I have been reading this forum for some time but have just registered since I now own a 93 S4. I have only had the car a few weeks. It is silver with black interior and has 101K Kilometers.

Mods done by previous owner: TAP stage 2 chip, Samco intercooler Hose, Stiffer wastegate spring and modified air intake.

The car needs a few things: Rear shocks, V-Belt Tensioner (Noisy), but other than that it runs very well except for one strange occurance. I was taking a friend for a ride and the following occured:

2nd gear reving at about 5500 rpm and suddenly the car backs off hard like a speed limiter kicks in or something. It's like the car starts bucking. It's as if someone pushed the clutch in under heavy throttle. It did this 3 times during the trip in different gears.

Since then I have not driven it very hard and the problem has not re-occured. The clutch and transmission seem to work fine. I am not sure if this is a result of a failing component or the engine computer system sensing a problem and automatically backing off to protect the car.

I sure would like to hear from anyone else with a similiar problem or any insight.

Thanks.

Peter Schoettle
93.5 S4

Most likely it's this: Under the strut tie car is a large (2" x 4" x 16") plastic cover that has 2 plastic screws on top. Turn the screws 90 degrees with a dime or something like that. The cover will lift off. Towards the driver side of the car you will see a small component with 3 small hoses going to it. One of the hoses will be off. Buy a new hoseclamp and reattach. The stock hoseclamp is not reusable.
Let me know if this is what it was. This happens to most of these cars sooner or later and it is the cheapest thing that goes wrong.
Jim
93S4

he'd be running atmospheric if that hose came loose?

his problem sounds more like he needs a 3bar map sensor. TAP doesn't upgrade the sensor with their chip set, relying on the wastegate spring...

Jim the hose will cost me nothing to check. I will let you know what I find.

Jason have you heard of similiar problems from other S4 owners with the TAP chip?

Is that they should have bought an MTM. hehe.

Because the hose I am referring to does not carry pressurized air for the engine intake, it is an auxiliary line that feeds into the ECU telling it if there is an overboost situation. It cuts the fuel when there is too much boost before blowing up the engine. When the hose is disconnected, it gives the "bad" signal to the ECU. Sorry I can't be more succinct today, having a hard time verbalizing....
Jim
93S4

Just FYI: This issue (the one I descibed above) has nothing to do with chips or boost level you are running, mine happened when the engine was stock. Merely has to do with the stock hoseclamp failing sooner or later, average is at around 70-80k miles.
Jim
93S4

I heard an UrS-car owner discribe having this problem, they had TAP upgrades...

But, Jim is correct. I thought he was referring to a different hose in pretty much the same area that also has a reputation for comming loose.

That is most likely to be your problem.

I do suggest looking into getting a 3bar MAP sensor. For some reason, TAP doesn't include one in their chip set. Any time you increase the boost levels in the ANN 20v turbo's, upgrading the MAP sensor from the stock 2.5 bar to a 3 bar is a safe way to go...

I should have a chance to look at the clamp this weekend. I will let you know what I find.

I also read the following at http://www.sjmautotechnik.com/
Overboost Cutout? ECU fault code 2224?

If you are encountering an overboost condition which is causing the ECU to cut the fuel pump, and you have stored the 2224 ECU fault code, here are some items to check out.

You may have a leak in the boost hoses between the turbo exit connection and the throttle body.

Yeah, that is pretty much the same thing (at least it describes it). It isn't that you HAVE an overboost condition, it's that the computer THINKS you have an overboost condition and thus cuts the fuel.
It literally takes no more than 3 minutes to check this. You could do it standing in the snow at a rest stop in the dark (but then you will drop the screws and spend half an hour looking for them before you step on one, snap it in half and then end up going to the dealer to spend $2.25 each for a stupid little piece of molded plastic.....)
Jim
93S4

By all means, check the ECU vacuum hose as Jim recommends; it is the most common hose (actually clamp) failure. However, when that hose comes loose, the wastegate simply opens normally at spring pressure. Normally, that should be around 8-10 psi, but I don't know to what pressure your TAP spring is set. BTW, this is an argument against wastegate springs. If your ECU decides boost pressure might damage your motor, it will cut off boost and only allow spring pressure, which it (Motronic) thinks is 8 psi. Having a higher "safe" boost pressure assumes you know better than the Audi engineers? Probably a small risk, but for what reward? Soapbox off.

Anyway, if the small hose blows off, the car behaves normally, it just doesn't make as much boost. This is not what you are describing. I think it is going to be either the turbo to crossover hose, or the crossover to intercooler hose (sometimes called the "Michelin Man" hose). Are you hearing any kind of "whooshing?" Check the ECU vacuum hose first, then the Michelin Man hose, then the turbo to crossover hose. That is in order of ease to check and actually the order of failure probability, too.

