Engine help
 

Every time I start the car I can feel the engine shaking, not violently but definitely noticeable. Quite embarrassing when passengers point it out. It does it on both petrol and LPG and the rev needle moves up and down just slightly, my old S8 never did this. The revs were always constant and the engine smooth. It only does it for the first 5 mins, after it warms up it is fine. Any ideas what it could be? Ben checked the cambelt the other day at Audi's in the park and said it had been put on wrong, could this contribute to it? I'm starting to feel I am just unlucky when it comes to cars now. If this is going to cost a lot I'm going to go shove it of a f\88in cliff :mad:

Vag Com says this:

Address 01: Engine Labels: 4D0-907-560-AVP.lbl
Control Module Part Number: 4D0 907 558 J
Component and/or Version: 4.2L V8/5V G 0004
Software Coding: 05753
Work Shop Code: WSC 00460
Additional Info: WAUZZZ4DZ1N003922 AUZ7Z0Y1489941
4 Faults Found:

17538 - Fuel Trim; Bank 2 (Mult): System too Lean
P1130 - 35-00 - -
17536 - Fuel Trim; Bank 1 (Mult): System too Lean
P1128 - 35-00 - -
18058 - Powertrain Data Bus: Missing Message from Instrument Cluster
P1650 - 35-10 - - - Intermittent
16955 - Brake Switch (F): Implausible Signal
P0571 - 35-10 - - - Intermittent
Tuesday,10,August,2010,20:57:13:36799
VCDS Version: Release 908.1

check your MAF sensor and hoses for operation / leaks Amar sounds like it might be an issue. The only other thing im wondering is that if the cam belt wasn't done quite right as Ben said then maybe its contributing to the lumpy running?

If its running lean then dont leave things too long and use super unleaded at all times for now

There are two ways to do a cambelt change:

1) You have the correct Audi tools, you lock the camshafts and crankshaft in the correct position, remove old belt and fit new one and tension with everything locked up - This is the proper way to do it.

2) You cut corners by marking with chalk on the pulleys what position they were in when you take the belt off, and simply try and line it up when you put it back on. This is the quickest way to do it, and sadly a lot of garages will do this - even Audi ones ! - This leaves the belt potentially a little out of sync which the engine ECU can (and does) compensate for. I'm pretty sure you can see this is measuring blocks with Vagcom.

I guess if you use method 2 too many times though, it would lead to unrecoverable discrepancies in the timing and it would be a problem.

That said, I'd expect it to be a constant problem, not something that goes away after 5 mins.

I had rough running on that engine when I first got it because the garage had left the cats off, and it had no lambdas so it got no signal and ran rough as it didnt know what its emmisions were.

I wonder if you just have a simple problem on a lambda probe?

The MAF is worth checking too...

It cant be anything serious, it'll just be some mis-information that the ECU is getting from somewhere...

oh.... and dont you threaten to push her off a cliff... Ggggrrrr.. ;)

The timing belt's definately not helpoing Amar and could explain why it's worse when cold as the valve timing is altered during warm up, but also need to look for, as suggested, duff air mass and air leaks.
keep ya chin up bud and she'll run fine in the end!

Neil, Its running V Power, that's all I have used in my S8 and this, I think the maf has been replaced recently, looks like an Audi genuine part to. Leaves the air leaks and cam belt now.

Thanks Ben, so its altered during warm up, that makes sense to. I think I will let you give it a very thorough health check when your back from Germany and get any issues that need doing sorted after pay day. Cambelt alone is £500 though and I would want to get the waterpump done and with it being a genuine part will need to add another £100 or so on to that. FFS :(

Ian, missed your post. The lambdas aren't showing any faults. Only get about 17mpg in this though whereas on the same journey would get 19 from my S8 which had fresh lambdas.

17 is about right - you lose about 10% power/mpg on LPG ?

If you are seeing 17 on petrol though, then something isnt right....

About 17 on petrol...

I bow down to Bens expertise in this area.... I was seeing about 16 - 17 mpg average on LPG on a long run, with 19 - 20 on petrol on a long run (I only ever did long motorway runs). I guess if 17 on petrol is a mix of driving types its probably no worse than when I had it....

I didnt notice any vibration though.... :Confused:

I'd really like to know what Ben finds as its never missed a beat with me, although I guess I didnt go straight from another S8 into this one, so dont maybe have the direct comparison you do....

That's with mixed driving, 65% motorway and 25% town. I hardly every push the car, get 20.5 on the motorway on a long run, used to get 22.5 in the S8.
As soon as you start it, the shaking is quite obvious. I was so embarrassed when a friend pointed it out and had my fingers crossed he wouldn't notice as he knows how much I paid for it. Boy was my face red when he said 'why the hells it shaking like that for' Only does it on idle.

Engine mount?

Scrap that, as I have re-read your post.

engine misfire
 

if all is fine when warm...then ecu is on closed loop and all sensors are responding fine....if lambdas are reading lean fuel....then it means either lack of fuel or too much air....in which case ecu would compensate by introducing more fuel...thus the poor fuel economy....

if timing was out then u would get misfire at all times not when cold....

judging by the condition of the discs when u bought it the car has been standing for a bit ...my first act would be clean the o2 sensors (or replace em wit the s8 ones) , maf...

remember when ur running lpg...it is tough on components...and can sometimes leave a glazed coating if not fully combusted....

my guess is the one of the pre-cat o2 sensors is duff....

Perhaps its terrified after hearing about what happened to your S

It's vibrating worse now when it's hot and when cold. Very noticeable, a little lumpy when accelerating at low revs to. On both petrol and LPG. Got 200 miles on LPG and not 230 as usual.
My brother in law vag commd it for me as I was tired after coming back from Germany and he said one of the pre cat lambdas was reading out of it's values, but no engine management light.
Can you guys please suggest something as I just cannot do without a car.
I'm going to see James (mkoneman) on the weekend to see if he can find anything but any suggestions till then would be greatly received. :(

Just doing some bedtime reading here...

Did you find out what the problem was?

MG

Just a coil pack that was on its way out. :ROFL:

Had the cambelt re done and fitted correctly too, as it had been Tipex'd on by the previous owner, I hate botches on cars like these.