After the first longer (350 mls) trip after installing the new/used transmission, I pulled the codes below:

P1504: Intake leak: where do they typically occur? Obviously, the flex duct between MAF and engine with its 2 hose clamps. Else? Would spraying starter fluid (or carb cleaner) work to locate?

P0401: EGR flow: check vac lines to EGR. Hook up hand vac to valve to check if it moves and maintains vac? Ditto run engine, apply vac with hand pump and check if idle worsens?

P0156: O2 after cat. But which side? Swap around to see if error moves to to other side?



VCDS Version: Release 10.6.3
Data version: 20101206

Thursday,20,January,2011,11:18:41:22662

Chassis Type: 8D - Audi A4 B5
Scan: 01 02 03 08 15 16 17 25 35 37 45 55 56 57 67 75 76 77

Mileage: 212240km/131879miles
-------------------------------------------------------------------------------
Address 01: Engine Labels: None
Part No: 8D0 906 266 B
Component: 2,8l V6/2V MPI OBD2 D01
Coding: 01251
Shop #: WSC 06325
VCID: 2B5BF371F383

3 Faults Found:
17912 - Intake Air System: Leak Detected
P1504 - 92-00 - Unknown Error Elaboration
16785 - EGR System: Insufficient Flow
P0401 - 93-00 - Unknown Error Elaboration
16540 - Oxygen (Lambda) Sensor B2 S2: Malfunction in Circuit
P0156 - 95-00 - Unknown Error Elaboration
Readiness: N/A

 

First code: inspect the intake tube and any/all vacuum lines related. Check also the small plastic pipe attached to the front of the airbox and running down to the SAP.

Second code: remove throttle body pipe (where the accordion hose to the MAF attaches) and clean out the throttle body - the EGR breathes into that area and can get blocked up with combustion byproducts

third code: B2S2 is the driver side post-cat O2 sensor (bank one is passenger side, sensor 1 would be the primary or pre-cat sensor). You can easily see it in the top of the exhaust pipe under the car. It may have damaged wiring from road debris or could just have decided to die. It doesn't sound like the type of code that could indicate a cat failure

 

Thanks for the tips.

"Check also the small plastic pipe attached to the front of the airbox and running down to the SAP."

What is the SAP?

I will check the intake and EGR items today. Does spraying as described by me help to locate any leaks?

I will get to the O2 sensor next time I can get the car on my friends hoist. I suspect the wire got ripped (when installing the trans, I omitted to secure the wires to the 2 O2 sensors that run on top of the trans properly; good chance that they moved down and rub against the drive shaft).

 

SAP= secondary air pump it's part of the emissions system it only runs for a min on cold start, it's a 300$ pita. I'm not sure how that will locate leaks never herd of that one before.

 

Spraying carb cleaner (or starter spray) in areas with suspected vacuum leaks draws the cleaner in which upsets the idle. Very useful method to identify and proximity locate/find leaks in vac lines, particular in areas that are hard to reach.

 

Ok makes sense

 

 

The best I found with my forum searches was this write up. Are newer/better ones out there? Photos, particularly of the TB, the blocked passage, etc?

1) Remove the plastic battery cover. Using the 7/8 flarenut wrench, squeeze your arm past the ABS unit, and loosen the flarenut connecting the end of the EGR tube to the rear of the drivers side exhaust manifold. Remove the battery if you need more reach-in room. This is the hardest part of the whole operation.

2) Remove the plastic engine cover, remove the MAF to throttle body duct black rubber duct tube (loosen the two hose clamps).

3) Remove the black plastic throttle body duct: One hose clamp for the breather tube (drivers side), one squeeze-to-remove breather tube to the passenger side valve cover, and one vacuum line on the rear. Remove the two 10MM (11?) bolts on top, and then pull the duct off, by pushing it straight back towards the firewall. Careful not to lose the rubber bushings on the two guide pins!

4) Disconnect the cruise vacuum servo (one bolt, one hose, and a twisty (?) pin/wire at the linkage ball joint)

5) Remove the rearmost drivers side spark plug wire, and unplug the rearmost fuel injector (depress the wire spring, and pull straight off) for maximum access. Also, similarly unplug the square and rectangular plugs just rearward, mounted to a metal bracket, facing straight up.

6) Remove the two 10mm (11?) bolts which hold the EGR valve to the intake manifold. Use a 1/4 inch drive ratchet and short extension for the front bolt, and a universal swivel for the rear.

7) Pull the EGR valve off the intake manifold, and wiggle back and forth until the pipe to exhaust manifold comes loose. Now just set the EGR valve to the side, to gain access to the passage hole on the intake manifold.

8) Remove the blue vacuum line, and the two TORX head screws which hold the intake manifold changeover vacuum servo to the manifold. I did not pop the linkage ball off, just let it the servo hang.

9) Remove the 4 hex socket head bolts ("Allen key") which hold the throttle body to the intake manifold. If you want to remove the throttle body (for cleaning), disconnect the throttle position sensor plug, throttle cable (two clips), vacuum hose on the right side, and evap hose on the left side (clamp). Otherwise, you could just let the throttle body hang against the firewall. (Amazing how small the "Primary" throttle butterfly is!!)

10) The plugged EGR passage is now visible (!?). It is located on the intake manifold "floor" just behind the location of the smaller primary throttle butterfly was located. It is probably just a darker black circle, about the diameter of a pencil eraser.

11) Clean it out with a sharp instrument. Use a shop vac to try to suck up the carbon debris. Then clean the rest of the passage, which makes a 90-degree turn, and runs to the now exposed EGR valve hole. I used a foot long piece of aircraft/bicycle cable, attached to my cordless drill, as sort of a power-cleaning snake.

12) Reverse everything, and put it back together. Double check that you have not forgotten to reconnect any hoses, connectors, spark plug wires, vacuum lines...
Reset the computer by leaving the battery disconnected for 15 minutes. I did not use any gasket sealing compounds.

13) Enjoy code free, ping free motoring for another 80K miles!

 

1996 A4 2.8 2V auto, 136k miles:

I plan to take the EGR off to clean the mentioned passage (as the likely cause for the EGR insufficient flow code.

While at it, I plan to
- replace the brittle vac lines (3.5mm lines on order)
- take the throttle body off for cleaning

Should I
- take the upper intake off for cleaning? In this context: how about Seafoaming the intake?
- change the injector O-rings (I have heard at least one injector 'hissing'; stops when turning/pushing in just the right spot). What sizes do I need? Sources?
- I have a slight 'burnt oil' smell (particularly when parking the car in the garage after a longer drive); no drastic engine oil consumption observed (yet?), some 'wetness' at bottom of transmission pan observed, but no dripping/oil stains on ground.
- for reason above: check valve cover plastic breather tubes

I hear a 'diesel' sound from the engine (not valve clatter), particularly when cold and under load (sound smooth when warm and revving in neutral). Could that be caused by the EGR problem? Pre-ignition/pinging? I just filled up with 93 gas and added octane booster (to find out if that makes a difference).

Or should I look for an exhaust leak in the lower engine area, headers? I installed new gaskets for the flanges on the down pipes last time the exhaust was off.

I have new spark plugs in (Bosch Platinum with the quad things) in. At one point, I observe sparking between middle driver side spark plug shield and the block. Greased and re-seated the plug, seems to be gone now. I have a set of Autozone spark plug wires standing by. Should I put them on?

 

hey vtraudt, i was working on cleaning my TB and replacing vac lines, when i took off my "throttle body duct(green) i found the vac line(red) you mentioned in step 3) above to just be hanging unconnected to anything, do you know where this is supposed to go, i don't see any open connections.