fine for a while during the drive, it made me think that it was something electrical, so, I went through all kinds of testing, even spraying starter fluid around the engine while running to look for leaks, rpm should raise if starter fluid found the leak, but no go, and being that you can't run the engine without the intake manifold in place, it was tough, I had put all new plugs, coils, intake manifold center gasket, 02 sensor, fuel filter, checked fuel pumps, still the problem remained, and it seemed dependent on the temperature of the engine, and sometimes the season, the only thing that I could not reach spraying the starter fluid, was the injectors, so I pulled the intake manifold and swapped out all the injectors and their o-rings with the larger injectors from one of my Bentley engine teardowns, well, problem solved, and a little more power... at least going by the seat of the pants feeling 😅, the o-rings on the injectors were very brittle and cracked.
At another time after letting the A8L sit for a little over a year, a little friend chewed up some injector wiring, so check that also.
.
These are the leaks that one would find on the Bentley W12 TT, But we don't have this setup on our A8L W12's.
Johnny
Last edited by Giovanni Giovino 6.0+6.0TT; 03-26-2022 at 07:46 AM.
Reason: SPELLING
As far as vacuum leaks, I have never had any vacuum leaks related to any plastic lines on my 2005 A8L W12, which is now at 200K + miles, but on the other hand, I found many vacuum leaks on my Bentley GT during my rebuild, the Bentley has vacuum lines that run along the firewall behind the steering rack, along with plastic vacuum lines that run to the top of the transmission midway back for both turbo solenoid valves, I do not know at the moment if the Audi has the same vacuum lines at the firewall area, the Bentley firewall area lines feed vacuum to the rear of the vehicle for evap, and exhaust flaps operation, not sure if the A8 has the same routing at the firewall, but definitely nothing over the transmission.
But most importantly, I had the same issue with lean codes, and stutter, sometimes the engine would stumble and lack power after a restart after being shut down for about an hour, but if I kept on the pedal and brought it to 3900 - 4100 RPM iirc, it would kick-in full power like a kick in the ***, like hitting a switch, of course the engine light would flash when I did this, and it was odd, because, if I shut the engine down and restarted it, all was fine for a while during the drive, it made me think that it was something electrical, so, I went through all kinds of testing, even spraying starter fluid around the engine while running to look for leaks, rpm should raise if starter fluid found the leak, but no go, and being that you can't run the engine without the intake manifold in place, it was tough, I had put all new plugs, coils, intake manifold center gasket, 02 sensor, fuel filter, checked fuel pumps, still the problem remained, and it seemed dependent on the temperature of the engine, and sometimes the season, the only thing that I could not reach spraying the starter fluid, was the injectors, so I pulled the intake manifold and swapped out all the injectors and their o-rings with the larger injectors from one of my Bentley engine teardowns, well, problem solved, and a little more power... at least going by the seat of the pants feeling 😅, the o-rings on the injectors were very brittle and cracked.
At another time after letting the A8L sit for a little over a year, a little friend chewed up some injector wiring, so check that also.
.
These are the leaks that one would find on the Bentley W12 TT, But we don't have this setup on our A8L W12's.
Johnny
dang that’s insane! Johnny
I think I’m going to go after those injectors sparks or coils
now.
The car is still the same . I haven’t gotten any codes for lean( although I have to drive it more) but it’s still hesitating when increasing throttle. It starts perfect idles smooth, even drives ok under light load( less than 30%)
I changed the drivers side fuel pump/both relays to see if it was transfer pump But no change .
When I got misfires under load both times I got random misfire on cylinder 4 or 11 or both. So that’s why I think maybe injector .
those injectors are quite pricey , cheapest I found was $70 for 1, any tips where to save alittle. maybe I can buy only a few injectors , swap 4 and 11 see if anything changes???
Update* turned out to the failing coils causing the hesitation under load. No fuel problems
Glad to hear that! I must admit I'm a little jealous; Oyster Gray is a spectacular color! And a W12 for that price?! Wow. I mean, I understand why the used car $tealers won't deal with it - not enough money to be made - but looking at it from our angle, you have one of the best luxury cars of all time for the price of an expensive dinner out! (Okay, a very expensive dinner, with wine )
Glad to hear that! I must admit I'm a little jealous; Oyster Gray is a spectacular color! And a W12 for that price?! Wow. I mean, I understand why the used car $tealers won't deal with it - not enough money to be made - but looking at it from our angle, you have one of the best luxury cars of all time for the price of an expensive dinner out! (Okay, a very expensive dinner, with wine )
Now get 'er waxed and post some pics!
Haha yep with the s8 parked I get to drive this around . I’m loving the w12 buttery smoothness and torque all day!
I’ve done a few things that I haven’t updated yet.
I got the right fog light grill , rear lower bench , arms rests, beauty mirrors all replaced.
all in all I’ve replaced all sparks , a few coils to solve issue( the rest in order ), front right strut( that I had lying around) 2 beauty mirrors, lower rear bench, fuel filter, repaired a PCV hose, replaced right fog light grill.
I haven’t dumped that much but still need some brake pads after driving it, little things.
I became a master at taking off the entire intake manifold after removing/installing 4 times.
i think I can get it off like under 10 mins maybe 5 now lol
here’s a few pics:
I put the 20”sport summer wheels on, with the 15 mm spacer in front and 20mm in rear.
Last edited by Christian A; 06-14-2022 at 10:21 AM.
03-26-2022, 07:31 AM
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