Slight hesitation at low revs
 

Hi all I have a 99 plate 4.2 Quattro sport.

It seems to hesitate under 2500 rpm it goes very well above 3000rpm.

Any suggestions on anything to look at?

Thanks in advance.

Have a look at some of the threads in this section - there are a few discussing similar/same issues. I know that HP sauce (a member) has a thread about a mile long on this! +++

A mile long and going nowhere..........
(The last suggestion was that it was related to torque converter slip vs lockup which is "locked" in tiptronic mode so potentially testable. Nothing conclusive as yet, but my symptoms, which have been absent recently, may be different anyway).

I have read your thread a couple of times:D

Mine is hesitant in all gears, in auto or tip until you start getting the revs up, over 3000rpm there is no problems at all.

It can sometimes be worse when it's cold for the first few minutes.

Broken intake manifold switch over links?

Or faulty coolant temp sensor - I had that and it caused all sorts of oddness, but especially difficult starting.

No problems with starting and it idles fine.

That gets my vote. The 3-stage manifold flaps operate/change over at 3360rpm (and 5200rpm).

Sounds expensive? is there an easy way to check?

Very easy to check, think it's in engine stickies. Just pop the engine cover off (4 turnscrews) and look at the links. 1 minute initially.
If not broken check they actuate when the engine starts.
See: https://store-lyr7tp5r.mybigcommerce...e_Link_DIY.pdf

Nice one HP, I will have a check of that at the weekend.

See also:
http://forums.audiworld.com/showthread.php?t=2801728
+++

See also this thread -
http://forum.a8parts.co.uk/showthread.php?t=8252
And this video that Marcin posted showing how the arms work when you start up
https://www.youtube.com/watch?v=O09x...ature=youtu.be

That's Brilliant Info, Thanks guys.

Much appreciated.

Where can the arms that break be bought from? or could they be made if you knew someone with a machine shop?+++

You can still get them from Audi and aftermarket ones are available on ebay. But the flimsy plastic arms are designed to break if the mechanism sticks, so check that before you fit new arms.

The link I posted came via the Gruvenparts web site; they sell the forged metal ones.
And some people here have had spares of either the long (A8) or short (S8) ones.

But first check that:
a) the plastic links are not broken
b) the flaps move freely when you push the levers by hand
c) The bellows actuate as they should when the engine is started/stopped and revved.

Let us know what you find, or post photos as others have done. Might all be fine there - mine were despite thinking that might be the cause of my odd symptoms.;)

Ok thanks guys, I will update when I have had chance to have a look.

Similar system to my last car which dare I say it was an MG ZT190 (it was only a stop gap car before I get shouted at :ROFL: )

Except that uses small electric motors to open the flaps but the flaps snap very easy. But very similar symptoms of no torque under 3000 rpm.

If the flaps have seized is that much of a job or a major head ache?

If the flaps have seized then you'll either have to try the method I highlighted on the thread I copied which was from one of the US sites (involves cleaning out the flap pivots with the manifolds still in place) or else remove the manifold and get it refurbished fully - Daviesbike on the forum here offers that service. +++

Hi all. Just had a chance to have a look and my engine seems different to the ones posted earlier.

Only one actuator. Here is a quick video if it. I presume it's working ok?

https://www.youtube.com/watch?v=dk9bgy-ufRk

Also just hod the codes read, here is what cam up.

17800 Camshaft position sensor bank 2 (G163) open short to plus : P1392
18010 Power supply terminal 30 : voltage too low : P1602
17087 Brake switch B circuit malfunction P0703 Static - no indication on display.

I cleared the codes and 17800 17087 both came back the other one did not.

Any thoughts?

Are you 100% sure; can you show a bit more of the front of the engine in a photo or video?

See also: http://wiki.ross-tech.com/wiki/index...0/P1392/005010

Is the brake switch error just the silly one that clears if you press the brake pedal once after turning on the ignition but before scanning?

The other code is probably historic: http://wiki.ross-tech.com/wiki/index...0/P1602/005634

Only picture I took.

http://i910.photobucket.com/albums/a...525679_HDR.jpg

That's PF 32V car, 1999 registration was what through us off. Must be late 1998 car that was registered in 1999 so 1 actuator is correct. Flaps usually don't stick on 32v and does not brake links. So the fault must be somewhere else.

Yeah My bad, It's a very late pre facelift I think.

Does the valve suck itself in when you start the car up?

I'm not sure on that as my wife videoed it while I started it.

Looked at that link with possible symptoms of the camshaft sensor and I dont have those symptoms, well not sure about the emissions.

Could a dodgy sensor cause my hesitation?

I think my fuel consumption is pretty good for a big v8.

you fuel consumption would be good. . . if your engine was running lean due to fuel starvation or maf issue etc

Video is good, it looks like it's working as it should. :cool:

Might sound like a stupid question but I'm no mechanic:Confused: but could bad plugs or 95 ron fuel cause my problems?

Absolutely and even more if combination of both. If You have VCDS look at measuring blocks for 'knock retard' or something similar. If you get any values other then '0' in there under acceleration it might very well be the case. Even if it's all '0' it still could be plugs but not the petrol. While you are there might as well check measuring blocks for misfires.

No VCDS as of yet I'm afraid.

Am I right in presuming that it takes a good few hundred miles for things to correct themselves when you change to a higher octane fuel?
Also what are the recommended plugs? I will have a look at mine tomorrow.

Just solved similar after two years of this intermittently.
The rubber connecting airbox to the link pipe that leads to throttle body had split under the hose clamp so was hidden during casual inspection. The throttle body end of the same pipe had the same issue. The consequent airleak was intermittent but would cause hesitation at low revs. gaffer taped it this afternoon whilst awaiting new rubbers and problem is gone. At last.

HTH

Bill

I don't suppose you could get a picture could you.

I haven't done anything to the car because just not had any spare money lately but I have been using a higher octane petrol.

The car is very brisk when cold but the problem rears it's head when warm now.