Emission Control System Warning Light (A4 Avant 1.9TDi 130PS AVF Multitronic)

[trlaing]

Hey guys!

I'm new to this forum and hope someone might be able to help here....

I have an Audi A4 Avant 1.9TDi Multitronic with AVF engine. I have a K&N induction kit (57-0533-1) and a Tunit V-PD installed.

I have done at least 3000 miles with this setup with no problem until a couple of days ago - The Emission control system warning light came on the dash when driving my short journey home from work.

I removed the Tunit and the light went off, so I re-installed the Tunit and the light stayed off during my drive to work the next day. The light appeared again coming back from work. So, I removed the Tunit and drove to work this morning and the light came on again half way through my journey.

It may be worth noting that I have been using Millers Diesel Power Sport 4 diesel additive for the last few months.

Any ideas to what could be activating the warning light? I know it could be many things, from stuck valves to faulty sensors. At least if I can get some ideas before removing my upgrades and giving to the Audi garage for diagnostics.

[Dave Avant]

K&N air filters and MAF sensors don't go well together as the K&N filer is oiled to improve filtration.

I have a K&N panel filter, but before I installed it, I gave it a quick wash to remove the excess oil in the filter, made the water in the sink red!!

Basically the oil gets sucked onto the hot wire MAF sensor and eventually, usually after a few thousand miles the MAF starts to interpret the airflow incorrectly, due to the oil on the delicate wires.

try removing the MAF (black cylinder on the exit of the airbox with a plug ontop) and clean it with electrical spray (from maplins or electrical retailer) and blow dry with compressed air if you have a compressor - if not just let it drip and dry - DO NOT touch it, it is very delecate.

It could be a dodgy Tunit box - its not on a high setting is it?

[trlaing]

The Tunit is set at 6 and has been since 1 day after I installed it.

I got the fault diagnosed at a garage I know and it is a faulty coolant temperature sensor (G62).

I'll be booking it into Audi soon to replace it after removing Tunit and K&N - still under extended warranty

Thanks for your help!

[dub love]

yeah, i dont understand how people can sell these K+Ns when they must know that they mess up people's MAF [Mass Air Flow] sensor's its not cheap either, your looking at about £140 to replace. a chap last week came into Brimlowes with a 1.8turbo TT, said it runs like ****, pop the bonnet then mate, wats that! thats your problem, big K+N, he didnt believe me so i told him to go get his airbox, put that on for him and it was still running ****. phoned audi, MAF problems, needed to replace the whole thing. he was certain that the K+N wasnt the problem just because he had orderd it for that car, THEY WILL SELL YOU ANYTHING, BE WARNED,



[shuffle records]

if you put it back on after visiting audi you will have same probs all over again

[Dave Avant]

Usually a good clean with leccy contact cleaner will cure it, I would wash the excess oil off the filter. Mine has been on for 5,000 miles now.

But I did look for a non oiled filter first.

The earlier MAFs were worse, and some MAFs are worse than other, Pierburg seem to be the most reliable.

[trlaing]

Fault was the coolant sensor as expected. Now replaced and working fine again

Turns out nothing to do with the K&N or Tunit - handy! Will be refitting when rain stops

I've actually done 7000 miles in almost 9 months with both fitted with no problems.

Enjoy!

[ulters]

just bought a 55 plate a4 1.8t
high miles but in good nick, no timing belct changed yet.
drove it about 150miles and emissions light came on?
any ideas?
bringing it to my local garge to be serviced - not a dealer - at the weekend, so just wondering,
cheers,
ulters