I've recently noticed a very verysubtle "chugging" at certain RPM's, when driving at a constant throttle. It's more noticeable while cruising in 3rd or 4th gear, between 2500-3000 RPM (or near there). Even under hard acceleration I can feel a slight slight lossof power within that range, but then smoothing out beyond then.My gas mileage has been pretty consistent since I've owned it: 250-270 MPT (city, w/ a.c.), so I'm wondering if that's related.

It almost feels like a misfire, but I'm not sure if it's the coil packs or just the plugs (I just recently had the coolant temp sensor replaced, so I think the plugs might be a tid-bit fouled). IMO it's not fueling cause if it were a clogged filter or injectors it should be noticable across the board, and the car still flys otherwise.

On a side note: Since I've owned the car it has always a little excessive "engine shake" when the it's shut off.I'vealways been puzzled by this, and the Dealer says there's nothing wrong. So I'm not sure if this is just an "S4 thing",or my mounts are bad, or it's a miss-fire related symptom...

Does anybody have any ideas, or similar experiences? Let's go Cert-Techs!

Thanks.

p.s. the car has only 1 mod, has never been modded otherwise, and has only 17.5k on the clock (orig.); it was only garage-kept by the 1st owner.

 

Vag-com for stored codes. May be a boost leak, or a coil pack going bad.

My car doesn't shake at all, when shut off. Can you explain this some more? Is the engine not wanting to shut off? Or does it just shut of rough? How about when it starts?

You might want to check & make sure your motor mounts are not leaking.

 

So it could be running like g-bage from a misfire or boost leak, and not trip a CEL??? Damn that sucks! I'll see if this place nearby (German Motoring) can do a diag. w/ Vag-com. This might be a dumb question but... will the Dealer use Vag-com or do they have something else to scan for hidden codes?

As far as the shaking is concerned: It only happens right after the key is shut off, and the engine internals are coming to a rest; it's very brief, but noticible. It doesn't keep running or anything (like it doesn't wannaquit), butjust acts like something is unbalanced or a rouge plug is behind schedule. Start-up seems normal I guess, but definitely nothing like shut-down.

Do the engine mounts reallyhave fluid in them, or were you just being facetious? How can I tell otherwise (visually)? I'll search more on it, but is this a fairly simple swap (assuming I have access to a lift)?

Thanks![sm=hail.gif]

 

Yup, it can run rough & not throw a cel, but there should be stored codes.

The dealer has a Vag-1512 (or something like that) tool, it's a factory Vav-Com. Any German repair shop better have access to a Vag tool, if not, don't go there.

Yup, the motor mounts are in fact liquid filled, it helps absorb vibrations. They do in fact split & leak, some times the mounts are even in 2 pieces. You have to jack up the car, I look around the mount, you can also put a jack under the engine (on a 2x4) & lift it up a little, this will give you a little more peek inside the mount.

 

Nice! Thanks 2K, I'lltry all that.