Rough and erratic idle - 2015 S4

[SteveYem]

I've been living with this rough, erratic, fluctuating idle in my 2015 S4 for probably over a year now and have come to no conclusions as to what is causing it. I've tried running with the stock tune and stock intake, stock tune and ECS intake, EPL Stage 1 tune and ECS intake, EPL Stage 1 and stock intake. It seems to do it to some degree regardless.

That being said, my engine-related modifications currently are:

EPL Stage 1 93 octane tune
ECS Luft-Technik intake
AWE Touring Exhaust w/ Resonated Downpipes

In the video below you can hear the exhaust note has a cyclical pattern, and when it sounds like it nearly cuts out the car shakes noticeably. I didn't capture it in this video but sometimes there are little "pops" when the exhaust note cycles down like that, also coincident with the shaking phenomenon.
Various times I have scanned the car for fault codes and have found nothing. I can barely see the tachometer fluctuating but I can feel and hear the engine speed fluctuating. All the while I have been noticing these symptoms, my gas mileage has been relatively worse and the car feels down on power.

I'm not pointing fingers, but I can confidently say that the car never did this when I was running the stock ECU software before the ECM update, or with the EPL Stage 1 tune that I flashed originally in January 2016 beforethey updated it with whatever tweak was necessary to protect the catalytic converters (just like the OEM ECM update). To complicate things, I also had the car in last year for the timing chain tensioner TSB and I am currently hearing the rattle sound on startup again, so whatever work they completed didn't seem to be a permanent fix.


So at this point, I'm just looking for ideas as to what could cause this phenomenon to occur in general. Some far-fetched and under-researched hypotheses I've had:
* a problem with the throttle valve that causes it to fluctuate open/closed slightly
* something broken loose in the exhaust system that is partially blocking the exhaust path, leading to these pulses, poor gas mileage and decrease power output
* a sign of catalytic converter failure

Any ideas are welcomed and appreciated!

https://youtu.be/WPYmqdIEsrA

[MSq5]

I do have a suggestion: Ross-Tech VCDS data logging. Log the parameters recommended by EPL they recommend for tune evaluation. Do this under conditions the replicate the problem. Post your log somewhere to a cloud based host with a link back here and let some of us look at it. Also send the log to EPL for their evaluation.

A second suggestion: Log onto your EPL account and check and see which map you are currently running and make sure it is up to date. If you took the car to the dealer for that timing chain tensioner issue, the dealer may have loaded their own current Audi ECU map. Could it be that you are running that instead of the current EPL Stage 1 map?

You may have already verified which map you have currently installed, but just in case, I mention this.

Finally, could this be something as simple as need to replace the air filter? Rough, erratic idle and increased fuel consumption are known to be associated with dirty/clogged air filter. It's easy to check. I'm not familiar with that particular intake or what filter it uses, though. According to their website it is an 8 ply cotton gauze filter (oiled) with 3" inlet, very similar to K&N or aFe filters used with Audi's stock air box. It's pretty hard to get such a filter dirty enough to impede flow unless it has well over 50,000 miles or has been seriously over-oiled. We don't have MAF sensors, so I doubt oil could cause the erratic idle unless, it is so thick that it is impeding air flow at idle.

[SteveYem]

I do have a suggestion: Ross-Tech VCDS data logging. Log the parameters recommended by EPL they recommend for tune evaluation. Do this under conditions the replicate the problem. Post your log somewhere to a cloud based host with a link back here and let some of us look at it. Also send the log to EPC for their evaluation.

A second suggestion: Log onto your EPL account and check and see which map you are currently running and make sure it is up to date. If you took the car to the dealer for that timing chain tensioner issue, the dealer may have loaded their own current Audi ECU map. Could it be that you are running that instead of the current EPL Stage 1 map?

You may have already verified which map you have currently installed, but just in case, I mention this.

Finally, could this be something as simple as need to replace the air filter? Rough, erratic idle and increased fuel consumption are known to be associated with dirty/clogged air filter. It's easy to check. I'm not familiar with that particular intake or what filter it uses, though. According to their website it is an 8 ply cotton gauze filter (oiled) with 3" inlet, very similar to K&N or aFe filters used with Audi's stock air box. It's pretty hard to get such a filter dirty enough to impede flow unless it has well over 50,000 miles or has been seriously over-oiled. We don't have MAF sensors, so I doubt oil could cause the erratic idle unless, it is so thick that it is impeding air flow at idle.


