Slight bucking/surging at a VERY small amount of throttle (20 inHG), any ideas?

[Blue AWD]

When I barely press the gas, just to keep speed, I am getting a really small buck, on and off. Could it be my divertor valves? They are somewhat old. No codes or anything. Car pulls pretty strong but it has a tendency to break in and out at WOT.

Car holds boost fine and sometimes acts perfectly normal. Any ideas are appreciated. Thanks.

[BITRBO]

Well, all I can say is at least you're not alone... I've had this problem since I've owned the car, and it's been driving me NUTS ever since. Here's one of my many desperation threads:

http://www.audizine.com/forum/showthread.php?t=139876

The only change to my original symptoms is: It really does this in any gear regardless of speed; but I must be in ~10in HG or less of VAC (flat road on stead throttle or in cruise). In fact, it's more noticible now in 1st or 2nd gear. Also, the warmer the ambient temp the worst and more frequent it becomes.

I even took a few quick video clips with my digital camera (I know, I know. They kinda suck, but you get the point):

http://www.youtube.com/watch?v=5DG8827TB8o

http://www.youtube.com/watch?v=eT5cx...eature=related

Anyways, my next step is to get VAG-COM and/or APR's ECU-Xplorer to try an diagnose the issue. I never get any CEL's or silent codes, but I figure if I run a bunch of logs I'm bound to find the problem (*fingers crossed*)...

GL

[momento1]

i had this same problem at crusing speeds also after i went stage 3...

it fustrated me so much...
however i did fix it and it was quite simple..

When i had the AWE MAF installed, my mechanic didnt put in the flow straightner (which goes just before the MAF).
I got a hold of one from AWE and hay presto, the bucking stopped.
im told its simply the turbulence felt by the maf sensor without the straightner

hope this helps guys

[Blue AWD]

Yea my boost doesnt flutter its just something I can feel.

[j_korteS4]

I had the same problem for almost two years, since I bought mine. The problem has completely stopped since I replaced the spark plugs with OEM NGK's about two weeks ago. Hasn't bucked once since!!!

[b5s4blk]

Yea my boost doesnt flutter its just something I can feel.

i know exactly what you are talking about. my car does the same thing with no boost flutter. to me it feels like for lack of a better word the "slack" is being taken out of the drive shaft from when it goes from low torque to you pressing on the gas and adding torque to the drive shaft. and yes i know obviously the drive shaft has some torque on it when the gas is not being applied. thats just what it feels like to me. maybe bad/worn out yolks. Or maybe a bad drive shaft bearing ?

[s4twin]

i had this same problem at crusing speeds also after i went stage 3...

it fustrated me so much...
however i did fix it and it was quite simple..

When i had the AWE MAF installed, my mechanic didnt put in the flow straightner (which goes just before the MAF).
I got a hold of one from AWE and hay presto, the bucking stopped.
im told its simply the turbulence felt by the maf sensor without the straightner

hope this helps guys

been awe stg 3 for the past 8 months, started to get this bucking syndrome for the last month and half. hopefully just needs some plugs.

[BITRBO]

yeah, I've already swapped out my MAF with a new one and it still does it... both had the flow straightener too. I also switched to Denso's and those seemed to help a little, but I'm not really sure anymore.

Latley I've noticed that my exhaust smells a little funny, but I can't describe how. Just "funny". Like the CATs are eff'ed or something. My gas mileage has been getting worse too (~240-260 mpt city). I have a feeling (more like "hoping") it's either my EGT's and/or O2 sensors... I'll post my findings soon enough.

[b5s4blk]

after searching the forum i found this thread. http://www.audizine.com/forum/showthread.php?t=184243 has some good pics of the bearing i was talking about, in the audiworld links by jakecro

[Evilevo]

I have been having this problem also. I replaced the plugs and that didnt help. My front O2 sensors are bad and i am replacing them on tuesday. I was told by AWE that since mine is an early stg 3 kit that the Injectors need to be rotated to have the clips face towards the fenders. I will try that also and let you guys know happens

[Evilevo]

I replaced one of my o2s, it seemed to help for abit, but than it got worse. Doing the other 02 soon.

[BITRBO]

hopefully my new laptop will be in by the weekend, so I can download VAG and run some logs...

[Evilevo]

just ran logs. Seemed that my car was misfiring when it was bucking.

[dak360rt]

My car is doing it too, but mine seems worse than what yours sounds. When i get on the throttle close to WOT around 4000 rpm it will pull for a second then its like no boost, then it will pull again, and then it will feel like no boost again, i dont have a gauge yet to see if boost is actually being cut, but my mechanic told me that i have bad EGT sensors.

