A6 C7 CGQB Injection deviation

[George-92]

Hi all,

Over the last few days i first noticed a lumpy cold startup, once moving it smoothes out.
It has since developed into a rough idle even when warm. Once revs goes over 1k the roughness fades out and is not aparent after 1.5k rpm.}

As a side note since this started i have poped some Wyns gold in with my last fuel topup yesterday.

I popped on today and did some digging, there is no engine errors, however measuing injection deviation and rail pressure calibration point i have found cylinder 6 is way way out of spec.

Attached is the calibration point, I did note injector 6 was the only with a positive value.
The graph shows the injection deviation for all 6 cylinders through the rev range from idle "750" to "2.5k".
It does also show the same signs that the deviation levels out once acheiving 1.8k rpm roughly

Tuesday,28,June,2022,17:21:58:12972
VCDS -- Windows Based VAG/VAS Emulator Running on Windows 10 x64
VCDS Version: 22.3.1.4 (x64)  HEX-V2 CB: 0.4615.4
Data version: 20220407 DS337.0
www.Ross-Tech.com




                Address 01: Engine  (4G0 907 589 A)

17:21:40
  IDE01387   Injector 1: rail pressure calibration point 1 -11.10 µs
  IDE01388   Injector 1: rail pressure calibration point 2 -28.40 µs
  IDE01389   Injector 1: rail pressure calibration point 3 -0.70 µs
  IDE01396   Injector 4: rail pressure calibration point 1 -16.95 µs
  IDE01397   Injector 4: rail pressure calibration point 2 -16.10 µs
  IDE01398   Injector 4: rail pressure calibration point 3 -6.85 µs
  IDE01402   Injector 6: rail pressure calibration point 1 -10.65 µs
  IDE01403   Injector 6: rail pressure calibration point 2 33.80 µs
  IDE01404   Injector 6: rail pressure calibration point 3 -6.80 µs

What is your thoughts, i would say bad/dirty injector. Its just odd how it performs in spec when revs go up.

Thanks

 

[HMC]

Time for a compression test.
Regards HMC

 

[George-92]

Time for a compression test.
Regards HMC

This graph would show the opposite of compression was concerned. The deviation would expand as cylinder pressure increases with revs/load.

 

[George-92]

Update
Took the hunch and ordered a new injector last night.

This morning..
The dreaded roadside recovery was on hand.
Stop/start kicked in and the engine never came back on.
Engine tried to start but no ignition.

once back on the drive, and got a P0087 rail pressure too low.
Injector 6 out and I was presented with quite a messy unit.
The injector stretch bolt was hand tight loose for a start..
Injector copper washer is nowhere to be seen. Injector rubber oil seal was almost completely disintegrated.

thought I would try and blow down the injector on the bench and out came fuel from the nozzle with little resistance.. something tells me the injector has seen better days
Will try and attach an image later on

 

[George-92]

 

[JMR]

ay guacamole !

 

[aka4ajax]

Hi, I have a very similar output from my V6, but my offending injector is cylinder 3.
When you swapped out the old injector, did this cure the issue?