Misfire no CEL no Codes

[jrpug407]

Hi all

I have a Jetta (2012) 1.4tsi CAVD currently clocking 189000km. A bit of info before I get to the issue this car had an engine and transmission replacement at 75000km under warranty according to the dealership it's an updated version of the engine, but now that the warranty is well over the misfires from my obd2 scan is giving me the jitters.

All started with a usual cold vibration, so I used the obd 2 Wi-Fi scan tool to scan the engine, results shown several counts of misfire in cylinder 1. No Check engine light No trouble codes either.

Suspecting it could be bad coils or plugs I switch them around I found that spark plug in cylinder 1 had black soot on it and the tip looked a little bent and so I changed it with a new piece. I ran the scan code again and cylinder 1 still shows 5 counts of misfire still no check engine light nor fault codes.

I do know the the car is not running as it should for at times it's really smooth and sometimes it's rough when it idles too there's intermittent vibrations and when accelerating it's feels like its pulling back.

Next was to bring over to a garage they too were surprised that their scan tool didn't pick up any misfire, so proceeded with a compression test and results were 12 bars (170psi) across all 4 cylinders. At a lost they decided to change connectors to the coil packs as the plastic clip were broken. After all that I ran obd 2 again and still shows cylinder 1 misfire and still no check engine light and no fault codes though my fuel consumption has deteriorated and cold start vibrations are still bad.

I would appreciate any advice given to resolve this mysterious misfires thanks

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[tyr382]

What’s your fuel trims at?


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[jrpug407]

Hi there tyr382 thanks for asking I have managed to copy some of the test results pretty long though.

Mode $01 - Powertrain Diagnostic Data

PIDDescriptionValueUnits
SAE 0x03Fuel system 1 status2
SAE 0x03Fuel system 2 status0
SAE 0x04Calculated load value12.94%
SAE 0x05Engine coolant temperature87C
SAE 0x06Short term fuel % trim - Bank 13.12%
SAE 0x07Long term fuel % trim - Bank 1-2.34%
SAE 0x0BIntake manifold absolute pressure4.35psi
SAE 0x0CEngine RPM868.5RPM
SAE 0x0DVehicle speed0km/h
SAE 0x0EIgnition timing advance for #1 cylinder0deg
SAE 0x0FIntake air temperature48C
SAE 0x11Absolute throttle position12.16%
SAE 0x13Location of oxygen sensors3
SAE 0x15O2 voltage (Bank 1, Sensor 2)0.46V
SAE 0x15Short term fuel trim (Bank 1, Sensor 2)99.22%
SAE 0x1COBD requirements to which vehicle or engine is certified6
SAE 0x1FTime since engine start473sec
SAE 0x21Distance traveled while MIL is activated0km
SAE 0x23Fuel rail pressure709.23psi
SAE 0x2ECommanded evaporative purge32.94%
SAE 0x30Number of warm-ups since DTCs cleared17
SAE 0x31Distance traveled since DTCs cleared198km
SAE 0x33Barometric pressure14.5psi
SAE 0x34O2 sensor lambda wide range (current probe) (Bank 1, Sensor 1)1
SAE 0x34O2 sensor current wide range (Bank 1, Sensor 1)-0.02mA
SAE 0x3CCatalyst temperature (Bank 1 Sensor 1)274.8C
SAE 0x42Control module voltage13.59V
SAE 0x43Absolute load value18.82%
SAE 0x44Fuel/Air commanded equivalence ratio1
SAE 0x45Relative throttle position1.96%
SAE 0x46Ambient air temperature39C
SAE 0x47Absolute throttle position B12.16%
SAE 0x49Accelerator pedal position D14.9%
SAE 0x4AAccelerator pedal position E14.9%
SAE 0x4CCommanded throttle actuator control2.35%
Aux 0x00Input voltage read by the scan tool13.3V

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[VR28LT]

Sounds like excessive carbon build up

[Lucas_R]

Could very likely be carbon buildup on your injectors causing the misfire with those km's.

When VW replaced your engine they would have reused the injectors from your old engine (as well as alternator/starter motor/ac compressor etc) so the injectors have done 189,000km.

Fuel System Cleaner/Conditioner | Supercheap Auto

Fuel Injection Cleaner - 300mL | Supercheap Auto

[tyr382]

Hard to say looking at your data at idle.
Your ST is pretty lean but your LT is ok but is in the enrich condition.
Your intake temp is fairly high that could mean carbon build up so I wouldn’t doubt that buildup is the issue.

Another potential issue can be faulty coil pack.
I say do as much as you can to isolate the issue, swap he coil packs from each cylinder and see if the misfire changes position.

Also take it for a drive and watch your LT fuel trims.
Wouldn’t hurt putting in some injector cleaner aswell


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[The_Hawk]

I looked into this a long while back and it seems that it's 'normal' that there is a pretty low number, pretty evenly spread across all the cylinders when you look at the computer.

118TSI Misfire Count

When the engine went bang in 2017 the faulty cylinder did start misfiring constantly and the total numbers went up massively for that one, all the rest were normal. That caused a CEL, but the 'normal' nunmber apparently is OK.

