severely lacking power - any ideas

[batty]

hi chaps - any informed opinions on this problem...
since picking up my car, I've felt its lacking power at lower revs. its most noticeable at 2000rpm in 5th gear at 60mph. if you hold it in gear and hit full throttle (but not kickdown) the engine farts around and really struggles to pick up. in auto mode, its not really noticeable as the transmission changes up a gear or 2. after 3k to 3.5k rpm full power seems to be achieved and the car sets off as expected like a screaming banshee.
there also seems to be a bit of popping, farting and misfiring at a standstill and while blipping the throttle.
any ideas ??
i'll be taking it to the local main dealer as its still covered on audi warranty, but am interested in hearing your views. and possibly in anticipation of the dealers having trouble diagnosing...[/b]

[Shoppinit]

Difficult to tell what's going on without diags. Have you got a vagcom? A worthwhile investment if you're an RS6 owner

Without the diags, it'll all be pure speculation, but sounds like it could be unmetered air getting into the engine (at least the idling / popping thing.

Is your MIL on? Does it work? I've heard of their LEDs being unsoldered to "resolve" problems

[batty]

sorry - MIL - whats that ?

you could be right on the unmetered air - it feels like a pipe off somewhere. once the demand for air increases, it feels like a switch is thrown and its off..!!

it could be related to the last work done by audi which was the cam cover gasket replaced. or previous to that the engine out for gearbox replacement.

[Shoppinit]

You can get a spray from Audi (G001800a1 leak detector) that you can spray in the engine bay. The spray prevents ignition, so you can tell if you've got an intake leak if the engine tries to die.

MIL = Malfunction Indicator Light = CEL = check engine light

[darrenswift]

My old Audi TT 225 had a similar problem, in that it would hold back under acceleration then shoot off down the road at an amazing speed. I remember wishing at the time that it would always accelerate that quickly, but after a quick call into GSF on Tritton Road in Lincoln, I ordered a new MAF sensor and the car returned to its normal self!
Perhaps it may be something similar happening to your car?
Swifty

[deanobeano]

HI Steve

I'm not sure if this helps, but after the car had the gearbox replaced (which IMHO disturbs alot of the engine hoses etc) I could hear a noise which sounded like escaping air - imagine putting your finger over a bike pump and then depressing the pump - like a pup pup pup sound. I could here it more when driving past a wall or side of a building, at low speed, with the window down. It only occurred when under load, ie accelerating slowly up a hill.

I got audi to check it out, thinking it may be a loose I/C hose. They reported back all OK, no fault codes etc.

The noise seemed to be coming from the drivers side of the engine.

I couldn't reproduce it whilst stationary.

Hope this helps

[batty]

thanks for that Dean
i think it could be related to the engine out - like you say there's a lot of disturbances and it only takes one pipe to be left loose on its clamp, etc...
personally, i don't think its major like an intercooler, as it seems totally on form at higher revs. in fact its very entertaining..!!
the other train of thought is the MAFs, like darren is suggesting. i don't think they've been replaced yet & they are renowned for "going off". i just hope the dealer might realise that, as there's no fault code from bad MAFs (not that i have no faith in dealers..!!)
but anyway, it'll be interesting to see what they find, and how it feels on top-form.
i think lincoln audi have still got the other silver plus for sale & i know its very rapid (i'm convinced its chipped as its so savage), so will tell the master tech "i want it to go like that one". at least they can't say - "oh, it'll never go as well as that - its chipped".

[Shoppinit]

Could be intercooler, since at higher engine speeds the increased flow generated by the turbos will compensate the hole in your intercooler. In fact, if you hadn't mentioned the idling problem, I would have suspected the IC first.

It sounds like you've got a vacuum leak somewhere. The vacuum tubes are notorious for rotting away (see DavePerc's thread) and this will lead to problems with the whole fueling and boost control system.

Good idea with the Lincoln Audi RS6

[batty]

the dealer has taken a look at it, no fault codes, MAF values are as expected, and nothing out of place on the piping below air intake. and says it drives as expected.
and strangely, it seems okay to me now...!! don't know if its an intermittent fault or an intermittent "i've got a new car, there must be something wrong with it" mentality.
hmmmm, what course of action to take..??
- self-diagnosis using vagcom (have just bought a licence)
- take to a specialist
- get a few more miles "under my belt"
- have it remapped.

i guess there's no real urgency - just treat it as an educational mini-project.

[Daveperc]

I think you just answered your own question!

My order would be 3, 1, 2, 4!!

Dave

[tartan_rob]

Pressure test. Unless the hose damage is very obvious you could spend weeks looking for it - and I mean that.

[Shoppinit]

You need to use your vagcom to log the specified and achieved boost levels. This will tell you if anything is out of whack. If you're making full boost, then it's probably all in your head (like me )

Log the following: (in turbo mode)

Code: Select all

Group A:	'002				Group B:	'117				Group C:	'118

Code: Select all

Group A:	'005				Group B:	'054				Group C:	'115

Code: Select all

Group A:	'002				Group B:	'114				Group C:	'115

That'll do for a start

[batty]

thanks for the suggested log schedule
i got the license for vagcom last night and did a little exploration, although i'm way down on the learning curve.
i measured 0-60 time of 6.0secs (a little slow but it was wet & muddy), 0 - 100 of 12.66 secs and 30 - 70 of 4.6secs (measured from a steady 30mph in sport mode, flooring it up to 70.
one thing i noticed was the 2 MAF readings varied by up to 35% - that doesn't sound healthy to me.
anyway - i'm off for a bit more logging....

[Shoppinit]

Your times sound like mine, and I got 462PS on the rolling road. Go figure.

My MAfs are 10-15% different from each other. 35% sounds like a lot. YOu should log the groups 32 and 33 (I think) to find out what's going on with your lambda sensors. You may be approaching the upper limit of what they can adjust.

[Shoppinit]

Check 20 and 21 for ignition timing, too Too much information!