Thanks for your reply! If I get the opportunity I will do some VCDS data logging this weekend and report back. Are there specific parameters that I need to log?
A few months ago when the issue was getting more noticeable (or at least more on my nerves) I also suspected a dirty air filter could be the culprit. At that time I was using the oiled filter that came with the intake from ECS. In an effort to eliminate the variable of the possibility that I had over-oiled the filter during its previous cleaning, I have since swapped to an AFE dry filter with equivalent dimensions and it seemed to make no difference. I inspected the AFE filter a few days ago and did not notice any appreciable dirt or debris accumulated on the outside.

According to the EPL Flash Loader, I am running the Audi B8.5 Stage 1 - 8K5907551F - 93 - 5/8/18 map. When I took the car in for the tensioner TSB (sometime in autumn 2017 IIRC), I flashed back to stock before I took it in, then flashed back to EPL Stage 1 a few weeks after the work was done. Subsequently I had flashed to and from stock a couple of times, iterating with stock intake and ECS intake, to see if any combination made the problem go away. So far, none of those combinations seemed to solve the issue.

I will say that when I first got my car back from the dealer after the tensioner TSB, it seemed to drive more smoothly and with less effort - like the engine was pulling me along as opposed to now where I feel like I am pushing it. Even clutch engagements were smoother. After a few weeks it was back to behaving the way I described in the original post. During that few weeks I also had flashed back to EPL Stage 1, which is why I subsequently flashed back to stock to see if I could narrow down the problem to the Stage 1 tune, but that didn't seem to be the case.

[SteveYem]

Finally had a chance to run VCDS and collect some data. I did not know which parameters I should be monitoring so I decided on Ignition Timing and Throttle Position, since I thought those might be relevant players in the phenomenon shown in my video in the original post.

This first log is me driving around at various throttle applications, coming to a couple stops. When I came to those stops, the engine was stumbling about just like in the video and I noticed that the ignition timing seemed to be bouncing all around:
https://www.dropbox.com/s/hr0l9ngff5ruvb6/LOG-33-0E-11-0D-77.CSV?dl=0


And this second log was sitting stationary with the car running, transmission in neutral. I forgot to log vehicle speed but it was Zero, and you can see that throttle position remains at roughly 11.8% for the duration which I presume is normal for when the car is idling. Again, the ignition timing appears to be jumping all around, and again the engine was stumbling/cycling/vibrating while this data was being recorded.
https://www.dropbox.com/s/bk4b0qeqd75os63/LOG-33-0E-11-70-12.CSV?dl=0


Food for thought - I had this issue prior to changing out my spark plugs earlier this year. It didn't seem to change with the new plugs. I gapped the new plugs to 0.026" per EPL recommendation for the Stage 1 tune. These data logs were taken with EPL Stage 1 tune and ECS Luft-Technik intake system with AFE dry filter.

[Oloung1]

this is random but how many hours or days did you run your stock/swaps in your first post? don't these ecus take a bit of time and mileage to adapt? i doubt it would be related to the tune or intake but just for science sake, i am curious of the adaptation period. from reading your threads, i know you are conscientious about your mods. i can't help much with logs, they are greek to me.

[SteveYem]

this is random but how many hours or days did you run your stock/swaps in your first post? don't these ecus take a bit of time and mileage to adapt? i doubt it would be related to the tune or intake but just for science sake, i am curious of the adaptation period. from reading your threads, i know you are conscientious about your mods. i can't help much with logs, they are greek to me.

Good question and I should have included in my original post. I went at least ~1 week (probably 200-250 miles) with each setup for exactly that reason - I wanted to make sure it had enough time to adapt.

[Ford Prefect]

Good question and I should have included in my original post. I went at least ~1 week (probably 200-250 miles) with each setup for exactly that reason - I wanted to make sure it had enough time to adapt.


