2008 VW Jetta 1.4 TSI engine start idle RPM variations

Hello,
My 2008 2008 VW Jetta 1.4 TSI 122HP has some issues when started after a couple of days not used.
Upon ignition it goes to 1400 RPM and then starts its very unstable descent towards 700 RPM where it becomes stable. The 10-15 seconds in-between are hectic, the revs go up and down and the car shakes. Even after stabilizing, sometimes it feels like the engine doesn't run very "round" (if you carefully listen to it, it feels somewhat like a missfire).
This doesn't happen every time. From what I could observe it almost doesn't happen during cold weather. when it is hot outside, it happens more when the tank is less tan half full.
The spark plugs have been changed and the throttle body cleaned (not very dirty anyway).
On the tester there are some errors, but nothing related to engine management (see report below).
Does anyone have an idea what is causing this?
Thank you in advance!

No DTC's though huh?
Boy this sounds familiar like a bad fuel lift prime or other fuel related condition for pre regulation to HPP.

Read TSB's on this engine and consider installing fuel psi gauge on lift and post HPP to observe after a few days to see if prime is lost or an injector sticking open maybe.

Thank you for the answer, Jack!
I did not install the gauge yet (I need to find one first). What I managed to do, in exchange is to use the tester to monitor the HPP's parameters before the ignition and afterwards, during the functioning of the engine. As you can see in the attached images, the pressure just before ignition is 6.76 bar (after turning the key off and then to the first position for three times it rose to 7.26 bar).
During the actual ignition the pressure goes up to 75.57 bar and then it settles to 50 bar (which I understand is the normal operating pressure of the HPP).
I also did a test with the engine warmed up to 80 degrees C (temperature of the cooling liquid). Once it reached this temperature I stopped the engine and the pressure was still rising (I understand this is a pressure test for the HPP, and if there was a leakage the pressure should have dropped).
I don't know if what I wrote helps in identifying the cause of this issue, I am trying to "isolate" it. Does this help you more in figuring it out or should I stick to your first advice of installing a gauge to measure the pressure?
Thank you in advance!

https://scontent.fotp3-3.fna.fbcdn....=1be5786b57e834cc5666f5135e776d55&oe=5D564EC9

OBD is a guide, not an absolute and I trust mechanical's or DVOM & so I can cross check & to it; often it helps me find issues when the controller is lying to me & over the last 20 years from FOD tuners or the OEM!

Ok, so from the last update i managed to measure the pressure of the fuel coming from the fuel lift prime (the first video attached). Since the pressure varying a lot I bought a new one. It is not OEM, but Starline PC 1219 fuel pump.
The second movie link is with the current situation. The pressure seems to be more stable, but the engine still starts awkward. It seems to struggle a little bit less than before, but the problem is still not solved. The only benefit I can observe is that when stabilized and running idle the engine doesn't have that irregular "misfire" feeling I described in my initial posting. Another observation would be that for the same trip done before on the highway at 120km/h on cruise control now, at 130km/h I get better fuel consumption (I know there are many variables involved, and I my observation could be misleading).
Honestly if after the first movie I was sure, after the second I am not so sure I did a good thing with replacing the fuel pump in the tank.
https://www.facebook.com/alex.boanca/videos/10157377374673415/

https://www.facebook.com/alex.boanc...n81me1K-0EifQXxz7hrp9C-Ry-S8g8kgaUbBXpQXbz-GE

Any advice?
Thanks a lot!

asabiutza said:

Hello,
My 2008 2008 VW Jetta 1.4 TSI 122HP has some issues when started after a couple of days not used.
Upon ignition it goes to 1400 RPM and then starts its very unstable descent towards 700 RPM where it becomes stable. The 10-15 seconds in-between are hectic, the revs go up and down and the car shakes. Even after stabilizing, sometimes it feels like the engine doesn't run very "round" (if you carefully listen to it, it feels somewhat like a missfire).
This doesn't happen every time. From what I could observe it almost doesn't happen during cold weather. when it is hot outside, it happens more when the tank is less tan half full.
The spark plugs have been changed and the throttle body cleaned (not very dirty anyway).
On the tester there are some errors, but nothing related to engine management (see report below).
Does anyone have an idea what is causing this?
Thank you in advance!

