Misfire on 1.4Tsi 118kw (only on cyl1&4 during accelerator pedal release)

DA

I'm just starting to monitor misfires counter on cyl 1-2-3-4 with VCDS....on my Golf Mk6 1.4Tsi 118kw DSG 7speeds.

Avg on 35km trip morning, I can have about 2-3 misfires.

From all misfire events occurred..

1) Baaed on which cylinder the misfires occurred :
Cyl 1 = 60% probability
Cyl 4 = 30% probability
Cyl 2 = 9% probability
Cyl 3 = 1% probability....I'm just making up the figure....but yes...almost never happens in cyl3.

I tried to swap the coils....1 with 3 and 2 with 4. ....still the same >> misfires mostly on cyl 1&4.

2) Based on engjne load/TPS :

60% misfires occurs during stop&go/crawling at gear 1-2 between 800-1800rpm and speed under 15mph/24kmh (espcially during the release of the accelerator pedal after a light pressure on....come on it's stop on go, how hard can you press).

35% misfires occurs on the highway (speed about 40-60mph/65-95kmh...also after releasing the accelerator pedal after light accelaration or even steady cruise).

5% i would say happens during flat-out acceleration >>> but ONLY HAPPENS if i plug-in the racechip.

My record was 17 misses in cyl4 after flat-out with chip at 4500++rpm in 2nd gear...then engine started to loss power & rattling (looks like i lost power from 1 or 2 cyl). Everything back to normal after engine shutdown & unplug the chip (guess it will be normal too without unpluging the chip....if you give about 20-30min cooldown).

It used to be okay flatting-out with racechip then something happened after I cameback from abroad (I left the car on open yard) for 6 days....i saw rat drops on engine, but could not find which cable they bite.

Flatting the pedals without the racechip are still fine up to now.

Other notes :
I saw Fuel Adaptation (PARTIAL) on VCDS once deviates below -20% for 6 seconds on July 20th....after released of accelerator pedal during cruising 3300rpm stable speed in 5th gear & lambda actual was between 0.97-1.03.


Then I used Amsoil PI
1st bottle with 4:1 dosage (5 gals fuel)
2nd bottle with 2.5 :1 dosage (8 gals fuel)
3rd bottle with 1.5:1 dosage (13 gals fuel)

Seems improving the Fuel Adaptation Partial values....never saw any numbers below -10% again.

But misfires on cyl 1&4 are still occurs (even NO RACECHIP PLUGGED-IN) although its decreasing from 2-3 misses on 35km morning trip....to 1-2 miss (sometimes 1 miss only)

With racechip on (now I am plugging it in again after cleaning the injectors with 3 bottle's Amsoil PI)..... I am having more misfires with normal drive.

Haven't tried flatting out the accelerator again....I am still adapting the engine (to avoid having 17 mises in a row & losing 1-2 cyls at a sudden like last month)

Can anybody explain :

1) Why misfires espcially during the release of the accelerator pedal after a light pressure on it ? In my case since traffic is bad....occurs during pedal release in stop&go/crawling... 800-1800rpm gear 1-2 ....below speed 15mph/24kmh

2) Full throttle are fine without anychip....almost never has misfires with throttle on.
With racechip...full throttle over 4500++rpm...I experienced 17mis in a row on cyl4.....which I though due to dirty injectors (my reading of Fuel Adaptation Partial was not good at that time....and improved after 3 bottles Amsoil PI).
Is this misfires with racechip at full throttle high rpm....really due to dirty injectors?

Any advices & opinions will be greatly appreciated
Thanks in advance

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Ok, i have considerable experience with this engine, including tuning....

For the 'throttle release' occasional logged misfire - this is normal for this engine, they all do it.

Its a bug in the ecu software whereby it doesn't deactivate the misfire detection fast enough upon throttle release and sometimes it will log a single random misfire. When you release the throttle the misfire detection is supposed to be disabled immediately (as its normal for a misfire when fuel is cut upon throttle release). However high speed logging shows that sometimes the detection is not disabled fast enough and it will log a misfire.

This engine's ecu software is full of bugs/quirks by the way - i have documented numerous ones over the years on different forums (such as the cat preheating only occurring on startup if the coolant temp is between 20 & 30c)

The full throttle misfires with the racechip however are real. There are numerous possible reasons for this:

Spark gap too wide
Make sure you are using the latest iridium tip sparks, VW part 03C905601B or NKG SIZFR6B8EG) Stock gap is 0.8mm - but usually they come out of the box at 0.75, you may want to try experimenting dropping the gap to 0.7mm.

Fitting NGK BKR7EIX is also an option (although they are a heat range colder and also slightly shorter...revo recommend them but my experiments show they coke up a bit too easily if you drive normally for a while, also idle is more lumpy as the don't perform as well at low RPM/load due to sitting higher up in the cylinder head)

Running too rich
This is a common problem with many a tune for this engine (especially APR). In order to protect the engine the map run's rich under heavy load - however the ECU has a built in protection system on top of this whereby if EGT's exceed a limit it will significantly run richer.

I have found the misfires occuring under full throttle - at the 4.5K rpm mark have occurred right when this EGT safety mechanism has kicked in and AFR drops to as low as 10 (very rich) - it is then the misfires occur.

The problem is EGT is a calculated value, it's not directly measured and the ECU calculates it from AFR and other variables - but when EGT protection kicks in, with a map that's already set to rich under full load/throttle, the result can just be too rich a fuel mixture to ensure an ignition.

