A6 Avant Running Problems

[colinn]

Hi guys , I recently bought an S reg 1998 A6 2.8v6 quattro. I have been having some running problems with it. First of all it started cutting out at junctions which seemed to be a common problem with butterfly sticking on throttle body. I had my mechanic clean this which seemed to solve the problem. Then it started stuttering when driving , very intermittently. The fault codes showed air mass meter and intermittent lambda sensors. So I have now replaced the air mass meter , reset the codes and run it for a few days. Now when I first start it if I don't let it heat up for 5 mins or so when I drive off it loses power , sometimes cutting out.When I connect vag-com it sometimes says lambda probes intermittent.So what im wondering is would the lambda probes being faulty cause this problem or is it time to replace the throttle housing?Any advice appreciated.

Cheers

Colin

 

[The Slug]

if lambda is faulty it would be worth changing it for sure, may cause problem with fueling? Any other faults like N112/3 Secondary air valve??

 

[colinn]

Thanks slug. I have ordered a new lambda sensor from audi.

Vag-com tells me its probe B2 S1 thats faulty. Does anyone know what exhaust this is passenger/driver side ?

Cheers

Colin :thumbsup:

 

[The Slug]

im sure its bank 2 front lambda, which is driver side before the cat

 

[colinn]

Thanks again , I will post once its fitted and advise if its cured my running probs.

Colin

 

[colinn]

Fitted new lambda on driver side. Still getting error code

16538 - Oxygen (lambda) Sensor B2 S1: No Activity
P0154 - 35- 10 - - - Intermittent

I am assuming I have changed the wrong 1 so I was going to refit the 1 I took from drivers side into the passenger side. Any ideas ???

Colin

 

[The Slug]

must be the wrong side, try swapping them over

 

[Bobtech]

Yes, bank 2 is definitely the passenger side. Oxygen sensors are good for between 50k - 80k depending on whether the car is a city or open road vehicle respectively. The oxy sensor, as no doubt you know, is the last item in the engine management train and if it is;

a) switching between lean/rich every second or so
b) showing a "transit" time between the two states of less than 300msecs
c) switching within 60 seconds from cold start up

then the sensor is good and it shouldn't flag any fault codes. Unfortunately, you need an oscilloscope to see what is going on or a good EOBD package on a laptop.

Generally, if a,b,c are good then all the other management components "behind" the oxy sensors are likely to be functioning correctly.

DON'T run out buying throttle bodies, it's highly unlikely to cure your running problems. If the clock is on 80k or more, I would definitely fit new sensors first.

The engine ECM will not go "closed loop" until the oxy sensors have given good info to the ECM and as such, the car will not drive 100% until it is in closed loop condition.

By the way, the rear oxy sensors are only there to tell the ECM that the cat/cats are catalysing properly or not. They have no function to do with the running of the engine. However, if a code is shown indicating sensor 2 inactive or similar, then very often it is the catalyst causing the problem rather than the sensor.

Hope this helps.

 

[bar shaker]

The first lambda down stream will be 'wide band' and these are not cheap to replace. They are critical to the fuelling and they control the mixture during warm up, to meet the EU emission target for time to warm the cats up. The lambda after the cats are generic and can be sourced for £50, if you are prepared to crimp it to the Audi loom.

If the MAF did fail, it is possible that the cats got ******.

Before you start spending hundreds on new cats or wide band lambda sensors, I'd get a local spanner man to do a '3 gas' test on the emissions at start up and at operating temp.