PLEASE HELP: Fueling or Ignition (or neither...)?>>>UPDATED

[BITRBO]

So my search for a solution to this problem still continues, but instead of boring people with all the back & forth of the original thread, I figured I just start a new one in hopes of getting some fresh ideas. Here is a link to the original thread if anyone wants some background info:

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

And here are a few video clips I took with my digital camera so you can see what is happening:

http://www.youtube.com/watch?v=5DG8827TB8o
http://www.youtube.com/watch?v=eT5cx...eature=related

So essentially I have been experiencing this slight surging/chugging sensation for a while now (~2yrs), which seems to directly correspond to fluctuations in my VAC (as seen in the videos above). It seems to happen intermittently and doesn't matter if the car is hot or cold; full of gas or not; etc., etc. It does, however, seem to get much, much better (if not completely disappear) when ambient air temp is below 60 deg. (F). For instance, it was 55 deg. (F) this morning and the car didn’t act up once even though it has been driving like shit all summer.

In an attempt to find the problem I've replaced/tested/tried all of the following, with little or no change in overall behavior:

* Multiple pressure tests at a local shop AND on my own (w/ soapy water); One (1) minor leak found at the bottom of the Y-pipe (fixed), but no change noticed
* Replaced the TBB w/ a SAMCO
* Replaced the DV's and rebuilt several times (cleaned, greased, swapped springs, etc.)
* Realigned the Throttle Actuator Valve (several times)
* Replaced both the fuel & air filters
* Swapped out the MAF, ICM's, and N75 w/ new ones
* Cleaned MAF w/ entire bottle of MAF-cleaner
* Replaced all the plugs twice (Iridiums, then Side-Fires) and coil packs w/ new Meyles
* Resistance-tested all O2 sensors and all of them around 10.4 Ohms (<than 20 is still good)
* SeaFoam treatment to intake & fuel tank
* Bypassed the N249 valve and replaced the 5-Way Check Valve that connects it it
* Replaced all the turbo inlet & outlet hoses w/ the Zena Racing kit and new clamps (except the first two turbo outlet hoses)
* Obviously logged the car at nauseum, sometimes finding misfires, other times nothing.

Despite the rough idle and slight chugging in VAC (cruising speeds), the car still pulls pretty hard at WOT (although a recent dyno session had my A/F around 13 : http://www.audizine.com/forum/showth...nce+dyno+Stage)

Unfortunately my current diagnostic methodology of replacing parts via "trial & error" has become exhausting and expensive... I have been seriously considering a different tune, but the problem seems to exist whether I'm in chipped mode or stock mode; leading me to believe its not necessarily tune related. I also don't think its mechanical (e.g. bent valve, low compression, bad wastegate, etc.) as the problem comes & goes as it pleases. Therefore I think it may be either electronic/sensor related, but IDK for sure.

Any thoughts/help/guidance is appreciated...

TIA!

UPDATE: Through some logging sessions I found that my Pass-side O2 was on the way out, and just threw a CEL the other day. I have a new BOSCH ready to install and will advise if this helps any... *fingers crossed*

UPDATE2: Replaced the pass-side O2, and the problem still exists Recent logging session shows the pass-side O2 still reading a little lean (slightly leaner than the d-side O2), but still within normal I guess (~0.82-0.84V @ WOT)

UPDATE3: FIXED!!!! If you have this problem, replace your throttle body to save time and money!!!

[BITRBO]

WTH... 28 views and nobody has any ideas??

[NOTORIOUS VR]

I see you're running a GIAC ECU... I'm almost willing to bet that its the GIAC tune.

[jameskkk3]

Sounds like it could be your tune try switching tunes with some one else and see what happens.

[BITRBO]

Yeah, like I said: It still seems to happen even if I switch back to "stock" mode w/ my flash loader; which would mean that shouldn't be a tune-related issue. IDK...

I'd love to swap M-box ECU's w/ someone to see if it helps, but there's nobody local w/ a 6MT stage II like mine...

[RolledMySTi]

Have you logged your iat's? If the car works better when cold I would expect that the car is getting screwy iat's and retarding the timing when it thinks the iat's are sky high.

[NOTORIOUS VR]

I'd love to swap M-box ECU's w/ someone to see if it helps, but there's nobody local w/ a 6MT stage II like mine...

Just grab any 6 speed box that's chipped... there's gotta be someone around... Doesn't have to be a stage anything.

As long as he's got the same maf as you it'll be direct plug and play.

[BITRBO]

Have you logged your iat's? If the car works better when cold I would expect that the car is getting screwy iat's and retarding the timing when it thinks the iat's are sky high.

No, but I'll try that next... So should I just log it during normal driving or during a FATS run? And is there some range that is considered "normal" that I can compare it to (relative to ambient temperature, of course)?

p.s. oh, and which block is that again?

Just grab any 6 speed box that's chipped... there's gotta be someone around... Doesn't have to be a stage anything.

As long as he's got the same maf as you it'll be direct plug and play.

I thought it had to be an M-Box since mine is an '01.5?? Or it's just the MAF that determines compatibility then?

Thanks guys!

[haus4]

No, but I'll try that next... So should I just log it during normal driving or during a FATS run? And is there some range that is considered "normal" that I can compare it to (relative to ambient temperature, of course)?

p.s. oh, and which block is that again?