These would be better

Group 15 - Field 0 Vehicle speed
Group 25 - Field 0 Engine speed
Group 216 - Field 0 IGA_AD_1_KNK[0]
Group 222 - Field 0 Ignition angle; actual
Group 233 - Field 0 Lambda probes actual; bank1
Group 345 - Field 0 Air mass
Group 352 - Field 0 Intake manifold pressure
Group 556 - Field 0 Intake air temperature
Group 623 - Field 0 Charge air pressure specified value
Group 625 - Field 0 RFP_AV

And you can add 3-4 gals of E85 with a fill up of 93 as well.

Hey Steve, I am EPL stage 2 and have timing pull across all cylinders. Over in the EPL thread Chris told me to log the above values, might be a good general place to start. That sound is definitely strange, it sounds like one cylinder isn't firing every X number of times. It seems oddly consistent.

Oh, and when you log, make sure you group them. After you select the parameters, up to 10 I think (for me in a B8 anyway), click the Turbo! button at the top (whatever that does) and then check the 'Group' check box just to the left. Grouping will give every logged value the same time stamp, otherwise everything is logged when it feels like it instead of at the same time.

[SteveYem]

Hey Steve, I am EPL stage 2 and have timing pull across all cylinders. Over in the EPL thread Chris told me to log the above values, might be a good general place to start. That sound is definitely strange, it sounds like one cylinder isn't firing every X number of times. It seems oddly consistent.

Oh, and when you log, make sure you group them. After you select the parameters, up to 10 I think (for me in a B8 anyway), click the Turbo! button at the top (whatever that does) and then check the 'Group' check box just to the left. Grouping will give every logged value the same time stamp, otherwise everything is logged when it feels like it instead of at the same time.


Thank you, I will give that a try. I saw the 'Turbo!' button but did not know what it did. As far as I can tell, VCDS would only allow me to select 4 parameters at once - at least, there were only 4 available slots in that window of the VCDS software. Maybe there is an option to expand the list of available slots? I'll take another look this weekend and report back.

[SteveYem]

OK, new data log up for review, logging the parameters suggested by Chris @ EPL by way of @FordPrefect:

https://www.dropbox.com/s/a7j26dxwhj3ck5l/LOG-01-IDE00021_%269.CSV?dl=0

[SGR]

Have you considered a vacuum leak?


Sent from my iPhone using Audizine (http://r.tapatalk.com/byo?rid=87676)

[SGR]

Side note — I’m quite certain it’s normal for the timing to jump around a bit when you aren’t doing a WOT pull.


Sent from my iPhone using Audizine (http://r.tapatalk.com/byo?rid=87676)

[Chris@EPL]

You are also not running the most up to date tune. You flash the Stage 1 file in March and then yesterday flashed the stock file back on. The Stage 1 93 file was updated in May. But I know you have mentioned in the past about some exhaust downpipe issues. This sounds more like a vacuum issue. But flashing the update can not hurt. If it was a tune issue it would disappear when you flash to stock and you have said it is still present when you are on the stock file.

[SteveYem]

You are also not running the most up to date tune. You flash the Stage 1 file in March and then yesterday flashed the stock file back on. The Stage 1 93 file was updated in May. But I know you have mentioned in the past about some exhaust downpipe issues. This sounds more like a vacuum issue. But flashing the update can not hurt. If it was a tune issue it would disappear when you flash to stock and you have said it is still present when you are on the stock file.


Thanks for chiming in as always, Chris. That's good to know about the tune.
A couple days ago I flashed back to stock and the issue is still present. I'll drive around for another couple days just to be sure, but as of this morning the same issue exists. Later this week I'll swap the stock intake back in and see if that changes anything. On a related note (maybe), I've been hearing the timing chain noise again recently when I start the car. I already had the chain tensioners replaced per the TSB but I guess it didn't take. Is it possible that the symptoms I'm reporting are related to a timing issue? Does my logged data support that theory?

Once I get the stock intake back in I will be taking the car back to the dealer so they can try again. My warranty is almost up so I'm due for my last visit anyway. But in the meantime, I'd like to learn whether this could be caused by a timing chain issue so that I can be armed with more knowledge in case the service department wants to deny that the issue exists.

[Chris@EPL]

The timing numbers in the log are fine as it changes quickly based on throttle input and that is normal.

[SteveYem]

The timing numbers in the log are fine as it changes quickly based on throttle input and that is normal.

OK, thanks for confirming. If you don't mind educating me a bit, what leads you to say this could be a vacuum leak? And do you have any suggestions on where to check? I don't know much about this but would like to point the service department in the right direction...