If the hoses are okay (check carefully), then Jason may be onto something with the 2.5 vs. 3.0 bar sensor. I'm not as familiar with TAP's upgrades. Good luck.

HTH,

Jim, I am hearing a whoosing sound. I thought this was normal because of the stiffer wastegate spring. I spoke with 1st owner who did the TAP upgrades and he mentioned to me the one thing he did not like about the upgrade was the noise from the wastegate spring poping. I wonder if I have more than one problem here.

I will check the hoses in the order you described.

I will also be happy when my Bentley CDROM arrives so I can get more familiar with this beast.

Thanks again for the advice.

Question: I originally mentioned the small hoseclamp failure under the black cover. Are you saying when that goes, it directs the wastegate to stay open continuously? When mine came off, as I stood on the gas, it built boost, then the fuel cut off around 4000rpm. Very repeatable and somewhat consistent. Am I understanding you that you believe when this hose comes off, you are limited to 8psi boost max? That is not what I felt while driving, it felt very violent, not just like the car was down on power all across the range. Perhaps I am misunderstanding you.
Question #2: Re: Whooshing: Ever since I upgraded to MTM 1+ software with 3bar sensor (I believe leaving me with your setup), I hear a sound that could be called whooshing, I would say it is more of a scraping, low pitched screeching noise that seems to come from near the wastegate (hard to tell when you're driving at full boost) at full throttle. Is this the shooshing you mean? Currently I am having a misfire at WOT, most noticable in 4th and 5th but there all the time, where it seems to hgesitate/stumble slightly at WOT. HOWEVER, if I back off just a bit, it smooths out and I seem to get more boost. I believe my hoses are OK, the 2 lower ones have been changed to MTM silicon, the upper (at the intake) needs to be changed (Samco unit in transit). Maybe I should check them again?
Jim

Jim,

Your symptoms of the hose clamp failure are virtually identical to mine.

The whoosing sound I hear is most noticable just as I back off on the throttle and push the clutch in to upshift. The heavier you are into the throttle before shifting, the more noticable the sound.

And is it just as you are LETTING UP on the throttle or as the boost really comes on, you hear the noise, THEN you get off the throttle?
Jim

>Are you saying when that goes, it directs the wastegate to stay open continuously?

No. The wastegate operates normally, but only to spring pressure. The ECU cuts the wastegate control when it doesn't get any manifold pressure input. So while driving, it builds pressure normally and then the wastegate opens at spring pressure (about 8 psi). So, the car behaves fine (no bucking or limp mode), it is just slower. In fact, I have removed that hose in order to test my spring pressure while doing the "Crank Down the Wastegate Spring Mod (tm)". Since the boost gauge will now reflect the spring rate. I have been so certain of this behavior that if somebody where to ask me what to do when their teenager wanted to drive their S4, I would tell them to pull this hose, because the kid would never know anything was wrong. I am not discounting your btdt, but I am as confused as you are about our different experiences. Although, you do have that whooshing...

I have suffered each of the hose failures:

ECU vacuum hose blowoff is described above.

Michelin Man hose failure put me into such a severe limp mode that I could barely move my car at all. 10 mph tops in the breakdown lane all of the way home.

Turbo to crossover hose failure gave me limp mode when I tried getting boost, but if I accelerated slowly, I could avoid limp mode and the car behaved normally.

If you want to keep this thread going, I have some thoughts as to why the car behaves differently, depending on what kind of hose failure exists.

I can't wait to hear how this turns out. Dammit man, the ECU hose takes 60 seconds to check; just go out and do it! ;-)

YMMV,

Interesting. You know, Jason mentioned that one of the other hoses IN THE SAME AREA as the ECU Vacuum hose causes the symptom you describe above. I wonder if you've never had what I have had (as well as quote a few others from the S-car list), Darin in fact tipped me off to it 2.5 years ago when it happened to me the day after I bought the car and if we are in fact talking about 2 DIFFERENT hoses that run right next to each other. I will have to remove the cover an look at the area in more detail....You'd remember it if it happened to you, it is scary, there you are giving it full throttle, loving the push in the back, when WHAM, around 4000rpms, you think you just ran over a curb or something. The car is still running and all, just the fuel totally cut off for a second.

I wonder why the limp mode is so severs for the big hoses, on the face of it you'd think (well, OK, I'd think) you'd just have a sort of lower compression NA 20v I-5

Yeah, Peter, get off your ass and check that thing. It's killing me too!

Humbly,
Jim K
93S4 (my leg is starting to hurt, I have a slight LIMP, hahahahahaha (Yes, I am reeeeeaaaally bored)

You guys are starting to scare me a bit :o
Just kidding!!!

I am going right now to get a new clamp and then take it for a good rip. I will let you know if it's fixed.

I wish all the repairs would be this cheap.

I replaced the clamp and then took it out for a little test drive. i wound her up to 6500rpm in 1-2-3 and no problems at all.

Thanks very much for your help everyone.