Code:

Wednesday,05,June,2019,20:37:17:50604
VCDS -- Windows Based VAG/VAS Emulator Running on Windows 10 x64
VCDS Version: 19.6.0.2 (x64)  HEX-NET CB: 0.4505.4
Data version: 20190529 DS308.0
www.Ross-Tech.com


VIN: WVWZZZ1KZ8M174332   License Plate: 
Mileage: 125990km-78286mi   Repair Order: 



--------------------------------------------------------------------------------
--------------------------------------------------------------------------------


Chassis Type: 1K (1K0)
Scan: 01 03 08 09 15 16 17 19 25 42 44 46 52 56 62 72

VIN: WVWZZZ1KZ8M174332   Mileage: 125990km-78286miles

01-Engine -- Status: OK 0000
03-ABS Brakes -- Status: OK 0000
04-Steering Angle -- Status: OK 0000
08-Auto HVAC -- Status: OK 0000
09-Cent. Elect. -- Status: OK 0000
15-Airbags -- Status: OK 0000
16-Steering wheel -- Status: Malfunction 0010
17-Instruments -- Status: OK 0000
19-CAN Gateway -- Status: OK 0000
25-Immobilizer -- Status: OK 0000
42-Door Elect, Driver -- Status: OK 0000
44-Steering Assist -- Status: OK 0000
46-Central Conv. -- Status: OK 0000
52-Door Elect, Pass. -- Status: Malfunction 0010
56-Radio -- Status: OK 0000
62-Door, Rear Left -- Status: OK 0000
72-Door, Rear Right -- Status: OK 0000
-------------------------------------------------------------------------------
Address 01: Engine (CAX)       Labels: 03C-906-022-CAX.clb
   Part No SW: 03C 906 022 J    HW: 03C 906 022 J
   Component: MED17.5.20      G   8644  
   Revision: D5H03---    Serial number: VWX7Z0H4243045
   Coding: 0000072
   Shop #: WSC 10102 599 84138
   VCID: A3066DE76210D4572C-80F6

No fault code found.
Readiness: 0000 0000

-------------------------------------------------------------------------------
Address 03: ABS Brakes        Labels: 1K0-907-379-MK70.lbl
   Part No: 1K0 907 379 P
   Component: ASR FRONT MK70      0105  
   Coding: 0017025
   Shop #: WSC 00066 000 00000
   VCID: BFCEC197EEB890B728-80EA

No fault code found.

-------------------------------------------------------------------------------
Address 08: Auto HVAC        Labels: 1K0-907-044.lbl
   Part No SW: 1K0 907 044 DA    HW: 1K0 907 044 DA
   Component: ClimatronicPQ35 130 1213  
   Revision: 00130023    Serial number: 00000000000000
   Shop #: WSC 00000 000 00000
   VCID: E99A3FCFC0BCCE07A6-80BC

No fault code found.

-------------------------------------------------------------------------------
Address 09: Cent. Elect.        Labels:. 3C0-937-049-30-H.lbl
   Part No SW: 3C0 937 049 AJ    HW: 3C0 937 049 AJ
   Component: Bordnetz-SG     H54 2202  
   Revision: 00H54000    Serial number: 00000000952804
   Coding: 81078E0700041500470A00000F00000000095D035C00010C000000000000
   Shop #: WSC 00066 123 12345
   VCID: F1AA57AFE86C36C7EE-80A4

   Subsystem 1 - Part No: 1K1 955 119 E  Labels: 1KX-955-119.CLB
   Component: Wischer 300408 021  0501  
   Coding: 00038805
   Shop #: WSC 00066  

No fault code found.

