Audi S4 B6 - What can go wrong?

[Dr G]

Welshbeef said:

It’s the same 4.2v8 unit as the C5 RS6 which has 3 year replacement cycles.
Turns out also from further replies even though it is a cam chain now frankly it also needs changing to avoid a big fail cost.

C5 RS6 engine is quite different. That's a development of older V8s (at the time by Cosworth) whereas the S4 engine was worked over quite heavily to fit into the A4 engine bay. They don't even share a block/capacity.

[Dr G]

AudiSport said:

3.2 V6 FSI?

More closely related to the aforementioned rattly V8s and suffers the same issues.

S4 is a fun and characterful car but worth finding one with either the work done or budgeting to do it yourself. If you can buy it a little cheaper and invest in the chain job it's still a lot of car for the cash. Not a lot else like it on the market regardless of price.

Not worth doing if you're the type to change cars frequently, though.

[Welshbeef]

Dr G said:

C5 RS6 engine is quite different. That's a development of older V8s (at the time by Cosworth) whereas the S4 engine was worked over quite heavily to fit into the A4 engine bay. They don't even share a block/capacity.

Is there any engineering reason why Audi stuck with 4.2v8’s be it petrol or diesel

[catso]

Ray Singh said:

I have access to a VAG code reader - VCDS - would this show what the problem is?

Probably, I recently had a 'cylinder shutdown' on my S4, VCDS showed cylinder 5 misfire as the cause - It did it twice so I changed the coil and it's been fine since.

I then discovered that I could log misfires on a journey if VCDS/laptop left connected which I did and although it would have been useful to have done that before swapping the coil, I've not had the problem again and since swapping the coil was a little tricky for access reasons I'm not about to put it back for a confirmation.

I'm pretty sure taking it to a dealer would have cost me significantly more than the £30 a new coil cost...

[Dr G]

Welshbeef said:

Is there any engineering reason why Audi stuck with 4.2v8’s be it petrol or diesel

The design was born (very loosely) from two contemporary 1.8 4cyls stuck together (3.6 litres in the original Audi V8). It grew from there. Like a lot of manufacturers there are design similarities to its other V engines.

The engine had several major design revision over the years for power, economy, emissions, fitment blah blah blah

Audi sort of gave up when they got to the B8 RS4 (it never even got stop start) as the engine by that point needed a blank canvas to keep up. They're now replaced by the Porsche/Audi turbo V6s.