Even after a rebuild it still happily misfires and is up to a few hundred on each. I've considered the R8 coil packs and adaptor for a stronger spark, but I'm not sure even that would fix it, apparently the injector blows fuel in such a way that it's possible to damp the spark too much, apparently it was moved (??) in the CTHD... and even that engine disappeared if that's telling enough for you.

[jrpug407]

Guys,

Thanks a bunch for all the feedback very useful indeed. Sorry I took sometime to post a reply as I was stuck in the garage half a day.

As many of you had pointed out carbon build up could be the culprit here. The guys at the garage did a decarbonization job. It seems to be running a bit better now though obd 2 scan still shows a few misfire counts.

here are the results of obd 2 after decarbonizing apologies for all the clutter

Test report:
------------------
MID:$01 TID:$83
- O2 Bank 1 Sensor 1
Max: 1.92888 Min: 1.99644
Test result value: 0.85125
FAIL
----
MID:$02 TID:$81
- O2 Bank 1 Sensor 2
Max: 0.65002V Min: 0.65978V
Test result value: 0.64026V
FAIL
----
MID:$21 TID:$84
- Catalyst Monitor Bank 1
Test incomplete or dependant test failed
--
MID:$35 TID:$81
-
Max: -20° Min: -19.61°
Test result value: -19.61°
FAIL
----
MID:$3d TID:$8b
- EVAP Monitor (0.020")
Test incomplete or dependant test failed
--
MID:$41 TID:$85
- O2 Heater Monitor Bank 1 - Sensor 1
Max: 1,302.80005°C Min: 759.90002°C
Test result value: 819.90002°C
PASS
----
MID:$42 TID:$81
- O2 Heater Monitor Bank 1 - Sensor 2
Max: 918Ohm Min: 0Ohm
Test result value: 124Ohm
PASS
----
MID:$a2 TID:$0b
EWMA Misfire counts (average) for last 10 drive cycles - Misfire Cylinder 1 Data
Max: 65,535Count Min: 0Count
Test result value: 29Count
PASS
----
MID:$a2 TID:$0c
Misfire counts for last/current driving cycles(calculated) - Misfire Cylinder 1 Data
Max: 65,535Count Min: 0Count
Test result value: 0Count
PASS
----
MID:$a3 TID:$0b
EWMA Misfire counts (average) for last 10 drive cycles - Misfire Cylinder 2 Data
Max: 65,535Count Min: 0Count
Test result value: 0Count
PASS
----
MID:$a3 TID:$0c
Misfire counts for last/current driving cycles(calculated) - Misfire Cylinder 2 Data
Max: 65,535Count Min: 0Count
Test result value: 1Count
PASS
----
MID:$a4 TID:$0b
EWMA Misfire counts (average) for last 10 drive cycles - Misfire Cylinder 3 Data
Max: 65,535Count Min: 0Count
Test result value: 1Count
PASS
----
MID:$a4 TID:$0c
Misfire counts for last/current driving cycles(calculated) - Misfire Cylinder 3 Data
Max: 65,535Count Min: 0Count
Test result value: 3Count
PASS
----
MID:$a5 TID:$0b
EWMA Misfire counts (average) for last 10 drive cycles - Misfire Cylinder 4 Data
Max: 65,535Count Min: 0Count
Test result value: 0Count
PASS
----
MID:$a5 TID:$0c
Misfire counts for last/current driving cycles(calculated) - Misfire Cylinder 4 Data
Max: 65,535Count Min: 0Count
Test result value: 0Count
PASS
----


End of report.


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[jrpug407]

I looked into this a long while back and it seems that it's 'normal' that there is a pretty low number, pretty evenly spread across all the cylinders when you look at the computer.

118TSI Misfire Count

When the engine went bang in 2017 the faulty cylinder did start misfiring constantly and the total numbers went up massively for that one, all the rest were normal. That caused a CEL, but the 'normal' nunmber apparently is OK.

Even after a rebuild it still happily misfires and is up to a few hundred on each. I've considered the R8 coil packs and adaptor for a stronger spark, but I'm not sure even that would fix it, apparently the injector blows fuel in such a way that it's possible to damp the spark too much, apparently it was moved (??) in the CTHD... and even that engine disappeared if that's telling enough for you.

Hawk

Thanks for sharing your thread on the misfires looks like it's common issue with the direct injection tsi engines.

I wondering if the CTHD and CAVD share the same injector placement thus like you had mentioned causing spark plugs to get damped?

If so it I'm wondering did it take so long to show up on OBD ? or perhaps the misfires always been there from the beginning?

Do you suppose in my case could it be a sign of a failing cylinder? My compression test does fall in the normal range though. Appreciate your thoughts many thanks

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[The_Hawk]

My misfires were all very even, when the piston cracked it suddenly ran like a bag of **** and the misfires on that one cylinder instantly skyrocketed. I think they have likley been there all along and are probably not reflective of an impending failure.

Even now following a rebuild and those numbers reset to zero they are slowly growing across all the cylinders.

Your stats seem to be reading a different value to mine (although note that I'm seeing them on the MFD using a PolarFIS), but I get instant misfires on one screen (which is misfires in the last 30 seconds or something like that, so it will show 1 then go back to zero) or total misfires (total number for all time) on another.

You're seeing averages, so they may move up and down, although there are plenty of zero's there... I doubt any of my would be.

What are you reading those with? It would be interesting to drag out my VCDS cable and see what mine are as a comparisson.