[denako]

Thanks for chiming in as always, Chris. That's good to know about the tune.
A couple days ago I flashed back to stock and the issue is still present. I'll drive around for another couple days just to be sure, but as of this morning the same issue exists. Later this week I'll swap the stock intake back in and see if that changes anything. On a related note (maybe), I've been hearing the timing chain noise again recently when I start the car. I already had the chain tensioners replaced per the TSB but I guess it didn't take. Is it possible that the symptoms I'm reporting are related to a timing issue? Does my logged data support that theory?

Once I get the stock intake back in I will be taking the car back to the dealer so they can try again. My warranty is almost up so I'm due for my last visit anyway. But in the meantime, I'd like to learn whether this could be caused by a timing chain issue so that I can be armed with more knowledge in case the service department wants to deny that the issue exists.

FWIW, I had a similar issue like yours that I talked to Chris @ EPL about. In high heat, high humidity days where I'm driving in heavy traffic (or other cases where the engine is producing a lot of heat like WOT runs), I would have an idle surge. You can hear it from outside the car without a doubt but I also had the surge on my tach. It would hop from idle to 1200 rpm, come back down and repeat itself. Same mods and car basically.. 2011 6MT with EPL Stage 1 + Intake and Exhaust. I reflashed to the May 2018 revision and have since had the issue. It's been about a week for that matter but I also just did a 500 mile round trip to WI this past weekend with no issues.

I'm kind of confused whether you've flashed the May revision yet or not, but if not.. I would recommend it as your next step. Doesn't hurt.

[SteveYem]

FWIW, I had a similar issue like yours that I talked to Chris @ EPL about. In high heat, high humidity days where I'm driving in heavy traffic (or other cases where the engine is producing a lot of heat like WOT runs), I would have an idle surge. You can hear it from outside the car without a doubt but I also had the surge on my tach. It would hop from idle to 1200 rpm, come back down and repeat itself. Same mods and car basically.. 2011 6MT with EPL Stage 1 + Intake and Exhaust. I reflashed to the May 2018 revision and have since had the issue. It's been about a week for that matter but I also just did a 500 mile round trip to WI this past weekend with no issues.

I'm kind of confused whether you've flashed the May revision yet or not, but if not.. I would recommend it as your next step. Doesn't hurt.

I was apparently not running the latest version of the Stage 1 software and will certainly be flashing to it after my next service visit, but in the meantime I've flashed back to stock and am still having the issue so I do not believe it is tied to the tune.

[3g_bishi]

I would try to clean out the throttle body and reset the adaption or idle in vcds


Sent from my iPhone using Audizine (http://r.tapatalk.com/byo?rid=87676)

[SteveYem]

I would try to clean out the throttle body and reset the adaption or idle in vcds


Sent from my iPhone using Audizine (http://r.tapatalk.com/byo?rid=87676)


I tried that a couple months ago (when these symptoms seemed to intensify) and it did not make a difference, unfortunately.
I have an appointment to take the car in to Audi on Monday. I wrote in the service request that I am hearing the timing chain rattle again at startup, even though they replaced the tensioners per the TSB last December. I am also going to show them videos I have taken of both the timing chain rattle and the erratic idle, in case they can't replicate them readily. I had another thought, though - could these symptoms be caused by excessive carbon buildup on the intake ports / valves?

[cardiffGIANT67]

Did this issue get resolved? Just curious as I think i'm experiencing a similar issue in my '09 S5 4.2L, no mods yet. I wish I could watch your video but it's not popping up on my end for some reason. But I'm having the same sporadic idle issue almost exactly how you describe. You can't really see much of a change in the tach but you can definitely hear it and slightly feel it while sitting in the car. It seems to only happen at idle and is more noticeable when in gear. Seems to run very good under power, I don't really notice any loss when going through the gears. I've noticed this problem start to occur about 3 months ago.
I had it in the shop about 2 weeks ago and they actually kept it for 4 days trying to diagnose it. No CELs, no long term codes showed up on their end. (sorry I didn't get a scan read out from them and I don't have vagcom yet) I had them do a carbon clean which definitely made it feel a lot smoother during normal driving conditions but the idle issue is still there.
Just curious what you found out before I start throwing parts at it.