-------------------------------------------------------------------------------
Address 15: Airbags        Labels: 1K0-909-605.lbl
   Part No SW: 1K0 909 605 T    HW: 1K0 909 605 T
   Component: 2J AIRBAG VW8   020 2300  
   Revision: 05020000    Serial number: 0038PD1W1GN-  
   Coding: 0012874
   Shop #: WSC 00066 000 00000
   VCID: BD32BB9FE4B482A73A-80E8

   Subsystem 1 - Serial number: 6332MSME3672732DE

   Subsystem 2 - Serial number: 6342MSME32521415 

   Subsystem 3 - Serial number: 6351HSME141C4D47D

   Subsystem 4 - Serial number: 6361HSME141C24620

No fault code found.

-------------------------------------------------------------------------------
Address 16: Steering wheel        Labels: 1K0-953-549-MY8.lbl
   Part No SW: 1K0 953 549 BG    HW: 1K0 953 549 BG
   Component: J0527           051 0100  
   Coding: 0002021
   Shop #: WSC 00066 000 00000
   VCID: F8BC6A8B8B16678F29-80AC

   Subsystem 1 - Part No: XXXXXXXXXXX 
   Component: E0221           002 0010

5 Faults Found:
00576 - Terminal 15 
            012 - Electrical Fault in Circuit
00883 - Ignition Switch (D) Terminal S 
            012 - Electrical Fault in Circuit
00884 - Ignition Switch (D) Terminal X 
            012 - Electrical Fault in Circuit
01744 - Ignition Switch Terminal P (D) 
            012 - Electrical Fault in Circuit
00885 - Ignition Switch (D) Terminal 50 
            012 - Electrical Fault in Circuit - Intermittent

-------------------------------------------------------------------------------
Address 17: Instruments        Labels: 1K0-920-xxx-17.lbl
   Part No SW: 1K0 920 874 A    HW: 1K0 920 874 A
   Component: KOMBIINSTRUMENT 3HL 2216  
   Revision: V0002000    Serial number: VWX7Z0H4243045
   Coding: 0023103
   Shop #: WSC 10102 599 176587
   VCID: AB1685C70AC01C1794-80FE

No fault code found.

-------------------------------------------------------------------------------
Address 19: CAN Gateway        Labels:. 1K0-907-530-V3.clb
   Part No SW: 1K0 907 530 L    HW: 1K0 907 951 
   Component: J533  Gateway   H07 0052  
   Revision:   H07 01    Serial number: 260308F2013695
   Coding: E9807F060002021002
   Shop #: WSC 00066 000 00000
   VCID: B02C92AB23E67FCFA1-80E4

No fault code found.

-------------------------------------------------------------------------------
Address 25: Immobilizer        Labels: 1K0-920-xxx-25.clb
   Part No SW: 1K0 920 874 A    HW: 1K0 920 874 A
   Component: IMMO            3HL 2216  
   Revision: V0002000    Serial number: VWX7Z0H4243045
   Shop #: WSC 00000 000 00000
   VCID: AB1685C70AC01C1794-80FE

No fault code found.

-------------------------------------------------------------------------------
Address 42: Door Elect, Driver        Labels:. 1K0-959-701-MIN3.clb
   Part No SW: 1K0 959 701 P    HW: 1K0 959 793 L
   Component: J386  TUER-SG FT    1133  
   Revision: 32008001    Serial number: 00000260088418
   Coding: 0000180
   Shop #: WSC 00066 000 00000
   VCID: BB36B587FAA08C9704-80EE

No fault code found.

-------------------------------------------------------------------------------
Address 44: Steering Assist        Labels: 1Kx-909-144-G2V3.clb
   Part No: 1K1 909 144 M
   Component: EPS_ZFLS Kl.069 H08 1901  
   Shop #: WSC 00066 000 00000
   VCID: B522A3BFDC845AE7F2-80E0

No fault code found.

