Rich idle,unburnt fuel

[A80Avant]

what can cause this problem that appeared on me today?
I recently replaced a MAF that had bad idle problems with a previous one that worked fine except the high rev range(measured on the remap while in germany and it was suggested to me to replace it).

What should i check? VAG COM turned out only fault code 561 intermittent telling me to look out for fuel regulation and possible G70 check(MAF).

Fuel problems could only be of bad fuel filter,although it is a year old but i have my doubts,since the fuel pump is sounding a bit louder than what it did back in Germany.

MAF again???

What could cause so frequent MAF problems except being a bad sensor itself?The thread is there,hasnt been sucked out in any of the mafs i have tried on,but still i cannot understand it!

Can this also be an O2 sensor fault?

thanks
Vasilis

[A80Avant]

bump

today i tested an older maf whici was replaced due to being faulty but i thought it give it a go,did the same thing.

on idle,it works fine with lamda 1 for 10-15 seconds,then starts to caugh and lamda goes to 1.20,black smoke and fuel smell from the rear.No fault codes on vagcom though

[GazzaG60]

sounds like an o2 fault. do you have a AF gauge.

when i had a dead probe i saw middle which is around 14:1 for the warm-up time of the probe, then it went to 1 bar which is lean. the ECU adds more and more fuel bit by bit as it detects a lean state from probe. which in turn causes chugging and smoke.

i had this a couple of times due to bad wiring as much as the probe. on the corrado that is.. one time id lost 1 of the heat wires and the other time it was a ground issue. grounds are are the most important part of the 02 setup.

[A80Avant]

i havent tested the O2 yet.I dont have the AF gauge.Only what i see with vagcom.

i found a replaced the maf again with a S4 maf i had to see if it makes any difference.tomorrow i will try to replace the O2 as well.I do have one not an audi part but i guess it will do the job

[A80Avant]

found that one of the 2 earth screws on the intake was loose...if that means anything...

[A80Avant]

O2 replaced,same effects.no cure.

[UrS4boy]

O2 replaced,same effects.no cure.

Could be MFTS (3B) or G62 temp sensor (AAN, ABY, ADU):

http://forums.audiworld.com/s4s6/msgs/148742.phtml

Otherwise, intake tract rubber boot leak after MAF.

[A80Avant]

this sensor is also new.i replaced it just after i left for the summer holidays.

a boost leak after the maf,you mean the large hose that goes to the turbo?That is now replaced with metal tubing and the little parts that remain as hoses are samco and are checked for leaks.havent found anything...

[A80Avant]

well...
it seems that the screws that were unscrewed,got me screwed as well...
I tightented the earth screws(both were loose) on the IM and what do you know?the car doesnt have any black smoke anymore!!It seems to be running much better

Went for a drive,ok my old S2 MAF is out,i knew that,so i plug the one i had on the europe trip.....Evrything back to normal.

However i do get the O2 sensor fault on vagcom,and the 561 ...add exheeded.

I replace the aftermarket O2 sensor i had used to the previous one so the O2 sensor fault also cured.Now only the 561 fault to battle with.

I will change the fuel filter soon as i havent done that yet,and i will also use the new maf,since the fault code described this one as either fuel pressure low,or G70 check.(also exhaust leak prior to catalysts but there is none on my car).

hoping to get an answer soon..

but look out for those loose screws....i was this close on building up boost agains a wall!!!

[newsh]

Here's my recent experience

http://www.s2forum.com/forum/showthread.php?t=24544

[A80Avant]

i did read your post newsh.it is very interesting.The difference is that my unpluggment of the plug had reverse effects,which indicated that the maf must be indeed damaged.I checked the plug and it seems ok for now.In general though i believe the maf should be further away from the turbo especially if it is a big one.turbulance can scram with the signal so my next step would be to cook something up to put the maf in a colder and better place.