I want to sort this once and for all.

[Goran]

Here are some more throttle valve related pages. The fly by wire system sounds very complicated.
The tests on VCDS using Adv. measuring blocks simply replicate (read the same values) the that the dealer's ultra expensive tool would read.
So for the Throttle Valve test described in Elsawin you pick the appropriate measuring blocks in VCDS and look up the results on the Elsawin table to see if it is within range or not. Thats my understanding at least.

[HPsauce]

Interesting.
That seems to suggest that the fundamental things you can do are:
1. Check the throttle pedal position sensors.
2. Perform the throttle adaptation.

I know this thread isn't about my problem, but as it happens I've done both of those. Fairly easy using VCDS and the Ross-Tech Wiki explains it all quite well.
In my case the pedal sensors seemed to change in value as expected when I moved the pedal. And the adaptation made hardly any change to the stored values, i.e. it was OK before.

There doesn't seem to be any test (other than doing the adaptation) that the throttle is moving correctly in normal use. Presumably you could monitor the sensors (G187 and G188?) but without knowing what the control system was telling the motor (G186) to do that wouldn't tell you much.

[Norretal]

It could be all that cheap petrol you keep putting in it?

Sorry fella, couldn't resist, hope you get it sorted soon.

[HPsauce]

Originally Posted by HPsauce

didn't realise it was so obvious and accessible just under the plastic engine cover. (

Just to close this diversion down, I replaced the Fuel Pressure Regulator this morning - details here: http://forum.a8parts.co.uk/showthrea...7229#post77229
All OK initially, just been for a short spin. Follow-up in the other thread.

[Bandycoot]

I took my scan results down to Audi and they said it pointed very strongly to the throttle body. They suggested a new one but at 900 quid I decided not to. I spoke to Dave at A8 parts and he said the same thing. Throttle body. So I bought one from him. At 100 quid this was a much better option. I fitted it the other day and............ no difference.

Something would appear to be knocking the throttle body out of adaption but I just cannot find what it is. Things are much better since replacing the fuel pressure regulator i.e. I usually only get the lights coming on once and when I cycle through the ignition it is generally ok after that. I sometimes still an annoying surging in the throttle at idle and at cruising. but this is also cured by cycling the ignition. I'm wondering are the two issues linked. Also, considering the replacing the fuel pressure regulator made a big difference could this be a fuel related problem?

[HPsauce]

Originally Posted by Bandycoot

I'm going to get the fuel system pressure tested and see what we get

Did you do that? Before and/or after replacing the FPR?

[Bandycoot]

To be honest I haven't done it yet. Still trying to find someone who can. Out here the only people with all the right equipment necessary to do most tasks are the dealers and the waiting time for getting anything done at Audi is about two months.

[Nuisanceneighbour]

Hi Guys

Not a regular poster on here but have been monitoring this thread and others describing similar symptoms with interest having encountered almost identical behavior with my 1998 PF S8.

Problems began around 2 years ago during a signature British summer-time downpour, whilst moving in moderate traffic the car felt sluggish and laboured. At first blaming a new pair of thick-soled shoes denying me the usually tactile feel of the cable actuated throttle, panic truly set in having driven through a large puddle on the nearside of the carriageway illuminating the ABS, ESP and CAT warning lights as well as the dreaded PRND234 in inverse lettering.

Restarting the car at the side of the road cleared the warning lights but performance remained hesitant and unresponsive.

Directly arriving home I read off the 3 reported faults (16505 Throttle valve potentiometer G69 - Implausible signal, 18265 Load signal - fault message from engine control unit, 17087 / P0703 Brake light switch - intermittent)

The trend was set from this point, every time it rained I could expect problems at least for the first mile or so. At first suspecting a problem with moisture/tracking the theory was disproved when exactly the same behavior occurred whilst overtaking a bus on a perfectly dry day.

