Please help me with this problem!!!

[Jamie]

I promise not to ask again, as it is probably the 100th time i have done so.

I get a severe juddering under boost every now and again - 3,000 rpm. It did it a few times last year. Had the lambda probe changed - didnt do it again.

Its started doing it more regularly over the last 6 months, and particularly in the last 4 weeks. I have had the regulator (potentiometer) changed 2 wks ago - the device which tells the car which position the throttle is in. It was also fully checked for boost leak.

I drove to Le Mans this w/e, and drove pretty hard. Approx 200 miles into the trip, it did it again. I was with a friend who had an s2 with the same problem and he said to pull over, turned the engine off for 5 mins and went off again. the problem seemed to be cured.

Therefore, it seems to me that is electical, possibly the ecu - ie, when you switch off the engine, something is re-set and the car is fine again.

can someone out there please give me some kind of definitive answer. Its driving me mad and I cant afford to experiment changing parts all the time. I know there are always a number of potential routes to each problem, but this is quite a significant one, we've checked a number of the obvious things and i still have a car that is not performing.

Im particularly annoyed as i got burnt off from the toll on the A26 out of Roun by a Mazda MX5!!!

Thanks.

[quattronutter]

3b or aby?could be coil packs if aby,or ht leads if 3b starting to go...

[merlin's S4]

Yep sounds like a coil pack to me if it's an ABY!

[Jamie]

Yes it is an aby.

so you suggest i give that a go? does it follow then that if i turn the car off for 5 mins, then restart, the problem is cured temporarily?

[S2central.net]

Doesn't follow at all IME guys... Dodgy coil packs cause misfires and hesitation. It is airleaks which cause overboost protection to kick in.

Jamie you need to get the intake system pressure tested for leaks. Properly performed, this one test will determine the source of the leak. A visual check will only find obvious splits. Oh don't forget to check that the spark plugs are nice and tight - but not too tight or you'll do thread damage. Go for 25-30Nm torque on them.

Depending on the cars mileage, and when you *know* the following cheap items were replaced, then I thoroughly recommend you do them for happier running.

WGFV - needs to be airtight and capable of operating as fast as the ECU requires
TBV - get the S3 variant with part number ending in 710N
Fuel Filter - very easy to change on the Coupe

For a little more money, its also wise to change the Lambda probe - these things only have a life of 60k miles.

You should really pull blink codes or find someone local on the forum with VAG-COM. At worst there's a couple of gatherings planned over the summer, so if you get along to one of those, you can get checked into the S2 health centre for some fault finding.

Paul

[S2 Ant]

That problem of juddering is exactly what my car was doing when a coilpack was failing.... drove ok-ish until the boost climbed a bit in to positive figures, then got a juddering, felt like driving over a very harsh road, bit like when you drive over the yellow lines in the road when approaching a junction, only more harsh.

I lived with mine for a couple of weeks, cos it meant i drove sensibly, but i got p'ed off with not being able to gun it if a car tried it on so took the plunge.

[AbsS2]

^^^ Ive got the same problem now too !!!!

Know any one that does cheapish Coil packs?

[Jamo]

^^^ Ive got the same problem now too !!!!

Know any one that does cheapish Coil packs?

Euro Car Parts mate.

Jamie before you look at coil packs, get all the basics done first, make sure you aint got a boost leak and get the Mark H Intercooler mod (70-60mm reducer pipe).

[S2 Ant]

I paid £58+VAT each for my coilpacks from ECP.

[SR71]

Something you also might like to consider are the knock sensors.

The symptoms that resulted in me having to change my ABY knock sensors were odd.

I'd get full/correct boost in all the gears until the car generated a frequency that the knock sensors interpreted as knock. I assume thats how they work?

From that point on the car would not boost above ~7psi.

If you flipped the ignition on and off (whilst moving) you could reset the ECU and you'd get full boost back...until the next "knock" event.

I never got any juddering as such but the car just felt it was down a 100 ponies.

It tended to happen initially in fourth pulling away from the lights once the car was warmed up but had been sitting idling for a while i.e., everything getting nice and hot.

Changed the knock sensors and everything was instantly back to normal with full boost available all of the time.

Looking at a knock sensor though, you'd think "What can go wrong with that?"

HTH.

[S2central.net]

I was interpreting 'juddering' as being a fuel pump shutdown from overboost protection... but if the juddering is more like a consistent on-off-on event then I could say its more like an ignition problem as opposed to fuel shutdown.

Must admit my memory of fuel pump shutdown is normally at 4k rpm so that's inconsitent with problems at 3k rpm.

As for knock sensors - they are *supposed* to cause subtle retarding of ignition on the detection of knock and if things continue it should trigger boost reduction. Knock sensors are notoriously hard to test of course - as the man says - what's to go wrong... but like many Motronic items, they only throw up fault codes when disconnectd or short-circuited. Seemingly a crap signal from one doesn't get perceived as a fault by the diagnostics.

Another candidate is the primary ignition amplifier - theres two on the ABY which supply primary voltage to each coil pack. A duff amp or coil pack will give you misfires.

A quick easy check on the ignition system is to see that the earth strap from the coil packs (at the bulkhead end of the engine) is properly secured to the cylinder head. I've encountered a couple of ABYs with misfiring that were purely attributed to that being loose - causing bad earth for all coils !

I would do the leak test again - just to be absolutely certain about that - then the cheap items I mentioned. Test the coil packs - you need a nice DVM with the ability to read very low conductance measurements. If they all seem OK, then try swapping the primary amps from another ABY/AAN/RS2, and if that's still bad you could try swapping knock sensors.

Of course another candidate is just a faulty MAF and/or its connector - try swapping with another owner if you can - those bad boys aren't cheap.

Paul

[kingos2]

i ve got the same problem to started last night and got worse on the way back from castrop germany vw audi show my mate djavant and i are going to swap coil packs tonight i let u know the out come if u like

[kingos2]

fitted new samco hoses still same problem so that eliminates boost leeks kicks in at 35k rpm swaped MAF from djavants s2 still the same problem but that saves a bit of money, engine to hot to swap coil packs going to do them tomorrow now but that's what i think it is they only last about 130k miles you could try cheking your WGFV hose to the wastgate as i found out mine was an old fuel hose could'nt stand the heat of the engine and perished in my hand when took it off!

Does any one no the Ohms reading for coil packs so i can find out which one it will be thanks.

[S2central.net]

You need a fairly high spec DMM to read *conductance* values on those coil packs. There is a scpheel on www.sjmautotechnik.com - I can't remember exact values.


Paul

[kingos2]

cheers paul il check it out