A3 3.2 Quattro - emissions warnings and vibration

[McHamish]

Hi,

I'm new here - first post!

I've recently bought a 54reg A3 3.2V6 Quattro and wanted to ask a question...

A couple of days after picking up the car I had a couple of issues which the dealer (and his garage) have assured me are resolved/not a problem;

• The Emission Control System warning light appeared
• The car seems to gently vibrate in idle

The first issue was 'fixed' when I took it back to the dealer and he took it to his garage who plugged it up to a VAG-COM. Apparently it couldn't detect any faults, so they reset the warning light and told me to keep an eye on it. The dealer told me that if there was a fault it wouldn't allow them to reset the warning light (don't know if that's true or not!).

They think that when they took it to be MOTd it was running on empty, and as it was on the ramp with the engine running, the dregs from the tank would have gone through the engine causing the 'sensitive' emission control system to flag up a problem. I asked an Audi dealer about that and they laughed, although they did want me to bring it in and remortgage my home so they could test it themselves.

The second issue might just be me being paranoid, it isn't misfiring just vibrating gently in idle. The only way I can really be sure is to sit in another one to see if it's the same! Or another owner could tell me if their car does the same! I read on the interweb that the timing chain can lengthen over time that can cause it to vibrate, but I don't know if that's the cause; perhaps I can just get someone to tighten the timing chain.

Other than that the car's awesome! Nice and smooth drive - i just need to get used to changing gears quicker!

Cheers...any help or advice is appreciated!

[McHamish]

Well great news....the ECS warning light is back - I guess I bought a duff.

[a8 tech]

Hello Hamish.
3.2 lambda sensors before the cat burn out and require replacement and also there is a software update for the engine ecu to reduce the operating temperature of the broad band lambda probes.
the engine ecu earth point beneath the passenger side headlight suffers from corrosion causing the mil light to come on with/ without a fault code(earth voltage over 0.50 volts).
Uneven idle can be caused by rain water/steam cleaner water passing the coilpacks causing the coil packs to arc,also the plugs are often over looked and should be changed every 40,000 miles,also the coil packs do fail and sometimes its hard to tell and misfire recognition in measured value blocks will cast some light on the issue.
Also water can be sucked into the vacuum units for the exhaust flap change over flaps,this is sucked up into the inlet manifold causing irratic idle.And if the complaint is more dash rev counter than actual fluctuating engine idle the dash insert is faulty
Try to post the engine ecu software version by checking for fault codes with vag com and clean the earth points under the passenger head light (there should be 4 bolted brown wires within 6 cm area)Attachment 3435

Attachment 3436 the timming chain gives a metalic rattle when its stretched and also the camshaft sensor will read implausible signal (i would disregard the advise about the chain as it is very unlikely).However the ribbed belt tensioner and water pump are worth considering for your vibration and removing the ribbed belt to eliminate the possibility is certainly an option.
Plenty there for you to consider and this is advise not a diagnosis.Regards A8

[McHamish]

Hi A8, thanks for the advice.

I took it back to the dealer yesterday who sent me round to a automotive electrician. This time the VAG-COM showed intermittent misfires on 3 cylinders, so they are going to replace the 3 coil packs and all plugs.

To me, misfires 3 cylinders seems to be a coincidence, but we'lll have to see. Hopefully this will be the last of it.

When I get it back I'll clean the earth points.

Thanks,

Hamish

[a8 tech]

misfire no 3,that sounds more like it.

[McHamish]

Well I picked up the car from the dealer last night....they ended up replacing all the coils and all the plugs. They said that once one fails, quite often others, or the rest can fail.

It seems to be running ok now, certainly a lot smoother. It still has a slight vibration at idle (with the rev counter wobbling slightly), but it's not a worrying amount.

I'll have to keep an eye on it...apparently the coil packs are a frequent problem.

Thanks for your advice!

[McHamish]

Well it didn't last long! The light came back on.

[a8 tech]

refer to my original comments regarding the lambda probes and the eart points.
Unless they have damaged a coil pack when fitting them

[engineermk]

Well it didn't last long! The light came back on.

VAC-COM will clear the warning light (the dealer was wrong to say it can't be cleared if there's a fault).

To prevent fasle warnings the system will need to see the fault three times on consecutive cold starts before illumination the warning light. so the dealer can clear the warning light and you may not see it for 3 days even thought the fault is still there.

[McHamish]

Thanks for the reply.

The technician did snap the plastic from one of the coils, but they've assured me this one has been replaced. I'll check when I pick it up.

This time they tell me the VAG-COM has detected a fault with the lambda probe on the engine side of the cat. They are going to replace this now.

It hasn't been economical (210 miles on a full tank according to the computer), which might mean it's been running rich.

To be honest I have no faith in the garage they're taking it to, or the dealer, so I'm expecting the fault to come back! The dealer even had the audacity to tell me I wasn't protected by Trading Standards as it was a used car. When I told him I knew exactly what my rights were he changed his tune.