[SteveYem]

No resolution yet. I have an Audi tech friend who is hopefully coming over within the next couple weeks to take a look at it with me. He said maybe it's a crankcase pressure issue but that's above my head. I will definitely report back with whatever we find.

[Toine888]

Hey steveyem keen to hear if this issue was resolved and if it was a PCV issue on the crankcase? Think I may be having a similar issue in my B8.5 S4. My only symptoms are a rough idle and loss of power. No cell lights at this stage.
Thanks!

[SteveYem]

Hey steveyem keen to hear if this issue was resolved and if it was a PCV issue on the crankcase? Think I may be having a similar issue in my B8.5 S4. My only symptoms are a rough idle and loss of power. No cell lights at this stage.
Thanks!

No, unfortunately the Audi dealer reported that the car was “operating within normal parameters” and my warranty has since expired, yet the issue persists. I’m taking the car to an independent shop later this week to see if they can make any determination.

[Toine888]

No, unfortunately the Audi dealer reported that the car was “operating within normal parameters” and my warranty has since expired, yet the issue persists. I’m taking the car to an independent shop later this week to see if they can make any determination.

Ok let me know how it going - I’m unsure what to do as been quoted $1k to diagnose and replace PCV, however I don’t even have any CELL so not sure how serious it is... plus dont really have $1k to spend now but jus worried the tune I have it maybe a bit lean and I don’t want downstream issues...


Sent from my iPhone using Tapatalk

[vitopat]

I've been living with this rough, erratic, fluctuating idle in my 2015 S4 for probably over a year now and have come to no conclusions as to what is causing it. I've tried running with the stock tune and stock intake, stock tune and ECS intake, EPL Stage 1 tune and ECS intake, EPL Stage 1 and stock intake. It seems to do it to some degree regardless.

That being said, my engine-related modifications currently are:

EPL Stage 1 93 octane tune
ECS Luft-Technik intake
AWE Touring Exhaust w/ Resonated Downpipes

In the video below you can hear the exhaust note has a cyclical pattern, and when it sounds like it nearly cuts out the car shakes noticeably. I didn't capture it in this video but sometimes there are little "pops" when the exhaust note cycles down like that, also coincident with the shaking phenomenon.
Various times I have scanned the car for fault codes and have found nothing. I can barely see the tachometer fluctuating but I can feel and hear the engine speed fluctuating. All the while I have been noticing these symptoms, my gas mileage has been relatively worse and the car feels down on power.

I'm not pointing fingers, but I can confidently say that the car never did this when I was running the stock ECU software before the ECM update, or with the EPL Stage 1 tune that I flashed originally in January 2016 beforethey updated it with whatever tweak was necessary to protect the catalytic converters (just like the OEM ECM update). To complicate things, I also had the car in last year for the timing chain tensioner TSB and I am currently hearing the rattle sound on startup again, so whatever work they completed didn't seem to be a permanent fix.


So at this point, I'm just looking for ideas as to what could cause this phenomenon to occur in general. Some far-fetched and under-researched hypotheses I've had:
* a problem with the throttle valve that causes it to fluctuate open/closed slightly
* something broken loose in the exhaust system that is partially blocking the exhaust path, leading to these pulses, poor gas mileage and decrease power output
* a sign of catalytic converter failure

Any ideas are welcomed and appreciated!

https://youtu.be/WPYmqdIEsrA

I'm having a similar issue, after doing some research on this i think it might be the LPFP. I heard the RS7 LPFP is a plug/play pump for the S4. Down the road i will try changing out the pump and see if that fixes the problem.

[hjaaamjb6]

FYI I had the same issue and dealt with it for 2 years. No codes. It was the PCV valve. Don't always trust Audi's diagnostics. If they don't see a code or if it passes their pressure test they will be always say no. I'm not trying to say go spend $1k to do it because of my word, but if you're mechanically inclined and do it yourself worst case it doesn't fix it you spent about $200 for everything and have a fresh PCV which is always good as it's prone to failure anyways. But with that being said my money is on the PCV regardless of what the dealer says.

