Acceleration issue

B6/7 S4/RS4
#51

Hope you can view them.

#52

Your long term fuel trims from block 32 indicate a lean condition at idle and load. The LTFT at idle is actually in spec, but the LTFT at load is pretty bad. This indicates a lean fueling issue - the motor is not getting enough fuel or is getting too much air. The fuel trim numbers don’t indicate a vacuum leak to me since the short term is way negative at idle and WOT. Are you getting any lean codes?

The O2 lambda actual/specified in block 31 seem okay to me. Can anyone else comment on these numbers?

I would start with the following:

  1. Confirm that your O2 sensors are connected to the proper connectors. Cross connected O2 sensors can do crazy things to the fuel trims like we’re seeing in these logs. Have you changed your O2 sensors recently?

  2. With the car running check fuel pressure at the fuel rail with VCDS measuring block 106. I’m not sure what spec is for the S4, but it should increase with engine load. Can someone provide the spec for this number?

#53

Also take it easy on the high rpm pulls until we know why it’s running lean.

#54

Clarification on fuel pressure data from ross-tech wiki:

Group 103
Field 1: Fuel Pressure (Low), Specification: 2800…7200 mbar
Field 2: Fuel Pump Adaptation, Specification: -1000…+1000 %

Group 106
Field 2: Fuel Rail,Pressure (actual): 55% or below is normal at idle
55% to 60% is a gray area, it may be okay, but may indicate a problem
Above 60% implies there is a failure or restriction
-Causes of low pressure can include kinks or restrictions in fuel lines
-Fuel filter issues including restricted/clogged or incorrect part number
-Failing lift pump in fuel tank.

Group 140
Field 3: Fuel Rail Pressure (High), Specification: 25.0…110.0 bar
Increase the Engine Speed while checking this value, the Pressure has to rise with the Engine Speed.

Note These data specifications are specifically mentioned in reference to the 2.0 TFSI, but the same groups can be used for analysis.

#55

Okay when I get a chance I will log the fuel pressure. It will be later today.

#56

Good, and can you please describe your symptoms once more and provide any codes the car is showing?

#57

https://docs.google.com/document/d/1MW6WWoqfWCRxVs2qjOTiLw9So8IEuJTISHp_VqBpF9E/edit

These are the codes. While I’m cruising on the freeway about 70-75 the car will through the MAF code and it will sputter, then try to get away from me, and sputter again, then drive normal.

#58

The P0101 code threw me for a second in regard to the fuel trim analysis, but there’s a technical bulletin for your car saying low fuel pressure can cause MAF codes.

https://i.imgur.com/xj7VOUj.png

I’m still sticking with a fueling issue as the primary, but check the things on that list too. I can post the procedure for checking the MAF sensor if you need.

#59

I just put a new one in. Doubt it’s the MAF. That means I got 2 bad new ones. I’ll try the fuel pressure measuring blocks

#60

There could be electrical problems causing the MAF to malfunction. Does it read between 2 and 5 g/sec at idle? Did you check voltage on the harness connector?

#61

at idle it is between 5-7 g/sec.

#62

also the ecu does not support block 103 106 140

#63

The higher MAF rate at idle is probly due to the supercharger. Make sure you check confirm good voltage on the connector harness pin 3.

Search the advanced measuring block interface for anything related to fuel or pressure, they might be under different groups on your car. If not you’ll have to check fuel pressure manually. The videos in this thread might help: http://audirevolution.net/forum/index.php?topic=468.0

#64

looked for the fuel related stuff through the advanced measuring blocks and nothing. ill measure the voltage again.

#65

Voltage was good

#66

Mine reads the same at idle.

Try logging channels 3 and 210 with the rpms at idle, 2K, 3K, and 4K rpms for about three seconds each. Both with the MAF plugged in and then with it unplugged.

Channels 103, 106, and 140 were not used until the FSI engines came out because these MPI V8s are more concerned with the duty cycle of the fuel pump. The fuel filter limits the pressure to the rail anyways. When was the last time that you changed your fuel filter?

I am wondering how did you connect the longer pigtail for the MAF connector as part of the SC kit? I think JHM sends pink heat shrinkable butt connectors for 20-22 gauge wire with the kit if I remember correctly. Instead of that I used smaller yellow heat shrinkable butt connectors for 24-26 gauge wire to get a tighter connection.

#67

I changed the fuel filter within the past 20k miles. As for the connector, JHM gave me the plug and play one. I was getting the codes with that one. I sent the car all the way to JHM for this exact problem. They changed my plug and play one to the pig tails with butt connectors. shipped my car back to me and i still get the same problem. i didnt like the butt connectors so i soldered the wires and shrink wrapped them. I can’t be ship my car again. cost too damn much.

#68

I’m beginning to think my ecu is done. i will check fuel pressure tomorrow.

#69

Okay your fuel filter shouldn’t be the issue than.

I didn’t even know that JHM released a plug and play extension. You probably mentioned it a while ago but I forgot if you did. My kit was so early that I had to use butt connectors. A lot of people don’t like them but they work if done correctly and I have lots of practice since Audi OFFICIALLY hates soldering. If the wires are soldered then I doubt that is the issue.

Can’t blame you about the shipping costs. From the research that I have done, it is cheaper or on par for me to drive to Cali in four days (including hotel rooms plus food and fuel) and fly back home then shipping my car to JHM.

Here is a log of my car from last year. Please remind me what mods that you have other than the SC.

http://i284.photobucket.com/albums/ll37/Jimmybones777/S43rdgearlog3202014pic1_zps75db38a0.jpg

http://i284.photobucket.com/albums/ll37/Jimmybones777/S43rdgearlog3202014pic2_zps02711851.jpg

http://i284.photobucket.com/albums/ll37/Jimmybones777/S43rdgearlog3202014pic3_zpsfd0b1755.jpg

Comparing the grams per second readings between my car to yours at different rpms:
2000 rpms - 78.06 to 79.17 = Your is +1.11
2520 rpms - 97 to 93.97 = Mine is +3.03
3040 rpms - 122.31 to 112.15 = Mine is +10.16
3520 rpms - 149.08 to 139.44 = Mine is +9.64
4000 rpms - 180.53 to 162.25 = Mine is +18.28
4520 rpms - 208.89 to 188.97 = Mine is +19.92
5080 rpms - 234.58 to 210.72 = Mine is +23.86
5560 rpms - 262.22 to 238.19 = Mine is +24.03
6080 rpms - 288.56 to 263.28 = Mine is +25.28
6440 rpms - 315.44 to 285.03 = Mine is +30.41
6840 rpms - 329.00 to 301.03 = Mine is +27.77

So it seems to me that your car is getting chocked off somewhere. Most of the way from 4K rpms on my car is reading between 18 to 30 grams per second more than yours. That is really where the blower starts to work its magic anyways. Even before that though my car is still reading around 10 grams per second higher than yours from 3K rpms till 4K rpms.

Do you have the non-collapse spacer installed in the inlet hose for the SC? Badtoyz had an issue where the inlet hose was collapsing on his car. Also just wondering but do you have the stock MAF boot because I have the 034 MAF boot?

#70

I have the stock MAF boot. I do have the non collapse spacer. I have catless headers V1. FI cat back. Ported IM and spacers. 5r clutch. Shifter trio.
Pretty much everything except built motor and heads and nitrous.