Vagcom Output, Opinions?

[S2tuner]

JonnyX: he is running a pre-ME7 ECU which has part number 8D0 907 551 without any suffix. Those are particularly weird and some measuring blocks are simply inexistant in them.

About going to a garage to find out what's wrong, what can I say, I think you're wrong but that's only my opinion...

[craigg]

I presume you work for MRC?

For starters i'd love to take my car to yourselves, but the fact that i'm 3-400miles away creates a bit of a problem there...

Also at the end of the day, a garage (ie yourselves) will just follow a set diagnostic procedure, testing, using the results to narrow down the testing and testing some more, until a cause is discovered.

With the correct equipment and knowledge anyone can do this, and IMO the entire purpose of internet forums like these is to share that knowledge. Perhaps with the prestige nature of these cars, people are more likely to just drive it to a garage and say "fix it please", i however like to tackle these jobs myself, where possible, and gain the knowledge and experience while doing so.

So far we have discovered the ECU appears to be cutting the throttle, my current thinking is this is either a) overboosting or b) some issue with the throttle controller.

I hope that with some poking around with a newer version of vagcom i can get the boost data, if not i'll install a boost guage and use that instead.

I realise that having installed a non-standard throttle valve PCB that this could be causing problems, so i will do a TBA, and take a look at the throttle plate position and compare it with vagcom output at various accellerator pedal angles. I'm hoping however that seen as all the throttle fault codes vanished on installing this PCB that its not to blame here.

There are some frayed vacuum hoses at the dump valves, and although not split might mean that there are more in a similar condition elsewhere in the engines pipework that's leaking boost pressure from the wastegate control system and hence not controlling the boost properly. I do plan to get these changed along with new DV's and probably an F-Hose delete while we're there just to remove the common failure points from the equation.

But i'm not too keen on ripping things apart and changing components until an exact cause for the throttle cut is determined, if it IS boost related then i'll take a fine tooth comb to the boost control systems and replace everything then, just as i'm sure you would do to a customers car.

Cheers

[jimbo1234567]

he is mr c

[S2tuner]

Craig, what you don't seem to realize is that people who are used to working on these cars day in and day out and who have worked on quite a good few hundred of these will find your problems much quicker than you possibly could, even with the help of forums. However, even if we are fanatics of these cars and only breathe by them, we do also have to earn a living, hence we won't diagnose people's problems over a forum for free, because if we did that, in the end we couldn't pay for our bills anymore and we would end up unemployed.

And jimbo is correct

[craigg]

I don't doubt your ability do be able to diagnose the problem quicker than i can, but its just not practical for me to travel so far to get the car looked at, nor can i justify the expense of doing so.

I can also understand your personal reluctance to diagnose a vehicle for free, it does however seem that unlike some of the other forums ive used which tended to be more full of people who like myself preferred to get stuck in, members on this forum seem to take more of a back seat when it comes to these things. I've never had someone on any other car forum tell me to take my car to a garage when i've had problems, and i've done all the work required to every car i've owned since i started driving, including engine transplants and suchlike. This car is clearly new to me however and as with anything, it just takes a bit of time finding my way around it.

Anyhow, i thank the members that have provided the assistance thus far, and i will hopefully get some more info and insight as to whats happening tonight!

[JonnyX]

Hi Craig,

I would be surprised if you got that much throttle cut from overboost without throwing a code. Did you try
a TB alignment as suggested?

[craigg]

Thats on the cards for this evening!

Will let you know!

[craigg]

Ok i've been out and done a TB alignment, readings before and after the alignment were the same, and it said ADP OK after it.

I also took a log of group 60 and 61 with me slowly pressing then releasing the throttle pedal with the engine off, and it seems to correctly move thru the range, and throttle drive properly goes from 1.2% thru to 100% then back:



I also took another look at the fuel trim values and got this:



Which is a bit different to the first time round...

I'm going to try and get some boost figures in a bit, but does these new fuel trim numbers mean anything?

Cheers

[craigg]

Hmm the ecu really does seem strange in that it doesnt want to provide the boost figures. I've made another log of channels 117 and 118 which are supposed to show amongst other things spec'd and actual boost. The two figures seem very close together though, so i suspect they're actually showing the same value. Not sure if that value is actual or spec'd though

It seems to peak around 1750mbar, before droping back and holding around 1500mbar. Also worth nothing that the throttle cut seems to be less pronounced this time round, the log shows 3rd and 4th gear at WOT and it seems to have managed to sustain a maf reading of 212g/s in 4th, but only 208 in 3rd probably due to the throttle cut...

I'll just link the entire XLS here, as its a bit too big to fit as an image...

http://lr90.org/Audi/S4/LOG-01-003-117-118.xls

Any ideas now?