-------------------------------------------------------------------------------
Address 46: Central Conv.        Labels:. 1K0-959-433-MAX.clb
   Part No SW: 1K0 959 433 BT    HW: 1K0 959 433 BT
   Component:    KSG PQ35 G2  020 0204  
   Revision: 00020000    Serial number: 00000000000000
   Coding: 98900A0001060C7F2D048C0D70084FC6F0FC00
   Shop #: WSC 00066 123 12345
   VCID: 83460D67C2D034570C-80D6

   Subsystem 1 - Part No: 1K0 951 605 C
   Component: LIN BACKUP HORN H03 1301

   Subsystem 2 - Part No: 1K0 951 178 A
   Component: Neigungssensor  003 0203

   Subsystem 3 - Part No: 1K0 951 178 A
   Component: Innenraumueberw.003 0203

No fault code found.

-------------------------------------------------------------------------------
Address 52: Door Elect, Pass.        Labels:. 1K0-959-702-MIN3.clb
   Part No SW: 1K0 959 702 P    HW: 1K0 959 792 L
   Component: J387  TUER-SG BT    1133  
   Revision: 32008001    Serial number: 00000078588412
   Coding: 0000180
   Shop #: WSC 00066 000 00000
   VCID: BC34B69BFFAE8BAF0D-80E8

1 Fault Found:
00097 - Front Passengers Central Locking (Safe) Motor (V162) 
            012 - Electrical Fault in Circuit
             Freeze Frame:
                    Fault Status: 01101100
                    Fault Priority: 3
                    Fault Frequency: 2
                    Reset counter: 223
                    Mileage: 125980 km
                    Time Indication: 0


-------------------------------------------------------------------------------
Address 56: Radio        Labels: 1K0-035-1xx-56.lbl
   Part No: 1K0 035 186 AD
   Component: Radio GR0       034 0033  
   Revision: 0003404S    Serial number: VWZ2Z2H6540654
   Coding: 0040400
   Shop #: WSC 00066 000 00000
   VCID: E89C3ACBDBB6F70FB9-80BC

No fault code found.

-------------------------------------------------------------------------------
Address 62: Door, Rear Left        Labels:. 1K0-959-703-GEN3.clb
   Part No SW: 1K0 959 703 P    HW: 1K0 959 795 G
   Component: J388   TUER-SG HL   1120  
   Revision: 11006001    Serial number: 00000003011286
   Coding: 0000144
   Shop #: WSC 00066 000 00000
   VCID: BD32BB9FE4B482A73A-80E8

No fault code found.

-------------------------------------------------------------------------------
Address 72: Door, Rear Right        Labels:. 1K0-959-704-GEN3.clb
   Part No SW: 1K0 959 704 P    HW: 1K0 959 794 G
   Component: J389   TUER-SG HR   1120  
   Revision: 11006001    Serial number: 00000003006863
   Coding: 0000144
   Shop #: WSC 00066 000 00000
   VCID: BE30BC93E9B299BF23-80EA

No fault code found.

End----(Elapsed Time: 01:26, VBatt start/end: 11.9V/11.9V. VIgn 11.9V)-----

Click to expand...

Consider carbon cleaning if not done so....and bear in mind that precatalyst warm up period exhibits such symptoms....I think you got misfires but below MIL detection threshold....log misfire counters on VCDS and watch in real time during the engine stuttering episode....as Jack has said,worth checking TSB for this engine,I recall struggling with faulty injector valves on a Golf 6 with similar engine,only to later realise VW updated them to a newer revision

asabiutza, FP look good enough for ignition.

Assume last shot is KOEO, (key on engine off.) DON'T know if there is anything to be gleaned from boost specified and actual not congruent, but maybe a software VAG thing as said thought it not running as no RPM pid.

Did have a Jetta that exhibited same problem, was over pressure oil pump holding open hydraulic lifter for first minute or so of start up. Was not consistent, but a real problem, would produce over 100psi when cold.

Would be interested to graph manifold pressure (I,E, ) boost in case of turbo and see if manifold pressure is fluctuating during this. Would think at idle would only produce 1 psi at most, but curious if it is going into negative, I.E less than atmosphere 1000 bar at sea level, don't know your elevation.

Understand with rough idle some of this is going to happen but maybe learn something.

Don't know of VAG allows view of oil pressure, might watch it and see if yours is high, once warm thins and lifter problem will go away, just a thought.

LARIMORE