:( Very lumpy idle, backfiring

Apr 12, 2008
539
1
Well, i am not sure about leakdowns, i think my mechanic just measured compression..i will have to ask him if he can do leakdown test..
But, i am not sure if that kind od bad compression can cause very unstable idle..
I mean car starts fine, and even drives normal..
 
Last edited:
Apr 12, 2008
539
1
Ok, cylinder head was removed, valve seats were bad, leaking...now compression is ok, around 12 bar on each cylinder, but car still idles like crap

I tried so far...diferent fuel pump, diferen fpr, difrferent DV, different TB, changed intire pcv system, different injuectors...
Today i tried my luck with ECU..
Here is what i find...is oxidation posibbly my problem?



 
Apr 12, 2008
539
1
Tried different coils, plugs..
Last night i put a3 ecu and car is now working ok..however, ecu connectorh had stretched rubber seal inside and couldnt fit 100% properly
In a few days i will open ecu and check for moisture and oxidation.
 
Apr 12, 2008
539
1
VCDS Version: Release 12.12.0 (x64)
Data version: 20130910

Friday,04,November,2016,22:38:01:62939

Chassis Type: 1M (1M - Seat Leon (2000 > 2005))
Scan: 01 02 03 08 15 17 19 22 35 36 37 46 56

VIN: VSSZZZ1MZ5R074024
-------------------------------------------------------------------------------
Address 01: Engine Labels: 06A-906-032-AJQ.lbl
Part No: 06A 906 032 SJ
Component: 1.8L R4/5VT 0010
Coding: 11510
Shop #: WSC 00000
VCID: 78FF0E6B582690DEAC3-5000
VSSZZZ1MZ5R074024 SEZ7Z0E2979246

5 Faults Found:
17705 - Pressure Drop between Turbo and Throttle Valve (check D.V.!)
P1297 - 35-00 -
16795 - Secondary Air Injection System
P0411 - 35-00 - Incorrect Flow Detected
16684 - Random/Multiple Cylinder Misfire Detected
P0300 - 35-00 -
16685 - Cylinder 1
P0301 - 35-00 - Misfire Detected
16686 - Cylinder 2
P0302 - 35-00 - Misfire Detected
Readiness: 0000 1100

-------------------------------------------------------------------------------
Address 03: ABS Brakes Labels: None
VCID: 55A167DFBFF48DB6975-5000

No Faults Found
or DTCs not supported by controller
or a communication error occurred

-------------------------------------------------------------------------------
Address 08: Auto HVAC Labels: 1M0-820-043.lbl
Part No: 1M0 820 043 E##
Component: ###ö###########ö###ö1M08
Shop #: 1######ö###ö
VCID: 428BAC834E7A0A0EC27-2580
Note: Excessive Comm Errors


-------------------------------------------------------------------------------
Address 15: Airbags Labels: 6Q0-909-605-VW5.lbl
Part No: 1C0 909 605 A
Component: 39 AIRBAG VW51 0A 0008
Coding: 13113
Shop #: WSC 06401
VCID: 224B0C03AE3A2A0EA27-5000

No fault code found.

-------------------------------------------------------------------------------
Address 17: Instruments Labels: 1M0-920-xx2-17.lbl
Part No: 1M0 920 822 G
Component: KOMBI+WEGFAHRSP VDO V06
Coding: 05124
Shop #: WSC 00833
VCID: 2C57E23BDCFEEC7E18B-5000
VSSZZZ1MZ5R074024 SEZ7Z0E2979246

No Faults Found
or DTCs not supported by controller
or a communication error occurred

-------------------------------------------------------------------------------
Address 19: CAN Gateway Labels: 6N0-909-901-19.lbl
Part No: 6N0 909 901
Component: Gateway K<->CAN 0001
Coding: 00006
Shop #: WSC 06402
VCID: F0EFB64BB056489EE43-5000

2 Faults Found:
01312 - Powertrain Data Bus
37-10 - Faulty - Intermittent
01314 - Engine Control Module
49-10 - No Communications - Intermittent

-------------------------------------------------------------------------------
Address 46: Central Conv. Labels: 1C0-959-799.lbl
Part No: 1C0 959 799 F
Component: 9V Komfortgerát HLO 0004
Coding: 00257
Shop #: WSC 00833
VCID: 3A7BD46326AA42CE9A7-4A3A

Subsystem 1 - Part No: 1C0959801B
Component: 9V Tõrsteuer.FS KLO 0202

Subsystem 2 - Part No: 1C0959802C
Component: 9V Tõrsteuer.BF KLO 0202

Subsystem 3 - Part No: 1C0959811A
Component: 9V Tõrsteuer.HL KLO 0202

Subsystem 4 - Part No: 1C0959812A
Component: 9V Tõrsteuer.HR KLO 0202

2 Faults Found:
01359 - Internal Central Locking Switch; Passenger Side (E198)
27-10 - Implausible Signal - Intermittent
00931 - Locking Module for Central Locking; Rear Right (F223)
27-10 - Implausible Signal - Intermittent

End ---------------------------------------------------------------------

Tried start the car with MAF unplugged, still idles like crap...
What measuring blocks should i watch for bad idle?
I am quite sure that there is no boost leak..is it possiblr to have no boost leak, but a big vac leak? I was pressurising intake manifold all the way starting from TIP..and there was no leaks, except just a little bit around injectors, but barely...
Now, when car idles like crap i can hear loud sucking noise thru cone filter, and also in vac line that goes on top of throttle body...
 
Apr 12, 2008
539
1
So, in the summer my idle was screwed few times...this were the codes

P0122 -powertrain
throttle pedal/postiion sensor switch A circut low input


p0222 - powertrain
throttle/pedal position sensor/switch B circut low input


p0221 - powertrain
throttle/pedal position sensor/switch B circuit range/performance problem

All i did was clear them and was driving normaly for few hundreds kilometers and then it would happen again...
Weirdly, now i dont have that code, but i tried to log throttle pedal and it oscilates from 1.5 to 2.5 degress
Also, for a second i lost info in measuring blocks, got quick error message, and then got data again..
And, when i pressed throttle just a little bit, like 1/10 or 1/20 of full threottle, rpm slowly got to 3000 rpm..wich is too much for that little throttle pedal press...
 
Apr 12, 2008
539
1
This morning car started ok, on vag com block 061 throttle drive angle sensor is at 0 while idiling
then, after 10 minutes of idiling, my idle went bad again, got code

17705 - Pressure Drop between Turbo and Throttle Valve (check D.V.!)
P1297 - 35-00 -

When it idles bad, on block 061 throttle drive angle sensor is at 1.6, 2 %...not 0 as before when car was idiling ok..
Maybe throttle pedal problem?
And, when it idles ok it is easy to slowly increase rpm, but now it is very hard, if i press throttle pedal just a little bit, rpm goes to 3000...
 

mattyholmz89

Active Member
Feb 8, 2011
453
0
Huddersfield
Can I ask how bad your idle was? Mine is running rough on idle and upto around half throttle... if I put my foot down it feels fine and boosts hard just idle uneven and dips every 5-10 seconds sometimes worse than others... gonna clean throttle body see if that works just wondering what yours was like on idle?
 
Apr 12, 2008
539
1
My vac was on -0.6 bar, sometimes -0.4, even -0.3 instead of -0.8, -0.9...idle was lumpy and u could really feel smell of unburned fuel through exhaust..
While idle was bad, u could hear loud sucking noise through cone filter..
 
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