Having initially tested and adjusted the existing unit according to Elsawin, I decided to replace the throttle position sensor on a whim and repeat the alignment procedure. Checked the ever expendable crankcase breather hoses which although soft, appeared to be intact. The next port of call was the bulkhead box housing the various control modules on the nearside of the car which appeared to have received almost tidal punishment from the outside was found to be clean and dry inside. Dressed the electrical contacts with contact cleaner, left it to dry then re-assembled with some gasket sealer around the now weathered rubber seal. Set the engine running and had 20 minutes with a can of easy start attempting to identify any air leaks which may have developed (none were found). Any impression of improvement may have been wishful thinking as the problem persisted on some occasions yet not on others.

The real breakthrough then occurred by accident. Having religiously filled up with BP "Super "plus" 97RON under the delusion that the product offered slightly better fuel economy, the local filling station only had regular unleaded available on this day. Having continued to use this grade of fuel for a month or two I have yet to encounter the hesitation to anything like the same degree as before however I cannot say for definite that these actions have cured the problem or simply masked the symptoms. Have others had any success using different fuel/suppliers? Now I come to think of it, the problems began shortly after moving house, before which I had always used Shell products. Coincidence no doubt!

Without drifting off topic too much does anyone know if filling stations have a separate storage tank for their "premium" fuels or is the product sold as regular unleaded with an additive delivered at the pump?

Mike

[HPsauce]

Welcome. Interesting details there, but being PF without the "fly-by-wire" throttle probably a bit different in cause.
Water ingress sounds relevant; have you looked under the passenger footwell floor as well as the ECU box under the bonnet?

Premium fuels are definitely separate, there's far more than just an additive between say normal Shell 95 and the V-power Nitro+ products.

I have seen reports of different behaviours with different brands of premium fuels; most here seem to try to stick to Shell.
I've used Tesco Momentum quite happily a few times and BP 97 only ever once.

[Bandycoot]

The plot thickens. I did another scan yesterday and all sorts of horrors have now turned up. Take a look at these:

9 Faults Found:

17972 - Throttle Actuator (J338)
P1564 - 35-10 - Under-Voltage during Basic Setting - Intermittent
17579 - Angle Sensor 2 for Throttle Actuator (G188) Implausible Signal
P1171 - 35-10 - - Intermittent
16514 - Oxygen (Lambda) Sensor B1 S1
P0130 - 35-10 - Malfunction in Circuit - Intermittent
17538 - Fuel Trim; Bank 2 (Mult)
P1130 - 35-10 - System too Lean - Intermittent
17536 - Fuel Trim; Bank 1 (Mult)
P1128 - 35-10 - System too Lean - Intermittent
17953 - Throttle Valve Controller
P1545 - 35-10 - Malfunction - Intermittent
16486 - Mass Air Flow Sensor (G70)
P0102 - 35-10 - Signal too Low - Intermittent
17950 - Angle Sensor 1 for Throttle Actuator (G187)
P1542 - 35-10 - Implausible Signal - Intermittent
17796 - Control Module Malfunction - DBW Throttle Monitoring
P1388 - 35-10 - - Intermittent

This throttle body is still showing the same fault codes as the one it replaced so I'm not convinced it's this. I'm going to have the electrical connections checked on the throttle body and the MAF, this was new six months ago, as the Ross Tech wiki says this could be a cause of these fault codes.

I'm more and more getting to the opinion the fuel injectors are on the way out. After almost 300,000 kms they are entitled to feel a bit knackered. The fuel trim fault codes suggest faulty injectors could be the cause. I'm getting a lumpy idle and I'm down on power which could support this.

As for the lambda probe, B1 S1, which one is this? Is it the pre cat lambda on the left hand bank as looking at the engine from the front of the car?

I took the car out today and the only the Traction control and ABS lights came on and then not all the time. in slow moving traffic they would come on when I stop and would go out when I moved away. One interesting thing happened a few hundred yards into my journey. I had just gone slowly over a speed but and was moving away when the engine just cut out. It started again easily but it had never done this before.