arbboyd

Hello all. I'm hoping someone can help out. Purchased an 04 A8 a couple of months ago. Everything seemed fine. About a week after I got it home I got a check engine light for P1128 and P1130 . I have not driven it much since then, maybe 50 miles and now I have a boatload of codes coming up.

16684 P0300 Random/Multiple Cylinder Misfire Detected
16685 P0301 Cyl.1 Misfire Detected
16686 P0302 Cyl.2 Misfire Detected
16688 P0304 Cyl.4 Misfire Detected
17536 P1128 Long Term Fuel Trim mult.,Bank1 System too Lean
17538 P1130 Long Term Fuel Trim mult.,Bank2 System too Lean
17544 P1136 Long Term Fuel Trim Add.Fuel,Bank1 System too Lean
17546 P1138 Long Term Fuel Trim Add.Fuel,Bank2 System too Lean
17983 P1575 Right Eng. Mount Solenoid Valve Short to B+
17981 P1573 Left Eng. Mount Solenoid Valve Open circuit
18010 P1602 Power Supply (B+) Terminal 30 Low Voltage

Not sure what my first step should be here, have never had that much come up at once before. I do not have a vagcom but I do have an xtool vag401 but am still figuring out how to use the thing. Any help or suggestions would be great.

Jack88

Okay, calm down. Sounds like a couple of bad motor mounts and I would guess a weak fuel pump. The lean codes and misfires are tied together most likely. For the motor mounts, look to see if there are signs of fluid having leaked out of them. I am not familiar with the P1602 code, though.

jlbell

First and easiest thing you can do is purchase a Ross Tech system to know the exact Audi Dynamic Trouble Codes (DTCs). However, using the codes you have, work your way down a least to most work diagnostic approach. First get as much documentation on the car as possible, if you plan on keeping and maintaining it yourself! Secondly, look at the codes and take a breath as Jack88 suggested, maybe even reach for a beer/two, or whatever brings you down. Terminal 30 Low Voltage, via my documentation on current flow (basic equipment for the D3) suggests it is either: Terminal 30 voltage supply relay, Screw connection for terminal 30 (battery), or Screw connection for terminal 30 (starter). So your best bet is to start with checking the battery, and battery lead connections in the trunk then load testing it. As a lot of these issues and DTCs can be caused by a weak battery. Secondly, and I can't stress this enough is to invest in a Ross Tech tool as you can see if the battery management has activated any of the Quiescent Current Stages X (1- ∼ 10). This basically tells you if the battery is dying (or has a draw), and if the battery management system (BMS) has activated certain systems to shut down and not start up until after a certain voltage is attained after start! Starting power is what the BMS is trying to preserve so it shuts every other no essential system off. If you don't see any issue with starting power, then move onto ignition coils and spark plugs. I know from experience that the ignition coils can fail out of the blue. As in my experience, I just finished a major repair of the hydraulic adjusters, which involve the removal of all camshafts, and upon start-up it was misfiring on all cylinders (I immediately thought the timing was off, via the camshafts), but it turned out to be a combination of failed ignition coils (they literally were working perfectly before the repair, but I guess two weeks on a workbench is a lot of stress), and missing vacuum hoses that caused the misfires. Back to the diagnostic lesson, move cylinder 1,2,4 ignition coil to 5,6,7 (or whichever cylinder) and see if the issue migrates, using your diagnostic system, If no migration occurs repeat the same process for the spark plugs. Lastly, if no DTCs migrate for either ignition coils or spark plugs, then, as Jack88 suggests, you have a fuel supply issue. The best place to start with this is to check the fuel pressure at the fuel rail if you're not receiving the specified fuel pressure than you need to work backwards starting with the fuel filter, and the fuel pumps. With regard to the engine mounts, I believe there is a similar post, currently active, containing the same error code, that may help you (in addition to what Jack88 has suggested).

dvs_dave

MP4.2+6.0

+1. For running issues, this would be my starting point. Codes are both Bank 1 and 2, which on a 4.2 means both sides of motor. Lean running can then also generate misfires and those codes. Look carefully at everything from the MAF sensor to the intake manifold proper. Could be as simple as a loose clamp on the joints from the MAF on the way to the throttle body bolted to the intake. The suck pump, vacuum pump--aka 10 other names for the Y fitting that ties in the power brake booster line--hooks up in there somewhere too and can get dislodged. Some like that are often loud enough to hear the air being sucked in. Others just need careful look. From BTDT, my first hunch might be the loose ginormous clamp stuff. Fuel possible too, but vacuum most common at margin and usually pretty easy to either find issue or move on to other common areas as highlighted in the various responses.

arbboyd

Thanks everyone. I'm going to start with the battery, It's showing 11.8 volts so maybe that will take care of some of the codes. Then I'm going to look at the maf and look for vacuum leaks. Am also going to purchase Ross Tech VCDS. Once it stops raining I'll tear into it and report back.Thanks again.

arbboyd

Just an update. Have found several vacuum leaks, a missing hose clamp on the maf section, a bad air filter and a dying battery so far. Have ordered the filter and battery. I do have a question about one vacuum leak. One was simple, just a cracked hose. The other was just missing. There was a vacuum fitting on the air box (pic one) and the only other missing fitting I could find was the one in pic two. I searched around and am thinking it must be something with the secondary air system. I just wanted to check before I put it all back together.

dvs_dave

arbboyd

That was the thing, could not find any loose hose. Pic two was the closest non-connected fitting I could locate. I'm 90% sure that's where it goes, just wanted to verify from someone more knowledgeable than myself.

arbboyd

After a new air filter, vac lines and cleaning the maf all issues seem to have been fixed. Simple enough.