[SteveYem]

FYI I had the same issue and dealt with it for 2 years. No codes. It was the PCV valve. Don't always trust Audi's diagnostics. If they don't see a code or if it passes their pressure test they will be always say no. I'm not trying to say go spend $1k to do it because of my word, but if you're mechanically inclined and do it yourself worst case it doesn't fix it you spent about $200 for everything and have a fresh PCV which is always good as it's prone to failure anyways. But with that being said my money is on the PCV regardless of what the dealer says.

I saw your post in the "Invisible Coolant Loss" thread but was not sure whether you had seen any resolution on the issue. I am planning to take my car in next week for PCV replacement, T-stat replacement and intake valve carbon cleaning. A cool $1450 but if it solves the problem and gets the car running well again, I'll feel it's money well spent. I'm going to post over in that thread as well..

[jygesq]

I saw your post in the "Invisible Coolant Loss" thread but was not sure whether you had seen any resolution on the issue. I am planning to take my car in next week for PCV replacement, T-stat replacement and intake valve carbon cleaning. A cool $1450 but if it solves the problem and gets the car running well again, I'll feel it's money well spent. I'm going to post over in that thread as well..

how many miles on your car?

[SteveYem]

how many miles on your car?

Currently 56000

[jsh139]

Where are you taking it, Steve? Performance Auto in Malvern? Been trying to find a solid independent shop in the area. I've tried a few.

[SteveYem]

Where are you taking it, Steve? Performance Auto in Malvern? Been trying to find a solid independent shop in the area. I've tried a few.

I am planning to take it to The Porsche Specialists in Broomall. A friend of mine (former Audi tech) is one of the mechanics there which is how I found out about the place. I'm hoping to get it in there end of next week so I will let you know how it goes. I did stop in at Performance Automotive in Malvern last year to discuss tire mounting and alignment but never ended up following through with them, despite their being the closest higher-end indy shop to my location. I couldn't really explain why....but I do want to get my alignment redone and might be taking it to them. They really seemed to know their stuff.

[jsh139]

I am planning to take it to The Porsche Specialists in Broomall. A friend of mine (former Audi tech) is one of the mechanics there which is how I found out about the place. I'm hoping to get it in there end of next week so I will let you know how it goes. I did stop in at Performance Automotive in Malvern last year to discuss tire mounting and alignment but never ended up following through with them, despite their being the closest higher-end indy shop to my location. I couldn't really explain why....but I do want to get my alignment redone and might be taking it to them. They really seemed to know their stuff.

Cool. Broomall is a hike, but if they fix your issues, it'll be worth it. I've taken my car to Performance a couple times. Nice guys. Labor rate is a little high (I think they work on Porsches more, so there's a Porsche tax), but they seemed to be good at the normal maintenance items. Was curious how they did on something more involved like the therm/PCV/carbon cleaning if you were taking your car there. But, I'll still be curious to hear how this other shop does.

[SteveYem]

Cool. Broomall is a hike, but if they fix your issues, it'll be worth it. I've taken my car to Performance a couple times. Nice guys. Labor rate is a little high (I think they work on Porsches more, so there's a Porsche tax), but they seemed to be good at the normal maintenance items. Was curious how they did on something more involved like the therm/PCV/carbon cleaning if you were taking your car there. But, I'll still be curious to hear how this other shop does.

Yep, definitely a hike and extra inconvenient because they will need the car for a full day to do the work; however, if they have availability I'm going to drop off the car on my way to the airport for a trip next Wednesday, Uber to/from the airport and pick it up on my way back Saturday night. If they aren't able to fit it in during that time frame I may look elsewhere.

I also got the impression that Performance Auto was a bit high-priced. They quoted something like $220 for an alignment including ride height adjustment to my specifications. Not terrible, but seemed high. I was expecting more like $180 although I don't have a great basis for that. On the other hand, I just paid another local indy shop (not really an aftermarket / performance shop) $100 last week to do an alignment but they were only willing/able to align to OEM specs which left me with more rear toe angle than I really care for, so I'm going to have to bit the bullet and take it to a performance oriented indy shop to get it done to my liking. Pay to play, get what you pay for, etc etc.

[jsh139]

Yep, definitely a hike and extra inconvenient because they will need the car for a full day to do the work; however, if they have availability I'm going to drop off the car on my way to the airport for a trip next Wednesday, Uber to/from the airport and pick it up on my way back Saturday night. If they aren't able to fit it in during that time frame I may look elsewhere.

