I thought my Audi was idling rough and also have this jolting under exceleration. It is most noticeable in 4th gear at about 2000 RPM until it hits 3500RPM then is gone. so i decided to put some better plugs in. I did notice the Idle was now smother and some smoother excelleration but still have not worked out the issue of the jumping. Its like the car studders 5 or 6 times before it finally decides to get up and slam the power down. Any Ideas anybody?

Take out the iridium plugs and make sure you are using a fresh set of Bosch Platinums (P5DFOR - may be wrong code, I can't remember it - it lists the correct plug in your manual). As far as I know, these are the only plugs that work well/correctly in this car. I don't know anyone who uses anything else.

Check your plugboots to see if they are in OK condition.

Check your MAF to see if it's gunked up. Especially if you have an oiled K+N filter.

Keep driving it, this seems to sometimes be an early symptom of either a coilpack or a PSO device going bad. It will get worse with time if it's one of these. Although genereally you will have the hesitation at WOT throghout the rev range, not just 2000-3500.

Otherwise, I am not sure. You know, flooring a stock Ur-S4/6 at 2000 RPM's in 4th doesn't give a strong result. I realize the torque theoretically is all there from 1900rpm's, but my butt-dyno sure doesn't notice it until that big slug of power at about 3500 rpms. Maybe you're just feeling a bit of lugging???

Jim K
93S4

I noticed the plugboots ( the rubber tube from the coil pack to the plug is starting to look alitle burnt or brown at the bottom and there is some cracking at the bottom also. i have been trying to find an aftermarket one with no luck.
The dealer wants 79 per boot :( If you know of an aftermarket replacement please tell me. I understand the 2000 rpm thing but this is the best way to feel what is happening. Its not something i do on a regular basis. I have done a fair bit or research on the plugs and thought they would be the best choice because of the lower voltage requirement of the plug thus making idle more stable plus they do not cause as much heat therefore keeping the oil temp down as well. I did have the factory replacement plugs in when this started to happen, this is y I changed them (Twice now) Trying different brands. so i believe you are right that the problem resides in one of the latter. I did remove the MAF and it looks ok. i am now replacing the bypass valve with the forge replacement but don't know if the replacement is the correct one because it lists for the 1.8 A4. my understanding from the sales guy from stratmosphere is that i need the 007p but he did not mention the adapter which will also be needed which i found out talking to another salesman from another company here in Canada. I am also replaceing all the Hoses with the Samco replacements. To Turbo, From Intercooler and such. Hoping I catch the problem along the way with upgrade that are needed anyway.

I'm not sure what you mean by a PSO Device Going Bad though. I have an appointment on the 7th to have the system tested, ECU and Pressure test the turbo system hoses and such so I'm hoping this might reveal something also.

O yes i do have a K&N oil filter but the problem started before i installed it, it was one of the things i am trying to resolve the issue

Thanks Again

Plugboots: Try either www.thepartsbin.com or www.thepartsconnection.com. I got them for I believe $18 apiece last year. Same exact part as the dealer has.
Sparkplugs: See above. Around $12 each.
PSO - Power Stage output device - it contols when each sparkplug gets juice. There are 2 on this car. They are both on the firewall. They cost a lot, around $350 each. Same symptoms as a coil going bad. When it gets bad enough that the engine is missing at idle, it's easy to figure out what's bad just by interchanging the components on the car as it sits.
Filter: You may want to swap the original one back in for the testing. Someone will blame it on the K+N, just switch it back now and save the hassle.
Good luck
Jim

Or do you think i can dismantle and clean it up ?

Sorry, I don't know anything about that part. But look around to see how cheap it is to replace it at thepartsbin.com and TPC.com etc. Then decide, I guess.
Sorry,
Jim
93S4

I looked on thepartsbin but didn't find the part. not sure about the golf site though :).
Dealer wants about 310cdn and 2 hour to put the part in. So going to have my KY recall done at the same time.
The dealer new about this recall and didn't even call me back. so about 2 months later I made an appointment and went yesterday at about 8am to drop off the car and they didn't even have the parts in stock :( The never ordered them. and this recall is what i think very: like do it now) well once I found out what the recal was that is.

so anyway haveing the censor and that done tomorrow morning. mabe they will have the part this time.

I meant www.ThePartsConnection.com, didn't mean to route you to golf...Well, that seems cheap enough, what's 310 cdn, about US$2, right? Just kidding.
Let us know if the Throttle Position Sensor part did the trick.
Jim

Well had the Throttle Position Sencor replaced today and it's now running smooth :) total cost of 680cdn or 421US they also regapped the Iridium plugs to the correct gap to my car. Denso pre-gapps them to .044 and the S4 gap is .032 (I think) I sent an email to Denso and they suggested to change the gap to the S4 gap and the idle has now smothed out quite a bit. These are nice plugs and seem to work fairly well on the s4. I ran the car hard for about 2 hours today and all was well, so plugs and TPS working great. Thanks for folowing up.