Marty

[highPSI-S4]

i too have had these kind of problems and i'am currently logging it now.
for the most part di we want to associate the bucking with maybe hesitation?
This kind of problem can be multiply things from a spark plug to a coilpack, ICM,o2 sensor, EGT. I had a primary o2 sensor go bad car was bucking and misfiring, i also got codes for egt and secondary o2's. Since i have replaced the primary o2 and still alittle bucking but no codes for the other o2's or EGT it just says misfire cylinder 2 and multiply misfire code. Just do a process of elimanation. my car also starting bucking when my MAF went wacky.

[BITRBO]

so I don't thread jack the OP anymore, I've got some updates for those interest in my plight:

http://www.audizine.com/forum/showth...99#post2687299

[DuWerk]

Yeah,

I have been dealing with this issue since last October when I finally put on my AWE fueling kit. ( I had the K04's on there already from a trans job I did prior) I have a nogaro blue 01 S4 avant with blue alcantara. It has been K04'ed with DP's etc. I thought I had a leak in the intake system somewhere but I can't find it.
I also get bucking, hesitation at slight throttle when I am in more than 10HG vacuum. ( 10-20 ) It is noticeably worse in warmer weather. It seems better when I reset the CEL light with the VAG com. The codes i routinely get are fuel trim to rich and fuel trim to lean on bank 1 and bank 2. They come back every time. I can't inspect the car, it never gets its readiness codes.
I changed the plugs, no better. I swapped the MAF, Ignition stages, replaced the front two O2 sensors with new OEM (with plug etc) Bosch units. I swapped the throttle body, swapped a buddy's ECU in with no tuning..... All stays the same always. I swapped DV's, replaced the Coolant Temp sensor still no better. I am def gonna try the air Grid straightener on the MAF that was mentioned earlier up in this thread. I have not once gotten any misfire codes?????? How weird is that. I also played all around with the injector orientation and that didn't change a thing either. The thing with my car is it almost too violent to drive sometimes when it is hotter outside. And the gas mileage is like 16mpg right now. I can't even get 200 miles to a tank, so it just sits there while my brembo 14 inch brakes get rusty and are now shaking and pulsing. Damn it!!
The only thing I still have to do is to replace the driver side lower intercooler pipe. When I smoked out the intake to check for leaks, I saw some smoke come from the weld where the mounting bracket is that holds it to the upper part of the oil pan. That just doesn't seem like a big enough leak to cause this problem. But I do have the pipe and I am going to change it.



Has anyone else made any headway on their issues?

Just for side fun, I had to replace the Alternator the other day too!! I just want to drive this car...

[o3spec]

its a misfire, check your codes

[BITRBO]

Still troubleshooting mine now, and it seems to have taken a drastic turn for the worse lately (http://www.audizine.com/forum/showthread.php?t=139876). I'm not even throwing misfire codes now, so that's pretty neat

I'll let you know what I find...

[DuWerk]

That is what mine does, no misfire codes.... And I also did change the plugs.. But without misfire codes, I can't guess which coil pack to try right?

[s4twin]

still having the same problem....just put in some awe ic's and the bucking/surging went away for about 3 days. now its back........no codes. this is really annoying.

[DuWerk]

My car will run good for about 10 mins after I clear the bank 1 and bank 2 rich and lean codes...... Then the surging and bucking continues, give it 30 miles and on the engine light comes again. It is so annoying I really am sick about it.

[Mattgfx]

no codes no other problems but this with my car also.. im stage 2

someone help us.

[DuWerk]

Alright, So check this out,


My neighbor is parting out this 02 S4.... So I decide to go over and start swapping everything I possibly can to try to figure out this problem. So I figure why not try the MAF and accordion hose. I put it in, take a drive and problem solved.............

Here is what happened. I think someone else mentioned this further up in this thread. When AWE shipped me my Fueling kit, they conveniently left out the "air straightener" that is supposed to go into the larger MAF. So people would always say, "swap the MAF" and I would just put the insert into the 85mm housing and go for a run just to find it didn't help at all. So today, when I put the stock MAF housing back in there with its "grid" ( the air straightener ) it did the trick. Now my car runs smooth and there is no bucking/surging at all. The exhaust smells less rich and I am already getting better gas mileage.

I called AWE and told them and they just said, I was supposed to get the straightener and that without it, this would happen every time. I guess the 85mm MAF is so big the air makes its own path around the sensor ( which consequently doesn't stick very far into the massive 85mm housing.

Now, because I am stage 3 or RSK04 as AWE calls it, the car doesn't quite have the balls with the small MAF in there. ( only 16 lbs ) I await the straightener tomorrow and I will put it in there and see if all is good again biturbo town... LOL

I hope this helps. But I would have to say, that anyone having these issues should either examine the connection at or near the MAF or be sure their straightener is in place.

I am so happy it doesn't buck anymore... GOD DAMN!!!

Anyone going to H2O this year?


