B4 TDi "Check Engine" Light on

[NiGh7]

Hello,
after 300k km (about 190k miles) the check engine light came on for the first time today. The think is though, what does the lamp itself mean, after a brief search I found nothing, even in the car's manual.
Worst part of all is the loss of power, the engine revs, but its kinda slow (or slower than usual) when accelerating, its sluggish. Anyone with ideas is most welcome to share them.

[shaun5]

Total guess but have you got a split boost pipe? does it smoke on acceleration? Does the light go out when you restart? or is it on permanently?

[NiGh7]

No split boost pipes, it usually smokes on accel., now it doesnt, the light itself is constantly on (no flashing), when I restart it comes on after around 30s.

P.S The car also judders/shakes on idle when the engine is hot, its not present when cold.

[Lago Blue]

NiGh7,

Hi sir,

First off I am not the right guy to answer this not having a diesel, but to get you started, here goes. Perhaps someone who knows better than I will jump in.

To your first question, the light is saying you've had 300k km to get the factory manual if you really want to learn how to do this yourself; and if you do learn it is money well spent, so get out the book. Not really but that is true. It (the lamp a.k.a. CEL (Check Engine Light) or MIL (Malfunction Indicator Light) is saying the car itself senses sub-optimum running conditions, has saved info about that and can tell you more if you pull / extract the codes from the ECU. Whether they are called blink codes or DTCs (Diagnostic Trouble Codes), you might best get them to begin to get to root cause of your CEL.

In North America excellent paper manuals are available, in Europe and for your diesel, I have no idea.

To be honest, if your query about the interior light switching logic is not within your current grasp, this engine issue may be beyond it till you gather more info. However if you are determined to learn this, get the applicable factory repair manual for your exact car and engine (or in touch with someone who does) which is going to list diesel diagnostic codes (perhaps there are some TDI specific ones?).

If need be, you can make good use of the manual to also orient you about the various engine bay components and the required maintenance procedures.

With the model year of your car you are going to have to determine the Audi (2?) letter designation for your particular engine, whether it is OBD I or II, where to connect to, to pull codes and what method &/or equipment is required to pull and read the codes. It will help to identify the connection's location, type and quantity. If you have to, get the codes read for you.

Often the issue is emission controls related, and in turn often has drive-ability and / or fuel economy effects. Getting the code(s) from the car -may- put you onto what system needs attention, for example the EGR system.

Consider that there is also likely help available on VW/Audi TDI specific forums that may be worth exploring.

Where to hook-up:
http://www.ross-tech.com/vag-com/cars/dlc.html

What is OBD:
https://en.wikipedia.org/wiki/On-board_diagnostics

[piotr]

EGR valve-check it.

[NiGh7]

NiGh7,

Thats irrelevant to the subject, If I didn't know what is what, I wouldn't even consider/bother to ask for directions. Besides, the interior lighting is a concern, because it lights up when I turn off the engine, but it doesnt from the switch, so its logical that there is another problem rather than a severed cable connection.

EGR valve-check it.

The diagnostics showed MAF (It's a '92 1Z engine) so its mechanical rather than electrical and the needle lift sensor on one of the fuel injectors, which when measured, showed 0 ohms of resistance. After unplugging the MAF, the car is even slower in terms of accel., but there is no difference at all when the sensor from the fuel injector is unplugged. Will try with a new one, but I have no idea about the judder/shaking of the car when the engine is hot.

[Lago Blue]

Re interior light, it may be worth checking that the ignition switch (they're known to fail frequently and can cause a variety of issues, how recent is yours?) is not worn internally (it may be just starting to fail, they all do), common with simply old or particularly non-OEM switches or if it might have been loaded by the weight of several keys over time. As a check, you can plug in a new one quickly without fully installing it to see if your issue improves. In any case then you'll have a known good new OEM switch, not a bad thing. Some folks apparently fit the equivalent Porsche switch for exactly the above reasons.

[JuizeR]

Check engine light is most likely due to the needle lift sensor, I think you need to renew the whole injector on cyl.3
MAF might be acting up because the faulty lift sensor. I'd chance the lift sensor first and then have a look at MAF after that if it still acts up.

I had one of these back in the day and I miss mine.
I remember mine had some strange issues when the light switch inside the glove compartment broke, if I remember correct it was connected to instrument cluster and other lights somehow.

[NiGh7]

Well, diagnose said "00542" Needle lift Sensor (G80) 05-00 Input Open, connected a 100ohm resistor to It - still doesn't work. Any idea how can I fix it without changing the whole injector?
Also the sensor itself is kinda "molded" to the injector so its unchangeable.