Misfire problems in cng mode only

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pavkata882
Beiträge: 3
Registriert: 14.06.2019 11:05

Misfire problems in cng mode only

Beitrag von pavkata882 » 18.06.2019 15:06

Hello everyone and sorry for typing in english, but my german language skills won't be enough to describe the problem that I have.
The car is a VW Passat B7 with the CDGA 1.4 ecofuel engine. So the problem that I have is basically this - when the engine warms up it starts misfiring at idle and after a while the check engine starts flashing and the car switches to petrol mode and the misfiring stops. The problem has been around for the past week and I kinda explored it and found a way to deal with it(sort of). I found out that it only misfires on idle and when the throttle is lightly pressed, but when accelerating, the misfire is gone and the engine stops jerking.
According to VCDS, the fault code is only a random misfire detected during nat. gas operation. I am wondering if any of you has had this problem in the past and/or if possibly knows what the cause is.
I probably forgot to mention some details, so if you need anything else as information just ask and I'll try to provide it asap. Thanks in advance!

MiniDisc
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Re: Misfire problems in cng mode only

Beitrag von MiniDisc » 18.06.2019 16:28

Hello pavkata882,

please check the spark Plugs .... exact model, age and used milleage. Problems with spark Plugs starting in CNG Mode earlier.

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Sven2
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Re: Misfire problems in cng mode only

Beitrag von Sven2 » 18.06.2019 17:00

According to my garage the exchange interval of 60,000 km is the absolute maximum possible. I reported some misfire in CNG mode on my Touran (same engine) a few weeks before the 60,000 km inspection. Problem had been solved by exchanging of the spark plugs.
If the spark plugs are OK:
An other common flaw on these engine are damaged ignition coils. If misfire is always on the same cylinder: Permute the ignition coil on the cylinder with misfire with one form an other cylinder. If the misfire follows the ignition coil: Exchange this part.

good luck
Wiederholungstäter: früher Touran TSI_EF, jetzt B200 NGD

pavkata882
Beiträge: 3
Registriert: 14.06.2019 11:05

Re: Misfire problems in cng mode only

Beitrag von pavkata882 » 18.06.2019 17:24

Coil packs and spark plugs are okay, I'm actually wondering if it could be an injector. The car already has 192 000km on the clock and none of the injectors have been replaced yet, but they are kinda pricey so I can't just install them and hope for the best, this is why i wanted to ask first.

MiniDisc
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Registriert: 10.03.2012 19:00
Wohnort: Sachsen

Re: Misfire problems in cng mode only

Beitrag von MiniDisc » 18.06.2019 19:43

MiniDisc hat geschrieben:
18.06.2019 16:28
Hello pavkata882,
please check the spark Plugs .... exact model, age and used milleage. Problems with spark Plugs starting in CNG Mode earlier.
pavkata882 hat geschrieben:
18.06.2019 17:24
Coil packs and spark plugs are okay
"Okay" is not an helpful answer to the questions, what do you expect? :arab:

pavkata882
Beiträge: 3
Registriert: 14.06.2019 11:05

Re: Misfire problems in cng mode only

Beitrag von pavkata882 » 18.06.2019 21:01

Spark plugs have been changed in less than 5000km and I already tried the coil pack swap methode, but the misfire still goes in cylinder 1.

PowerPoldi
Beiträge: 77
Registriert: 06.02.2017 21:17

Re: Misfire problems in cng mode only

Beitrag von PowerPoldi » 19.06.2019 09:36

Did you check the electrical connection on the CNG-Valve of cylinder 1?

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