Aaron

[Allaidback]

I have the AWE stage 3 kit with fueling from 2006. Is the straightener included in this kit? What would I look for and where is it located?

[DuWerk]

Right where the MAF mounts to the airbox is where the flow straightener goes. Check to see if it is there. The damn grid is the same as one out of a Bosch 2000 style MAF but I didn't know it. When I put my kit on the grid from the Hitachi ( AKA 2001 up ) MAF didn't seem to fit, so I didn't worry about it. That is because they should have included it knowing I had a 2001.

If you are having this prob, you may want to check it out.

Aaron

[BITRBO]

IDK DuWerk... I've still got my staightener, AND I've even swapped out my MAF for a few days to see if that'd help. Nothing. Although, I just got my ride back from the shop yesterday and all they claim to have done was realign the throttle body and clear the codes... For now its running 1000% better, but I'm still noticing a slight chugging/surging between 10-20inHg (albeit much, much more subtle than before). It's almost like it comes and goes.

Just for S&G's, I logged my idle a couple times today and I have almost ZERO misfires. If I sit there long enough one will pop up ramdomly, but that's it!!! Definitely nowhere near what it was doing in previous weeks (70+ misfires/minute).

IDK, maybe the TBB alignment really helped, but I had already tried that with no results. I'm gonna watch it for the next few days, but as for now, I'm totally stumped...

[DuWerk]

Yeah, I know, I was really getting pist off at this car. but I swear its all good. I just took a 40 mile round trip tonight, no bucking, no surging, and for the most part decent boost. I saw 21 pounds a few times but only 15 sometimes still. I am happy enough for now and I now know I can take it down to Ocean City for H2O.

[Allaidback]

Took a look at the MAF and smooth all the way through, the airbox has a grid looking part to it right where the MAF hooks in...is this what I am looking for? So the straightener doesn't go inside the MAF?

[DuWerk]

My airbox didn't have that. It is open with no grid, and the maf had no grid. See if you can put the grid in your MAF. I would call AWE or whoever made the MAF and see what they have to say about that setup you have.

[WillRaceForBeer]

I've had this problem for about 6 months. So this past weekend I did a boost leak test, which came up negative. However ever since then my boost fluctuations have completely disappeared. Only explanation I have is one of 2 things, either the accordion hose was not 100% sealed before, or pressurizing the system had an effect on a sensor that normally doesn't see positive pressure.

Whatever the case I'm ecstatic. Good luck guys.

[00s4slvr]

this is going to be one of the dumbest questions probably... but what does WOT mean. I always see it and i cant ever figure out what it means... wide open throttle???

and if it is that what is wide open throttle?

[WillRaceForBeer]

this is going to be one of the dumbest questions probably... but what does WOT mean. I always see it and i cant ever figure out what it means... wide open throttle???

and if it is that what is wide open throttle?

Press the gas all the way down, and enjoy WOT.

[tike0rz]

I'm the same. Subscribed so I can remember one day to fix this problem

[S4-ORCE]

It's your injectors opening and closing really fast bc of the really low load. Its normal.

[Evilevo]

i fixed the problem. Moved to 60# injectors and a different tune!!

[momento1]

sorry to revive an old thread but this problem has come again with me...

but this time my straightener is in place!!

i get the jerky motion at part throttle in any gear..

and for the most part im only getting 15-17psi...

Im stage 3+ and normally i would see 21-23psi

and it doesnt feel quick as it was

i just recently replaced my N75 valve.. so unless that is faulty....
havent replaced my MAF in about a year....

im stumped!!

[momento1]

scratch that last post...


just went to double check and my flow straightner is missing...

mechanic forgot to put it back in a couple days ago when he had it

hopefully it fixes it

[DuWerk]

My best guess would be the MAF again. After all, the straightener influences what the MAF reads and if the MAF is dirty etc it could act the same way.
If you have your airbox cut open on the bottom or run a Cone type filter, that MAF has a better chance of getting dirty after a while ( perhaps as soon as one year).
Best thing is to meet up with someone and swap the MAF real fast and I bet it will go away.

Good luck....
I am selling my wagon if anyone wants it.....
http://www.audizine.com/classifieds/...p?product=8784

[NOTORIOUS VR]

Wow it seems I'm not the only one with these issues.

anyways, so far I've done the following:

replaced spark plugs (NGK 7's)
checked for vacuum/boost leaks
Changed MAF

I do randomly get O2 sensor codes for both front sensors, but my gas mileage is decent. And now thinking about it, it might be possible that one or both of the pre-cats are plugged causing the O2 sensors to throw a code.

I've had a code come up once for excessive boost, at which time the car felt like it wasn't building boost at all. That never happened again though and never got that code again.

Still waiting on my boost gauge.

Might possibly be a bad ECU flash (currently running an unknown flash - ~18psi spike, holds 13-14 psi).

Will post more when I find out.