I also got the impression that Performance Auto was a bit high-priced. They quoted something like $220 for an alignment including ride height adjustment to my specifications. Not terrible, but seemed high. I was expecting more like $180 although I don't have a great basis for that. On the other hand, I just paid another local indy shop (not really an aftermarket / performance shop) $100 last week to do an alignment but they were only willing/able to align to OEM specs which left me with more rear toe angle than I really care for, so I'm going to have to bit the bullet and take it to a performance oriented indy shop to get it done to my liking. Pay to play, get what you pay for, etc etc.

I've had really great results with Leading Edge Autosport in West Chester. They were the ones that correctly diagnosed my clutch issue. I would take my car there again. The only problem is they will not allow you to wait for any service. It's drop-off only, which is a little inconvenient since that requires a rental car for me. So, I've only been taking my car there for things that take longer than a few hours. But, the owner knows his stuff and his personal car is a B8.5 S4, so that is comforting.

[MikeB8.5]

Posted this response in an older thread as I wasnt paying attention to the dates of the last reply. Going to share again as I'd really like to figure out what the hell is causing this.


Hey all,

Just thought I'd share my experience with this issue as well since I've been searching endlessly for a solution to it before I have to take the car in to either Audi or a reputable indy shop.

So I have a 2013 S4 Premium 6MT with 154xxx KM on the clock. I am the second owner and purchased it with around 144xxx KM a little over a year ago. It's all stock from what I can tell, other than the intake and I threw a set of H&R super sport springs in (which wouldn't affect anything).

Last fall, shortly after I purchased the vehicle it threw codes for SAI flow bank 1 and 2. Around the same time it started to develop a strange idle hunt, I assumed it was related to the SAI system. After some reading on here I decided to tackle cleaning the carbon on the Intake side myself, as well as changing the PCV since someone mentioned the idle might be related to the PCV being worn out. After cleaning and reassembly the idle hunt was still present. So onto the next step, getting the SAI system cleaned. Just last week I took it in to Audi to have the SAI cleaned on both banks, hoping that this would remedy the idle hunting issue. Took them less than a full day to clean it and have my car back to me error free on the SAI side of things. Unfortunately the idle issue is still present, if not worse now.

A few things to note : During the time frame I had a few high idle codes as well, which have not returned since. The car also has some chain rattle on start ups and I'm unsure if the chains and timing system are related to the idle surge/hunt. I have noticed poor fuel mileage, possible mystery coolant loss and the idle surge only seems to occur after the car is fairly hot. highway driving seems to calm it down and stop and go city traffic makes it notably worse. I've also noticed the throttle will bog a bit if you step try to give it some revs in neutral or in first with the clutch depressed. It makes acceleration from first difficult at times since it bogs a bit. Otherwise the car drives fine and pulls hard when you want it to.

Also wanted to point out, from my experience that the OP's issue isn't related to his tune and mods. Maybe it was just a matter of timing that it happened.

This is pretty frustrating after throwing money and time into cleaning the carbon and replacing parts and still not resolving the issue. I've searched a few threads on here and no one seems to have a conclusion to what it may be.

[SteveYem]

I started sharing my updates on a different thread but wanted to link it here (see below) in case anyone wants to follow along. If I ever get the issue resolved, I will update this thread with a summary of the work done and the root cause if identified.

https://www.audizine.com/forum/showthread.php/722255-Help-Idle-hunting-surging-with-video

[Silver Streakin]

another shop in the area is Dougherty Automotive.

I turn my own wrenches, but they bailed me out of a wheel bearing job when a lug snapped. Nice guys. Loaner cars. They're also the place the local guys use for DE prep and sign off.

[jsh139]

I started sharing my updates on a different thread but wanted to link it here (see below) in case anyone wants to follow along. If I ever get the issue resolved, I will update this thread with a summary of the work done and the root cause if identified.

https://www.audizine.com/forum/showthread.php/722255-Help-Idle-hunting-surging-with-video

I'd suggest calling or emailing Mark at Leading Edge Autosport in West Chester and just run it by him. He's really knowledgeable with our cars (he owns a B8.5). I know that you don't want to keep throwing money at the car, but maybe something will click and he'll know what it is offhand. Worth a shot.