icks90

Hi all,
loving your forum and the great tips you have on here! I'm already building a list ofjobs from your tech articles - slow wiper fix and leaking rocker gasket.

This is my first post askingfor help so please be gentle with me
After rebuilding and owning various landrover defenders for the past 12 years, I finally succumbed to owning something comfortable and fast – ending up with an audi 2002 a6 allroad 2.7t 6sp manual with 170k on the clock with full audi main dealer history.
By heck, its a quick car! Leaps forward like a scalded cat!!!

Anyway I’ve been enjoying it for a few months and its now developed a slight problem. Someone seems to have put Kangaroo juice into the engine. Idle is slightly rough, maybe varying by 50-80rpm up and down. Also when cruising with very light throttle it kangaroos, feels like it hesitates for a ¼ second then picks up, then hesitates, picks up etc etc etc. We’re not taking neck braking jolts, but you can feel it. Simillar thing happens on over run, you would expect the engine braking to be smooth, but it sort of feels like is ‘varies’ every half a second or so. As soon as you use any real throttle – maybe 10% or above – its absolutely fine. Full throttle is still hilariously fun! The really bazaar thing is that the amount it kangaroos can change from journey to journey, sometimes completely absent, other times quite bad.
First thing I did was unplug the MAF sensor. No change. Bum.

So I bought a cheap vagcom cable and installed vcds-lite and read the codes.
17861 - Exhaust Gas Temp Sensor 1 (G235): Open or Short to Plus
P1453 - 35-00 - -
17865 - Shareware Version. To Decode all DTCs
P1457 - 35-00 - Please Register/Activate

So looks like both my egt sensors have gone capput. Would these cause the hesitation effect at low throttle that I described above – or am I looking at something more than that? If it is just the EGTs, I aint spending £350 on a replacement, I’ll get them coded out with a stage 1 map instead

Any help would be greatly appreciated on what I should be checking to get this beast running back on song again.
Kind regards
nick

icks90

Oh, forgot to mention I get no CEL lights either.

massboykie

Hi Icks

The bucking (kangarooing lol) is probably caused by your EGTs seeing that you at least have codes complainig about them. I did not have any codes, but when I did the test sequence they "failed". Here is a link (http://www.vaglinks.com/Docs/Audi/C5...GT_Testing.pdf ) to the procedure... you need a loooong stretch of road... (3rd gear WOT if memory serves)

I would also suggest doing a boost leak check if you have not, seeing that it is a "new" car.

Hope that helps.

Cheers
Massboykie

icks90

Very quick update after some more miles of testing, this issue only seems to occur when 'off boost', ie literally tickling the throttle at say 35mph in 4th. Mainly between 1500-2500rpm.
Also I have a whine / turbine noise from the front of the engine when I turn the ignition on and the car sounds kinda 'farty' for the first minute when cold, like a blowing exhaust, but this literally stops dead after a minute and then sounds great again. Is this the SAI, as I thought that was only fitted to thee auto? Could these be related, or am I still looking at the egtsensors causing the rough idle and slight bucking at light throttle?

Cheers
Nick

massboykie

Hey Nick

As far as I know the manual gearboxes did not come with SAI.

Mine had a similar "power drop" issue at low speeds (low throttle) and although my EGTs were replaced under warrantee it still happened every now and then. Later on (few years) I did have my crank position sensor giving me stawling trouble (would just die at a traffic light and not want to start for a few minutes) and once I replaced the sensor the "drops" never happened again. ...but I have no real proof that the sensor was the longterm issue... to be honest.

I would suggest checking the misfire counts and seeing if the bad idling is caused by misfores on a specific cylinder(s)? Maybe the idling and kangaroo-ing is two seperate issues? Misfires are "common" on these motors, so if you can identify the misfires are from one bank or cylinder you could be looking at an ICM (ignition control module - on your airbox), ignition cool or maybe just new plugs.

Hope this helps...

Cheers
MassBoykie

icks90

cheers Massboykie,
will have to investigate how to look for misfires using my ebay vagcom cable and vcds-lite, as its supposed to have monitoring facility i believe built in... Although i would have thought misfires would have produced an error code, or does that only happen if it does it a certain number of times or due to a proper hardware failure?
bloody complicated heap this thing compared to my trusty old landrover!!! That thing could be fixed with gaffer tape and a hammer.

Nick

SloopJohnB@mac.com

AFAIK yes a certain number of misfires to set a code and/or a CEL or flashing CEL. However, you should be able to get a count of misfires even if you don't get a code set IIRC.

icks90

quick update on this problem and the mystery deepens.

vcds-lite is showing occassional random missfires on all 6 cylinders apparantly completely at random. say one missfire every 30 sec or so. certanly not in line with the rough idle or the hesitation / bucking you get in 'off boost' running.
put any boost on and the engine runs perfectly!!!

cleaned the maf, no difference.
unplugged the maf, no difference.

removed most of the intake pipework up to and including the turbos and refit it all with new hose clips etc and checked for splits - none.
the breathe system that goes into the top of the y pipe and inlet manifold and seems to go in to the air pump thingy (that whines like mad) are all sound and there are no hissing / sucking noises from anywhere else. Spraying brake cleaner everywhere at idle produces nothing in the way of changing revs or stumbling. so thinking maybe not a vac leak.

then the other day just as i turned the ignition on, the wife shouted me and i walked back to the front door. I culd hear thethrottle body clicking and whirring away for about 30 seconds and when i drove to work it was PERFECT.
every time i turn the engine on without waiting for the clicking and whirring to finish, it drives pants. Leave it until it stops clicking before starting the engine and it drives almost perfect.

what the hell?
Any ideas guys?

georgeb944

Vacuum leak.

I just found and fixed a similar leak on my 2001 A6 2.7T. It turned out to be that one of the bolts attaching the throttle body to the intake manifold was loose. Tightening that bolt and performing a throttle body adaptation (using VCDS), solve a long standing problem.

Incidentally, with the problem, idle was perfectly smooth and full boost was perfectly smooth. Only would stumble under part throttle. No other symptoms.

I built a pressure tester, and will try to duplicate the leak (by loosening the bolt) to see if it will show up using the pressure tester (and soapy water spray).

icks90

oh for gods sake, i'm starting to hate this car.
on the drive in this morning, the idle revs started to bounce from 400 to 1200rpm and it drove like death, with the abs and warning symbol appearing and dissapearing like mad.
from memory of reading stuff on here, thats a maf problem.
so pulls over and unplugs the maf, drives fine again!

so now totally cnfused.
obviously i am having a maf issue - but would a maf 'on its way out' also have caused my other reported issues originally and was my "wait 30 seconds" before starting trick just a coincidence?

Who knows.

but now I need a maf.
mines a Hitachi maf, HOW BLOOY MUCH!!!!!!!!!!!!!!!!
can i run a different type of maf in this vehicle and save some pennies?

cheers
Nick