*******SOLVED********
See page 3 for details.
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After a long exhausted couple of weeks trying to chase down this issue, I thought I'd come to the resident experts here on 6SO. I've done my due dilligence and have searched until my hearts content on the internet for this. I'm very mechanically minded as well as a programmer, so I feel like I have a very good grasp on these issues (B5 S4's anybody )

Issue

Car drives amazing below 4k partial OR full throttle. But the car has hesitation/falls on its face/breaks up in acceleration/ whatever you want to describe it as from about 4000 RPM to 5000/5200 RPM. Then it pulls just fine to redline, no hiccups. Only CEL's in the past were from boost leaks, and these crop up after driving the car for a bit then I'll be idling and it'll just pop on in traffic.. P0171, P0174. Never any other codes besides the ones for a bad MAF last year when I replaced it (including the ABS/PSM lights).

What's been replaced

MAF - (1 year ago, new Bosch unit)
Plugs, updated 997 coilpacks, fuel filter (15k miles ago, 2.5 years ago)
Fuel pump (last week)

What's done to the car?

EPL 91 Tune
72 lb Injectors
Billet K16s
EVOMS Intake
EVOMS Diverter Valves & Silicon F Hose
Speedtech 3" Xcellerator Catless Exhaust

What I've tried

Took the car down to a local Porsche Indy, had them take it for a spin. They tightened up a drivers side intercooler hose after a boost leak test, and still saw the same problem @ 4k. Put a fuel pressure guage on it and saw it going all over the place when the car reached 4k, so we put a fuel pump in it, no dice, still same issue of hestitation @ 4k-5k RPM

I did some logging today to dig into this a bit further and have attached it to this post. I did a 3rd gear pull from 2k RPMS to ~6.5-7k RPMS. Parameters measured can be seen in the attached spreadsheet.

I noticed my MAF is being pegged @ 5v (max possible voltage it can read) right when it's hitting 4k rpm, but the MAF is continuing to measure increase in Air (based on column F, rows 28-44). Is this normal? Does it need to be replaced again?

Also, IDC's look good, AFR seems to be stupid rich in high load/high rpms/high boost (as you can see in Column K, rows 28-44) based on the Oxygen sensing bank 1 Lambda Value.

Timing seems to be all over the place in 4k-5k rpm range also...

I'm running out of ideas and I don't want to start replacing parts just to replace them Thanks in advanced guys...

 

Nevermind... missed the "1 year ago" on the MAF.

My guess would be plugs.

 

While I would lean towards agreeing with you, don't you think I would have seen a misfire code by now? I haven't seen one...

 

Send the log to your tuner, have him take a look.........also start cheapest first........

 

I'm experiencing the exact same problem. I think is MAF related or plugs related. I will try to replace the MAF to begin with and if the problem still exists i will replace plugs.

 

plugs
coils
failing maf
dirty TB
least probably a boost leak? possibly btw maf and turbo inlets. wouldn't that account for odd readings?

some or all of the above. but going with plugs/coils/maf in that order. all just wag's. plugs are so cheap and get fried so much more quickly on tuned cars than on stock that they should be changed every 10k/15 miles as a matter of course. gl with it. at least you can do all that stuff..and hopefully you're running a paper mahle!

 

very rich lambda value under load...boost leak?

maf goes very early at the sensor limit....try it without maf (no costs) for a short test

problems at high boost/load and acceleration spark plugs and coils...

deviation at requested boost to actual boost....boost leak or correct adjusted wastegates?

 

I had a similar issue a few months back. It could me a number of items, but for me it was plugs (even though I had them changed about a year ago)

 

Seems to be the going argument, may just tackle plugs and see what happens.

Bingo, just waiting for the tuner to call back

Well I had the shop boost leak test the car and they only tightened up the hose that's been problematic and described in my original post. Although, I am going to take a gander at the vacuum T underneath the throttle body and make sure it looks ok..

Can you elaborate on the 'correct adjusted wastegates' comment? I have 1 Bar WGs with these Billet k16s I didn't mention up top.

This seems to be resonating more. Suggestions on plugs?

 

http://www.pelicanparts.com/catalog/..._pg1.htm#item2
Spark Plug - Bosch FR-6-LDC , Beru 14 FR-6 LDU, (7410)
Part #: 999-170-195-90-M47

i wouldn't mess with "success" good enough for gt2, now the recommended oem replacement for 996 when they originally used "5" heat range. this for tuned car. cant go wrong. pre gapped out of the box.. but you can dbl check. i go with .027.

 

Thanks for the link, Tony@EPL called me back today regarding this. Advised plugs as well, these specifically.. Ordered them via Amazon (for a bit cheaper ). Also free next day shipping...Prime can be lovely.


Thanks for the help 02996ttx50

 

my pleasure. I've had a good day.. now i'll be wrong about everything for a week! lol.

gl with them .. and merry xmas!

 

I agree Mark sounds like a leak before the turbos.

Check the hose between the airbox and the turbo inlet pipe a small leak there will cause exactly what you describe.

Cheers

 

hey buddy.. heard you did the F 1st console riser.. you still have that gt3 console delete??

 

yeah i still have the gt3 delete bro

do you want it ?

PM me