I thought it had to be an M-Box since mine is an '01.5?? Or it's just the MAF that determines compatibility then?

Thanks guys!

You can use an H, M or T box.

[BITRBO]

^nice, thanks! Now I just gotta find someone in my area...

[P0234]

So the video is at speed, how is the vac at idle?

[BITRBO]

So the video is at speed, how is the vac at idle?

You know I never got any video at idle, but I guess it'd probably be a good idea . I'll try to get some tonight or tomorrow... Basically the needle just sits there around 19 in. Hg or so and flutters down to 17/16 in-Hg ever couple seconds or so (again, depending on the ambient temp, etc.)... Sometimes the needle won't even FLINCH at idle, but will still flutter in VAC while driving (at part throttle only).

As much as I hope (read: pray) it's not mechanical/internal, I don't want to completely discard it as a possibility (albeit not likely)... I would just think that if there were something wrong mechanically, it would act the same way all the time, but IDK for sure I guess... I mean, a bent/leaky/stuck valve would exhibit the same symptoms consistently, all the time, right?

[P0234]

Mechanical would be very rhythmic unless there is something really weird going on (partially sticky valve/lifter/???). That's really cool that the problem occurs at idle though, much easier to troubleshoot a parked car than a moving one. Get a video of it at idle first (no A/C and warmed up). You have a boost leak test kit right? Then remove the PCV hose and cap it and see if the idle gets any smoother. Next, unplug the MAF and see if it gets any smoother. If none of that smoothens the vac at idle, we'll need to do some logging.

And trust me, I know how frustrating this is. I had a 5.0 I tore apart looking for a cruising speed stutter, OMG did that drive me insane. Spent months. troubleshooting to find it was a leaky manifold gasket. I skipped over things because I KNEW it couldn't be something I just replaced (put on a new intake a few months prior).

[lbs4]

way to bring back the thread from the dead, lol 2009. are you still having the same issues this whole time?

[BITRBO]

I do have boost leak tester, just not a vacuum leak gauge. I'll try the plugging/unpluggin the PVC and MAF to see what happens...

I love this car but this problem has really driven me crazy over the last couple years... Now that you mention it, I'm a little concerned that some of the part swapping/replacing I did early on in the diagnosis may not have been very effective. That was before I had VAGCOM and ECUx, so I didn't properly log the car before and after to see if any of those changes had any real effect.

On a side note: as I mentioned at the begging of the thread, my pass-side O2 sensor has been on the way out for a while now and finally shit the bed (CEL light on now)... I kinda doubt this was my problem, but I figured I mention it anyways.

[BITRBO]

way to bring back the thread from the dead, lol 2009. are you still having the same issues this whole time?

unfortunately, yes... The funny thing is I've only put on a thousand miles since last November cause the car just sits in the garage most of the time now. I keep tinkering with it on the weekends between house projects, but nothing seems to work.

[shadwarr1]

Ya know, my car seems to have a slight chug/hesitation when it's cold only, and only when it's in a low vac. (between 15-5 in.) When's it's warmed up though it completely goes away. I've never really thought anything of it. And I can't remember if it was there when I had my K03's in.

Sorry I'm no help, just maybe trying to help knowing you're not the only one.

This may not have anything to do with it, but what about a IAT sensor? I see you mentioned it seems to get better with a colder outside ambient air temperature. Just a thought.

I too have a slight, and I mean SLIGHT rough idle, but I'm figuring I just need new plugs (also the occasational misfire at idle only, but no flashing CEL or stored codes). Last time I pulled my plugs I just cleaned them and regapped. That was 2 years ago, lol.

[BITRBO]

You know, I've thought about changing out the IAT for precisely that reason, but after buying new coil-packs, and ICM, and a MAF I was a little burned out on parts replacement.... I assume the IAT only reads temperature, and not humidity or anything else, right? Does anyone know what block it is in VAGCOM or if I can even log it?

[shadwarr1]

You know, I've thought about changing out the IAT for precisely that reason, but after buying new coil-packs, and ICM, and a MAF I was a little burned out on parts replacement.... I assume the IAT only reads temperature, and not humidity or anything else, right? Does anyone know what block it is in VAGCOM or if I can even log it?

Channel 004

THIS thread had a little info about it's function.

[P0234]

I do have boost leak tester, just not a vacuum leak gauge. I'll try the plugging/unpluggin the PVC and MAF to see what happens...

I love this car but this problem has really driven me crazy over the last couple years... Now that you mention it, I'm a little concerned that some of the part swapping/replacing I did early on in the diagnosis may not have been very effective. That was before I had VAGCOM and ECUx, so I didn't properly log the car before and after to see if any of those changes had any real effect.

On a side note: as I mentioned at the begging of the thread, my pass-side O2 sensor has been on the way out for a while now and finally shit the bed (CEL light on now)... I kinda doubt this was my problem, but I figured I mention it anyways.

Well, the 02 will def have an effect on things but you still need to make sure you have good vacuum at idle before you even bother with anything else. Until you get that, you are going to be wasting your time.

[P0234]

way to bring back the thread from the dead, lol 2009. are you still having the same issues this whole time?

yeah, the OP referred to this thread in a new thread....