Wierd firing when hot issue

[shivadow]

So.. This engine is aum yet on the reg looking for parts its an arx.

It does this least when hot but when it does do it hot its more severe and stalls the engine. Always hunting revs even when holding throttle at 1k (throttle response is over active likes to go straight to 1.5k, no messing about.

Battery power is 13.5-13.9 volts. Bottom end of the recommended but should be ok as all electricals are off when running.

Stft fluctuates mostly +, sometimes double figures, but has suddenly gone major - and riched itself to stall. + Indicates leaning out, vacuum leak or injectors, lack of fuel. Ratio fluctuates 14.6.1 - 14.9.1 indicating fuel trim working to compensate?.. Makes sense.. But why?.

LTFT, doesn't budge from 0.8. No matter what. Even after revving at 3k for 10 mins or so.

Vac leak test around engine bay with carefully planned butane enrichment with no resulting change to condition. Quite sure vac is tight. Vac at turbo is a healthy -11/11.5. No problems spooling.

Injectors, I've tried the "long screwdriver" method to check for ticking but cant hear sod all. Maybe I'm going deaf. The plastic collars around them seem to have oil on them but cannot tell yet if it's actually from the collars. From what I've read it's normal. No smells of fuel. Fuel pressure seems good.

Ecu, as we know this is a common issue on all cars that manufacturers decided to put electronic masterpieces under a poor mans waterfall. The windcreen. Maybe water ingress has made the ecu angry and a replacement may be necessary. Check engine light appears and disappears at whim, no codes stored, cel resets itself if turned off then on, losing codes?. Last codes were tps and adaption (limp mode). Cleared itself.

Suspect injector open/close issue. Could be an egomanic ecu.

Any thoughts?

Edited 5 November, 2015 by shivadow

[shivadow]

Well it dawned on me that if I'm going to check the injectors what harm can a can of fuel system cleaner do..

Run it till hot, added an entire can of "clean drive" fuel additive to just under half a tank of choo choo juice and run it for 10 minutes at idle then 10miles. ltft is now permanently 0.0 and stft is now +0.8/-0.8 and fluctuating rarely except when throttle is applied.

DBW system now communicates at the correct angles, it no longer wants to jump to 1.5krpm immediately.

Idle is smooth, end of. Not just smoother but it seems to be sorted.

Fuel usage is now reasonably good.

Engine starts and runs faster and quieter.

Theory behind this..

When the engine is switched off the petrol in the end of the injector evaporates instead of burning. This leaves an oily/waxy residue that builds up over time. A good fuel additive with acetone and xylene (both potent paint and skin strippers) should help dissolve the oily/waxy residue and burn it off in the cylinder.

In my case I believe that the injectors were half clogged, they have 5 nozzles each, and the fuel was being pressurised within the injector because of the blockage and then spurting out late and missing the spark, explaining the fuel rich exhaust gasses. The knock on effect is the sensors telling the engine something isn't right so it adjusts stft until out of range which in turn activates ltft, which is not needed and causes over fuelling.

My test phase is not complete yet but anyone who is experiencing firing issues should try fuel additive first.

You're welcome...

Edited 6 November, 2015 by shivadow

[Liverpool-Lad]

Interesting, so what additive did you use?  How many miles has the engine done?

[shivadow]

Just under 97k and it was called "drive clean". Green and silver metal bottle. It still hasnt blipped since. I am gobsmacked by the difference it has made.

[Liverpool-Lad]

Madness.  Ive done the same miles as you.  I do try and feed it Tesco 99 or V Power though, so perhaps thats helping.

[shivadow]

I used to use tesco fuel then moved to shell vpower but the symptoms got worse. The fuel isn't the issue as such, "fuel varnishing" was probably the issue as this is day 3 of faultless starts.

The buildup of crud from fuel is a byproduct of fuel itself. I must stress that the active ingredients in the product i used were acetone and xylene. There are products out there that don't contain those chemicals so choose wisely.

All fuels sold in this country are to an iso standard so "bad fuel" is just a myth that started when tesco tried to skimp on profits about 10 years ago and sold a bad batch of mechanical horse feed which poisoned everones horses. I think that turned out to be a fault with fuel filters in the long run.. Anyway, I digress..

Just try it and if you have an obd2 scanner see what the codes are and watch your fuel trims!.

[shivadow]

Well, the plot thickens..

Car has been running great for its usual 200 miles then all of a sudden out of the blue the ba****d starts hunting for revs for no reason. Only dropping, not gaining revs. As in it wont rev over idling on its own but will try to die and save itself.

There is no misfire, no smell of petrol at the exhaust, not lumpy running.

So i stamp on the pedal and rev it up to 6k for about 10 seconds, drop it to 3k for ten seconds and let off completely. Car idles normal again. Hunting stopped.

This is very puzzling now.

I have vcds and a cable. No dtcs stored past or present relating to the engine. I have a climatronic issue, airbag voltage issue and drivers door lock and the door behind that (right hand side).

At this point my laptop run out of power so i had to stop until later. This is what I have so far..

