Idle fluctuation

[Novica]

HI
As I am a new owner of Audi A4 Avant 2004 year (engine code AVF 1.9 tdi 96 kw, 141000 km) I noticed that my RPM is fluctuating from 861 to 882 after few moments when the engine is started and when is warm. But the RPM is jumping from 861 to 882 as shown on vag com and it is not showing any other number between, only these two. When I bought the car (1 month ago), he was due to change the timing belt, and I do it by myself. I was thinking that this and ALL new filters will cure the problem but nothing the engine is still fluctuating 20 RPM. I am wondering is this normal or something will go wrong soon? I attach also engine data meassured with vag com, I compared with elsa and vag com and they are in range. The data were taken before I change timing belt and filters, after that I did not write the data but they are almost the same except channel 004 that synchronisation angle is now 0 without fluctuation (because of new spanner and belt and sync. of engine) and injected quantity is increased slighty up to 6.5 mg/S as I remember.

[Crasher]

I can’t see anything out of the ordinary there apart from it does seem to be warming up faster than I normally see but then again I can’t see any time base info on the Measuring Block groups. Can you see this fluctuation on the dash rev counter and feel it through the car? Did you use locking tools to set the cam timing?

[a8 tech]

Exhaust gas reg cutting in,reduce the egr cycle or make sure the air con is off as well as other consumers and rev the engine and recheck the idle speed any load on the alternator will alter the idle speed so will the egr duty cycle so either adapt the egr out or block its vacuum and compare the results,unless you have set the valve timing incorrectly i would look at the egr side but a fluctuation of this low rpm is totally acceptable

[Novica]

I took all data when aircon and all electrical cons. were off and I use locking tools to set the engine, I am thinking to reduce the EGR but I am affraid if I can harm the engine with that, because I read somewhere that combustin temp will encrease due to huge amount of air?On rev counter I can not see the fluctuation but I can feel a weak vibration on car.

[a8 tech]

well its either fueling or the dual mass is starting its slow and expensive signs of failing

[Novica]

When I change the air filter I found lot's of garbage inside I was wondering how is posible that the MAF is still functioning!

[Crasher]

Because it is below the air cleaner. On more than one occasion I have found a mouse nest in an air box, must give the poor little blighters one hell of a shock under full acceleration.

[a8 tech]

Don't get to worried about debris in the air box and the air mass would give signs of reduced power but you can test the airmass at idle and 3000 rpm under load also disconnect the airmass and monitor your fluctuation.I would advis the inlet manifold to be removed and cleaned out as well as the egr valve as this wont hurt but improve the running because they get gunked up but if the overall running is ok then maybe your looking to deep.Regards A8

[Novica]

I will check it tomorow. The car is going fine and cold starting (until now the lowest temp at my place was round 0 C) is ok without smoke just that I did not get used on this fluctation because I had passat with similar engine and RPM was constant. I looked few days ago inside air intake and flap but only from rubber hose hole and it was clean, except on the cone of EGR valve a small deposit of dirty and was slighty oily inside.
Thanks for sugestions.

[Novica]

I did these experiments today, only thing that I noticed is that when I disconect a MAF the fluctation was still present but a longer time passed between jumping of RPM. Disconecting of EGR did not change anything. After that I took live data from engine (a/c, radio and all elec. eq. off, EGR and MAF conected) where You can see fluctation.
Remain dual mass, how can I check it?