I just recently bought an '00 S4 B5 with 90k miles on it. It has awesome pickup and acceleration at lower RPM, but it seems to hit a lull at around 4000 RPM and above. My check engine light is on with the following codes:

P0441 - Evap. Emission Sys. Incorrect Purge Flow
P1136 - Long Term Fuel Trim Add. Fuel Bank 1, Sys. Too Lean
P1138 - Long Term Fuel Trim Add. Fuel Bank 2, Sys. Too Lean

Do you think the "Sys. Too Lean" codes might have something to do with the power loss? Here are some of the corrective actions suggested my Mitchell for P1136 and P1138:

-Road test vehicle (fuel in engine oil)?
-Check fuel pressure
-Check mass air flow sensor
-Check O2 sensor before/behind cat
-Check evap. canister valve

Also, the passenger-side turbo makes a high pitch whine - sounds just like a police siren. It sounds cool but is it supposed to do that? Do you think that the power loss problem might be from the turbo or just a lack of fuel pressure or something? I hope its the latter..

Thanks

 

Check out this page I found... http://germancarwiki.com/doku.php/au...ommon_problems
it has 2 short videos on it that may help you determine your sound issue. I also think it helped me to determine the issue I have with mine...bad ABS module or ECU. (Ouch)

 

Thanks! That video demonstrating a bad Throttle Body Boot sounds just like my car. I think I ought to replace mine. Luckily its one of the cheaper-to-fix problems. Maybe this is causing the lack of power too?

 

No problem! Could be?

 

So I took it back to the dealer I bought it from and they hooked up the live diagnostic tool to his computer and watched the live voltage readout from the O2 sensors. The secondary O2 sensor (behind the cat) was showing a constant high voltage meaning it was reading as if the exhaust was too rich. The mechanic was explaining that the output should constantly be fluctuating from lean to rich every couple seconds because the car is constantly monitoring the exhaust gas and adjusting the fuel mixture in real time. My O2 sensor was outputting a constant rich reading to the computer which winds up leaning out the fuel mixture, which could be the cause for the P1136 and P1138 codes. I'm going to replace the sensor and I'll let you know...

 

Have you done a boost pressure test? AWE sells one and they also list the parts to make your own:

http://www.awe-tuning.com/pages/shar...ssure%20tester

Your high-rpm sluggishness sounds like it could be a boost leak. Also, be careful running lean -- you can burn a hole in your piston if you're running *too* lean.

Regarding your O2s, I find it strange the Audi mechanic is telling you that your post-cat O2s are causing the problem. I am almost certain that the post-cat O2s are in place strictly to report emissions quality and monitor any performance issues with the pre-cats. They should have no impact on the air/fuel mixture whatsoever. Do you have a VAG? Check both of your primary O2s -- they are more likely the culprits for running lean.

 

Thanks meat - I'll try that pressure test. This will pressurize the entire intake, turbos, and intercooler? There should be no leaks at all?
And I dont have a VAG tool. Frankly I'm not really sure what it is. Is this something I plug from the car to my laptop? Where can I get one?
As far as the O2 sensors go, I made an appointment to get that secondary one replaced for tomorrow, and it's gonna be around $450. If you think it's not that then I'm really wasting my time and $$. I'm going to see if I can get a second opinion today at an actual Audi dealer, but there we go again with the time and $$ thing...

 

secondary O2 sensor has nothing to do with fuel control. it will only set a catalyst code. and with a pressure test, there will be bleed off, you cant just hook it up, put pressure to it and expect it to hold. im guessing it is a bad MAF or a boost leak somewhere as well.. maybe a bad fuel pump or a clogged filter..

man, how do some technicians have job?? dont spend 450 on the secondary sensor. it will not fix your problem.

 

Agreed, cancel that $450 **** -- and go to a different mechanic. But first, tell him he's a moron and that the down stream O2s have nothing to do with A/F mixture.

Also, I overlooked this before...is it like you're accelerating, boost is good, etc...then it feels like the engine suddenly cuts and almost all power is lost for a second? If so, that would likely be your EGT(s). This symptom is usually seen when you're really getting into boost at higher RPMs (3k+).

VAG scans the ECU for codes. You can get the software from rosstech.com and you can get a cable off of ebay.

 

i even had 2 primary O2 codes and my car ran perfect. well, to me it did, was no noticeable bucking or running rich and boost erratic. but yeah, sometimes those EGT's will go bad, and not leave a code. you just have to watch for the temp spiking. these EGT's can only tell temperature at a certain range. so check for codes as well, if no codes, then log everything with vagcom or ecu-x (which you can use the cheaper ebay cable, although ecu-x itself may be difficult to get ahold of) and see if the EGT's glitch high temp when your car starts acting erratic.

funny, i was pissed at EPL for my car not running right on a stage 3 tune, i swore it was something to do with the tune. where the car had set for so long, the EGT's i guess got a lot of humidity and moisture in them (engine sat for about a month). tony helped me diagnose bad/glitching EGT's. one went bad, drove perfect for a week then the other followed suit. gottem both at shokan for 125 a piece plus shipping. still going perfect.

lol...sorry tony, thanks again for your understanding and help.