Acceleration issue

B6/7 S4/RS4
#1

Over the last 6 months my 07 S4 has developed an issue accelerating in the lower RPM’s. At first it was very intermittent but now it happens quite consistently. The car has 91k miles on it but I have done a ton of preventative maintenance and besides for this issue the car has a clean bill of health. I am most likely supercharging it by the end of the year but want to get this sorted out before I shell out the dough to JHM.

The issue is under medium acceleration from about 2k rpm to 3800 rpm sometimes the car sputters and falls flat on its face. It feels like it is misfiring or choking to a certain point then the power kicks in once in the higher RPM. You can compare it to driving for the first 30 seconds on a cold start before the motor smooths out. It is very jumpy and with catless exhaust it seems to almost backfire and pop when this is happening. If I’m accelerating lightly it is smooth all the way to redline. It is very noticeable when downshifting to second when say I’m rolling a stop sign then accelerating or downshifting to third to take a turn and then get back on the gas.

Once it gets passed 3800 or 4k rpm the car is a beast and feels completely normal. There is no CEL and I have scanned it probably 15 times with no codes. I have tried to do a throttle body alignment through vag-com but not sure if that worked correctly. After it was done the max value when the gas was mashed was 86% and the adaption step counter never changed, however it said the adaption was complete.

What should I look into next? MAF? Throttle body? Fueling?

#2

When I experienced the same symptoms it was my fuel filter. How many miles since your last change?

#3

You might have a bad throttle body or look to see if your intake flap is working properly.

With the car off but with the key on to accessory. Look at block 003 for throttle. Then got WOT and make sure it gets to 100%

The maintence question is a good one how long since each maintenance thing was done.

#4

When the car sputters are you getting a flashing CEL on the dash? A full throttle sputter is generally linked to a fuel issue. Can you duplicate the sputter over and over and over? Or will it do it once and then not again for sometime?

#5

Thanks for the responses. Here’s a link to EVERYTHING I’ve put into the car. Mods and maintenance.

https://docs.google.com/spreadsheets/d/19rk5y8oLINVKtn6enLuCDMG7YwOaos0GigtwL63LBqc/edit?usp=sharing

Filter was done about 20k ago. If the car wasn’t getting enough fuel wouldn’t it throw a code?

I’ll give that a go today. I just repaired the intake flap with the repair kit. Originally that’s what I thought was causing this problem but it’s working perfectly now so that’s obviously not the case.

No flashing CEL, no codes ever. When I’m full throttle it doesn’t seem to do it as bad as frequently. The easiest way to recreate the problem is a 3rd gear pull from about 1500 rpm at 30-50% throttle. It will sputter about half the time.

#6

Not saying you don’t have an underlying issue, but my opinion and experience is these 4.2l cars HATE being low in the RPMs.

They really just don’t feel right under 2000 even 3000 RPMs in any gear, stock or tuned w/mods. I probably waste a ton of gas, but I let that baby breathe when I’m driving, I understand there are different circumstances when daily driving in traffic and what not, but I think you may just be feeling the engine “lugging” if you arent experiencing and DTCs. You have great maintenance practices and awesome parts.

This has been happening for some time right? Probably noticed it after the downpipes and IM? I think it’s just more noticeable than it was stock because you can hear the engine more by way of the exhaust.

#7

I’ve been tuned and on catless downpipes for almost three years now but the issue has come up in the last 6 months and has started happening more and more frequently. Something is definitely going on. When it doesn’t happen the car is smooth and powerful. When it happens if feels like the car is down three cylinders temporarily.

I agree with you that you gotta let these cars breathe and open it up. The car was made to be driven, hard, and I do that plenty.

#8

Justin, just checked the throttle in VCDS. Seems to be fine, opens to 99.6% and operates normally. I’m going to run some logs in the next couple days. Any other blocks I should log other than 003/020/021?

#9

You can grab a log of that if you want. What your going to really need is blocks 003-001-014

Make sure you log when the car is breaking up and delete anything in the log that’s not including the studdering part and just a few seconds before it happened

#10

Before I did my timing service, my car used to fall flat on its face for like a second at a time randomly during 50% or greater throttle. One of the camshaft adjusters being at fault. Hopefully this isn’t the case for you :-\

#11

Hopefully not. Was your car throwing any codes?

#12

Not until it started doing it so bad it went into limp mode. Then I got codes:
P0011
P0300
P0301
P0302
P0303
P0304

#13

With the intermintent issue your getting don’t expect codes.

#14

Got a chance to log the car today. I’m not very good at interpreting these so any input would be greatly appreciated. It seems like the sputtering is lining up with the misfires. After doing the pulls I scanned the car and finally got a P1128 code. Looks like the P1128 could be a faulty MAF, O2 sensor problem or bad injector according to the ross tech wiki. Would this code and my symptoms be related?

Logs:
https://docs.google.com/spreadsheets/d/1sGSApLzV5fFiNwy_69cLH35x8ZUt5oIvP_9wSMagmc8/edit?usp=sharing

https://docs.google.com/spreadsheets/d/18lXTYW8x9j_sLjZOgfQ7afWRm_eQwPydSX4UeHF9kas/edit?usp=sharing

Code:
Readiness: 0000 0001
Sunday,24,August,2014,12:27:32:42923
VCDS – Windows Based VAG/VAS Emulator
VCDS Version: 12.12.2.0 (x64)
Data version: 20140212

Dealer/Shop Name: Kelsey’s Auto Body Inc.

            Address 01: Engine       Labels: 079-910-560-BBK.lbl

Control Module Part Number: 8E2 910 560 C HW: 8E2 907 560
Component and/or Version: 4.7L LC/93+JHM G 0010
Software Coding: 0007711
Work Shop Code: WSC 06325 000 00000
VCID: 275706F2964ABF26FAD-8072
1 Fault Found:

004392 - Fuel Trim; Bank 1 (Mult)
P1128 - 001 - System too Lean - Intermittent
Freeze Frame:
Fault Status: 00100001
Fault Priority: 0
Fault Frequency: 2
Reset counter: 255
Mileage: 147736 km
Time Indication: 0

         Freeze Frame:
                RPM: 1926 /min
                Load: 14.1 %
                Speed: 61.0 km/h
                Temperature: 93.0°C
                Temperature: 30.0°C
                Absolute Pres.: 1010.0 mbar
                Voltage: 13.843 V

Readiness: 0000 0001

#15

The bad part it your code didn’t show up in the range of the issue. The good news is the logs showed there is a big issue.

One bank is adding 6% fuel while the other bank is removing 8% fuel. So the car is all over the place. With that big of a swing check the 02s and maf. I would unplug the MAF and drive though the same RPM and see if it does it.

Also with that kind of out of range you could have a odd vac leak. that comes out under that RPM range.

#16

Thanks for the advice. All 4 of the O2’s were replaced 12k miles ago so hopefully that isn’t the issue. I’ll give that a shot with the maf tomorrow

#17

you can see the fuel starts to get really out of control right before you break up. now its just trying to figure out what part caused that. Also look to make sure you don’t have any vac leaks.

#18

Gave this a go and there was no sputtering however the car was definitely down on throttle response. I’m guessing this is to be expected with the MAF unplugged?

#19

Yes the MAF tells the motor what air to expect and the reactions are much quicker. If you unplugged the maf and didn’t get any sputtering that’s a good sign it’s the maf or a vac leak.

#20

When I fixed the intake flap I checked for, and found one vac leak so hopefully a new MAF will take care of everything