The solution is to change tune or go stage 2 - where the maps usually don't usually run so rich as they are expecting lower EGT due to the turbo back exhaust.

Also ensuring the sparks are in the best possible setup for ignition can sometimes tip you back to the right side of that misfire edge.

Other causes include a stretched timing chain, burnt exhaust valves, fuel delivery issues (hp or lp fuel pump) etc

Interesting info about the misfires counter bug. Ive made topics before about the strange random low misfire counts at low RPM when cruising with light on/off throttle input on the 2.0 TSI and others reported the same phenomena when monitoring their cars with VCDS. I never had any drivability issues or misfires at high RPM or in boost.

blower said:

Ok, i have considerable experience with this engine, including tuning....

For the 'throttle release' occasional logged misfire - this is normal for this engine, they all do it.

Its a bug in the ecu software whereby it doesn't deactivate the misfire detection fast enough upon throttle release and sometimes it will log a single random misfire. When you release the throttle the misfire detection is supposed to be disabled immediately (as its normal for a misfire when fuel is cut upon throttle release). However high speed logging shows that sometimes the detection is not disabled fast enough and it will log a misfire.

This engine's ecu software is full of bugs/quirks by the way - i have documented numerous ones over the years on different forums (such as the cat preheating only occurring on startup if the coolant temp is between 20 & 30c)

The full throttle misfires with the racechip however are real. There are numerous possible reasons for this:

Spark gap too wide
Make sure you are using the latest iridium tip sparks, VW part 03C905601B or NKG SIZFR6B8EG) Stock gap is 0.8mm - but usually they come out of the box at 0.75, you may want to try experimenting dropping the gap to 0.7mm.

Fitting NGK BKR7EIX is also an option (although they are a heat range colder and also slightly shorter...revo recommend them but my experiments show they coke up a bit too easily if you drive normally for a while, also idle is more lumpy as the don't perform as well at low RPM/load due to sitting higher up in the cylinder head)

Running too rich
This is a common problem with many a tune for this engine (especially APR). In order to protect the engine the map run's rich under heavy load - however the ECU has a built in protection system on top of this whereby if EGT's exceed a limit it will significantly run richer.

I have found the misfires occuring under full throttle - at the 4.5K rpm mark have occurred right when this EGT safety mechanism has kicked in and AFR drops to as low as 10 (very rich) - it is then the misfires occur.

The problem is EGT is a calculated value, it's not directly measured and the ECU calculates it from AFR and other variables - but when EGT protection kicks in, with a map that's already set to rich under full load/throttle, the result can just be too rich a fuel mixture to ensure an ignition.

The solution is to change tune or go stage 2 - where the maps usually don't usually run so rich as they are expecting lower EGT due to the turbo back exhaust.

Also ensuring the sparks are in the best possible setup for ignition can sometimes tip you back to the right side of that misfire edge.

Other causes include a stretched timing chain, burnt exhaust valves, fuel delivery issues (hp or lp fuel pump) etc

Click to expand...

Hi Blower,

It has been quite a while since you helped me with my previous post about DIY intake valves cleaning on this engine [emoji1].

Nice to hear from you again and thank you for all knowledge you have shared.

For the misfires logged during throttle release...I will close my eyes....and try to focus on the full throttle misfires with the racechip on (no misfires on full throttle if I take out the racechip).

I have plugged in the racechip for about a year (since milage : 26,000miles/42,000km) & quite pleased for what I have got for EUR129....I feel noticible power increment from the chip...but sometimes feels lumpy during first start up in the morning.
Current car's milage is 33,000miles/53,000km

So after a while I changed :
Fuel Filters
Spark Plugs BKR6EIX
Red ignition coils 115E
Fuel is always 98 octane

After changing those items....morning lumpiness gone and idle feels even smoother.

Only occasionally I got G71 implausible signal (mostly in the morning at first start or after car has been sitting for 6++ hours....more often in the morning 5.30am before taking the kids to school).
But this G71 might disappears after car sits over 3-4 houra

Actually the full throttle misfires started after I got back from abroad (left the car in open area for 6 days...and I saw some rat drops....they chew my negative battery cable's jacket ...eventhough ignition wires and other wires seems fine).

Since then the full throttle misfires (with chip on) begins.

Therefore...I suspected some possibilities of this chip-on misfires were caused by some hidden wires got bitten (unstable electricity under full load over 4500rpm).

Regarding your notes of running too rich / too wide gap / stretched timing chain :

This morning I gathered some data for this full load chip-on misfires....it happens mostly on cyl-1 or cyl-4 or both ...when :
- full throttle
- begins when rev over 4000rpm and torque over/nearly 200Nm.

I made the table :
- yellow shade rows are the times when i accelerate full throttle
- red cells are when it touch 4000++rpm or torque 200++Nm or when misfires count 5++
- but lambda is not even lower than 0.9 (AFR still about 13?)



Is it still EGT calculation?

But anyway ...as your suggestions of the plugs....soon I am going to change plugs to 03C905601B (hope they are availble in my country)...or I can try to buy NGK SIZFR6B8EG.

They have BKR7EIX here....but I still prefer 03C905601B or SIZFR6B8EG

For the other cause of stretched timing chain.....can it be checked from VCDS?
I read some Audis/VWs can be checked in VCDS.

Many thanks for your help.

Regards

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