musclewagon

For a quick background, i have never thrown a CEL and i've reprogrammed the TPS (thanks AchTuning), but my car still is missing power. Since first reporting on this i've tried a new fuel fitler, new air filter, new wheels/tires, new Milltek exhaust, and new plugs. Nothing has changed. I've noticed a few things though - this car seems VERY picky about the brand of fuel used, it doesn't like Shell 92 but it does like 76 92. Also, before it gets to operating engine temp it always RIPS (i've driving a lot of S4s, so i know what they are supposed to be like). Now, i never bash on the gas before its warm, but MAN this is what it supposed to feel like. I'm thinking O2s or intake air temp sensor, or something like that that does not offer a reading until the car is warm is on the way out - meaning the system runs on a program purely until warm, at which point it gives the sensors full rein to command A/F, timing, etc.

HELP - please! Any ideas on which sensor could be bad? Something else funny, is that my mpg's keep showing worse than they actually are (i hand calculate EVERY tank). Wonder if this is related?

s4for5_TTfor2

This engine actually changes the cam timing during warmup.
Pic below is the device that controls cam timing, 1 per side.
It is only in effect until warm up then returns timing to normal specs.
If it fails to operate I am pretty sure you will get a code.

Audi>A4,S4>2002-2007
4.2 Liter V8 5V Engine

Camshaft adjustment:
The adjustment of intake camshafts is load and RPM dependent. Oil pressure is switched to respective camshaft adjuster (mechanical adjustment devices) via solenoid valve for camshaft adjustment.
Note: * Camshaft adjustment is active only 25 seconds after engine start *

<img src="http://pictureposter.audiworld.com/32714/cam_adjust_valve.jpg">

DapperD

I'm new to the S4 but I have felt the car pull harder when cold...Or so it feels.

I'd be interested in other's experiences. It would be great to get my car dyno'd when cold and then after its been driven for awhle to see any difference.

Also, I get a bit of a stumble at idle. The motor seems like it should be smoother, not sure if Musclewagon experiences that as well....Or anyone for else for that matter

AreenS4

I totally confirm that. It runs ALOT harder when cold. But thats how most cars are

S4iowa

Probably getting timing retard when warm... We need to start doing logs with the vag-com

musclewagon

Yes - it stumbles at idle but only when its warm, also when totally cold it seems to take longer to start than it should (again comparing mine to the B6 S4 my dad had in 2006).

As for the cam timing device that is only operable after 25 seconds, no that doesn't confuse me. It confirms that is not the problem though. As my car is noticable faster for about two or three minutes afer intial start up, not just 25 seconds.

I believe VAG-Com is what i'm gonna need to answer my question though. As i believe this to be timing related (fuel brand change makes me think this way).

If it is timing pull that is causing the intermintent poor performance, then where do i go from there? I will need to find what sensor is commanding the timing pull?

Who can help me with doing a drive around VAG-Com?

charliemike71

jba

Where are you located?

musclewagon

Seattle area - Kirkland actually (I work in Seattle though)

bhvrdr

such as poor fuel, inadequate cooling, etc. If you had an inop sensor right now you'll get a CEL or throw a DTC which you can scan for.