Tuesday,10,November,2015,13:39:46:33490

VCDS -- Windows Based VAG/VAS Emulator

VCDS Version: 12.12.3.0

Data version: 20140905

VIN: TMBSL21U4xxxxxxxx License Plate: NA02NWP

Mileage: 155880km-96863mi Repair Order:

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

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

Chassis Type: 1U (1U - Skoda Octavia (1997 > 2011))

Scan: 01 02 03 08 15 16 17 19 22 29 35 36 37 39 46 56 76

VIN: TMBSL21U4xxxxxxxx Mileage: 155880km/96859miles

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

Address 01: Engine Labels: 06A-906-032-AUM.lbl

Part No: 06A 906 032 SG

Component: 1.8L R4/5VT 0010

Coding: 10700

Shop #: WSC 20028

VCID: 75E7978F4F43E4B6B8B-5000

TMBSL21U4xxxxxxxx SKZ7Z0A1xxxxxx

1 Fault Found:

16804 - Catalyst System; Bank 1

P0420 - 35-00 - Efficiency Below Threshold

Readiness: 0000 0000

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

Address 03: ABS Brakes Labels: 1C0-907-37x-ESP-A.lbl

Part No: 1C0 907 379 F

Component: ESP ALLRAD MK60 0104

Coding: 0023174

Shop #: WSC 31480 000 00000

VCID: 2D577FEFB793EC7600B-5000

No fault code found.

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

Address 08: Auto HVAC Labels: 1Ux-907-044.lbl

Part No: 1U1 907 044 A

Component: CLIMATRONIC C 2.0.0

Coding: 11000

Shop #: WSC 31480

VCID: 3069669BF0A1819E2BD-5072

2 Faults Found:

00792 - A/C Pressure Switch (F129)

35-00 - -

00281 - Vehicle Speed Sensor (G68)

37-10 - Faulty - Intermittent

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

Address 15: Airbags Labels: 6Q0-909-605-VW5.lbl

Part No: 1C0 909 605

Component: 0L AIRBAG VW51 0B 0004

Coding: 12364

Shop #: WSC 31480

VCID: E1CF53DF6BCBF816743-5000

1 Fault Found:

00532 - Supply Voltage B+

07-10 - Signal too Low - Intermittent

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

Address 17: Instruments Labels: 1U0-920-xxx-17.lbl

Part No: 1U0 920 911 B

Component: KOMBI+WEGFAHRSP VDO V07

Coding: 23412

Shop #: WSC 25043

VCID: 2E5578E3EA95976E391-5000

TMBSL21U4xxxxxxxx SKZ7Z0A1xxxxxx

1 Fault Found:

01304 - Radio

49-00 - No Communications

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

Address 19: CAN Gateway Labels: 6N0-909-901-19.lbl

Part No: 6N0 909 901

Component: Gateway K<->CAN 0001

Coding: 00006

Shop #: WSC 31480

VCID: F0E9269BB021419EEBD-5000

1 Fault Found:

01304 - Radio

49-00 - No Communications

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

Address 22: AWD Labels: 02D-900-554.lbl

Part No: 02D 900 554 C

Component: HALDEX LSC ECC 0010

VCID: 204996DBA041311EBBD-4A9C

No fault code found.

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

Address 46: Central Conv. Labels: 1C0-959-799.lbl

Part No: 1C0 959 799 B

Component: 3Y Komfortgerát HLO 0003

Coding: 00259

Shop #: WSC 31480

VCID: 3665508312C5AFAE711-4A9C

Subsystem 1 - Part No: 1U6959802D

Component: 3Y Tõrsteuer.FS KLO 0004

Subsystem 2 - Part No: 1U6959801D

Component: 3Y Tõrsteuer.BF KLO 0004

Subsystem 3 - Part No: 1U0959811D

Component: 3Y Tõrsteuer.HL KLO 0002

Subsystem 4 - Part No: 1U0959812D

Component: 3Y Tõrsteuer.HR KLO 0004

2 Faults Found:

00928 - Locking Module for Central Locking; Front Driver Side (F220)

27-00 - Implausible Signal

00931 - Locking Module for Central Locking; Rear Right (F223)

27-00 - Implausible Signal

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

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

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

Readiness Status: 0000 0000

Exhaust Gas Recirculation: Passed

Oxygen Sensor Heating: Passed

Oxygen Sensor(s): Passed

Air Conditioning: Passed

Seconday Air Injection: Passed

Evaporative Emissions: Passed

Catalyst Heating: Passed

Catalytic Converter(s): Passed

If anyone in the Liverpool area needs a scan just let me know and we will arrange something. I'll scan and send the results to an email of your choice, dtcs will only be cleared at request. Please note that it'll be £20 cash for leccy and time as you'll be travelling to me.

Edited 10 November, 2015 by shivadow

[kentphil1]

That is quite an old VCDS version that you are running, we are now on 15.7.1, have you not updated yet for newer label files?.

[shivadow]

Nope didn't want to chance it not working while i needed it. It did offer to update but as i only had the cable for 5 minutes any readout is better than none. I'll update and run it again but i doubt the vcds version makes a difference seeing as the car is so old.

Update : so i updated to 15.7 and it needs the cable eeprom updating to 1.94. Currently my cable is 1.93 and fails to update rendering the app useless.

All this hassle with some crappy old skoda and i plan on getting an rs6.. I must be touched in the head.

But enough about that. Can that error for vehicle speed sensor be causing my issues?

Edited 10 November, 2015 by shivadow

[kentphil1]

I find the latest version very stable, and some of the drop down boxes have changed format slightly which makes life easier, but your decision at the end of the day.

[shivadow]

Due to the lack of abundance in help and knowledge on all fronts, not being able find a single mechanic that has a clue what a car is, it's up for sale. No sale = scrapped.

Ebay Item number:281853591619.

[YellowCar]

Sorry to hear that, also sorry to hear that 3 pages of thread doesn't constitute people trying to help...