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I had a steering knuckle in my shed. Really!
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Discussion Starter · #1 ·
It's a B5 A4 with the AEB motor. My son bought this car from me a few months ago.

The idle is high when the motor is warmed up (the P0507 code). The other codes say vac leak and insufficient vac for the EVAP system.

I thought they would be related with a vac leak going to the EVAP, but a fairly cursory look didn't reveal any vac leaks over that way.

The EVAP hose going to the TIP is chafed from the heat shield on the air box, but it doesn't appear to be all the way through the hose.

Any thoughts? It's pretty damn cold outside here now, so knowing ahead where to look helps keep me warm.
 

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P1136 Fuel Trim: Bank 1 (Add): System too Lean
Possible Solutions
Check Mass Air Flow (MAF) Sensor
Check Fuel Pressure Regulator
Check Fuel Pump
Check Intake/Exhaust System for Leaks
Check Secondary Air Injection for Leaks
Check Vacuum Lines for Leaks
Special Notes
Fuel Trim Info
When this fault is stored and external vacuum leaks are not found, less obvious problems may be present:
Check Evaporative Emission (EVAP) Canister Purge Regulator Valve (N80)
Check Brake Booster and Hoses
Check Electric Vacuum Pump ( If Applicable )
Check Crankcase Ventilation System for faulty components. When the PCV or Crankcase Ventilation System is faulty, vacuum is typically present under the oil cap and misfire faults are common.


P1476 EVAP Leak Detection Pump: Malfunction / Insufficient Vacuum
Possible Symptoms
Malfunction Indicator Light (MIL) ON
Possible Causes
Evaporative Emission (EVAP) System faulty/leaking
Evaporative Emission (EVAP) Leak Detection Pump faulty
Insufficient vacuum supply to the Leak Detection Pump
Possible Solutions
Check Evaporative Emission (EVAP) System for Leaks
Check Evaporative Emission (EVAP) Leak Detection Pump
Check vacuum supply at Leak Detection Pump


P0507 Idle Control System RPM: Higher than Expected.
Possible Symptoms
Malfunction Indicator Lamp (MIL) active
Possible Causes
Throttle Valve Control Module (J338) dirty/faulty
Wiring/Connector(s) from/to Throttle Valve Control Module (J338)
Vacuum Leak
Possible Solutions
Check Throttle Valve Control Module (J338)
Check Wiring/Connector(s) from/to Throttle Valve Control Module (J338)
Check Intake System for Leaks
 

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Perhaps take a look at the throttle angle when (fast) idling, and the MAF g/S reading. Maybe there is a leak somewhere such that the motorized throttle can't close enough, to maintain a correct idle speed. My A4 had a hard-to-track-down problem with the EVAP pump- turned out to be a broken hard vacuum line behind the left-rear wheel well liner. Evidently rocks will sometimes be thrown hard enough to crack these lines, and the resulting leak is hard to find.
 

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First, pinch or block the line from the N80 to engine side to see if that changes a possible vac leak condition. That will rule out a faulty valve. Beyond that, you are looking for broken plastic evap lines, most likely at the rear. My 99 had cracked evap lines where it ran under/around the spare tire well.
 

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I had a steering knuckle in my shed. Really!
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4,159 Posts
Discussion Starter · #5 · (Edited)
Ok guys thanks for the input. My son did say he smelled a little gas near a rear tire once, so that's a starting point.

Anyone think that the Evap leak is also the vac leak giving him the high idle and too lean code, or does he more likely have separate problems?

Edit: I just realized pinching off the hose from the N80 to the intake (VAGguy's suggestion) will let me know if the Evap leak is also the vac leak.
 

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The easiest way to rule out an EVAP pump leak is to disconnect the hose at the check valve, and plug the valve. If the idle slows down, and the lean code doesn't come back, then there must be a large leak somewhere along that line. The vacuum hose for the EVAP pump comes from near the ABS pump and the check valve is somewhat under/behind the throttle housing.
 
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