N18 solenoid voltage egr control question?

[Q plate]

Hi I'm new to the forum, I would appreciate some advice if possible on this as I don't have V cats just a cheap scanner. I bought an 04 1.9tdi 112k estate last summer to replace my older but trouble free A6. I drove the car 180 miles home and all good. Ive not used the car since due to working away and a couple of rust scabs have now turned into prepping for a full respray. The car starts fine and is normal whilst cold but once it gets towards temperature it has no power, doesn't want to rev + smokes. If I disconnect the EGR vacumn hose its o.k. Ive ran a test and it gave me a code of 19586? from memory egr related. Ive cleaned the EGR which wasn't excessively caked up, cleaned the maff checked and replaced the vacumn hoses. From what I've read the N18 controls the EGR by vacumn governed by the E.C.U but I've got a continuous 12/14 volts present hot or cold so I don't understand the mechanics of how the egr is controlled to partially open? Whilst I have the bumper off I replaced the clutch pulley on the alternator and to improve access dropped the front panel forwards a bit, Ive since removed it again in case I'd trapped any wires but all looks good. Only other thing is the airbox wasn't correctly sealed on inspection as 2 of the clips were missing which ive replaced. Ive also checked all the hoses I can see but can't see any damage or splits. I'm happy to blank the vacumn pipe and leave the EGR closed but id like to get to the bottom of the problem in case its something more serious.

Thanks in advance

AL








Thanks

[bluezie]

The EGR (and N75 turbo) valves are controled by pulse width modulation. A square wave form signal oscilating from 0V to 12V is fed to the solenoid, and the width of the 12V portion of the waveform determines how much the solenoid opens (duty cycle), and hence vacuum level. Digital multimeters tend not to like any waveforms that are not pure sine wave. An old analogue meter will give and RMS voltage, and will be more of an accurate reflection of duty cycle.
Sounds to me like the EGR is stuck open, maybe the N18 is faulty? and the engine is overfuelling for the air available, or you have a boost leak.
VCDS or similar diagnostics is the way forward, as it's a big window into what's happening here.

[Q plate]

Thanks for the info I understand what your saying now about the meter, I've got a few more things to check including the pipes again before looking at getting it read properly. I did notice last night I can hear a buzzing kind of noise coming from the turbo actuator so I'll check that next in case the diaphragms fupped.

[Q plate]

Fixed bought a copy of vcds as suggested & did the output tests, nothing from the solenoid. Replaced with a cheap used n18 and all good. Looks like it was passing a small amount of vacumn all the time. Going to read up on setting the egr values lower now & setting the windows to open off the remote which I had on the old car and was useful in the summer. Cheers