Intermittent misfire

[Norecs]

Hi!

 

I'm struggling with a really intermittent misfiring issue and thought you guys might have some advice.

Vehicle is a 2013 Octavia 1.4TSI 7DSG with 177 000km.

 

6 months ago, when backing up to my parking spot and setting to park, the check engine light started flashing and the engine started vibrating. After shutting it down and starting up again, the light was off and everything seemed to be fine. Some weeks later i had VCDS hooked up and it reported cylinder 3 and 2 intermittent misfire (P0303 and P0302) with a timestamp pointing at the time i had the problem.

Cleared the codes.

 

Up until yesterday, everything had been fine, until again, i backed up to a parking spot (not sure if coincidence?), stopped, and the CEL started flashing. Restarting the car "fixed" the problem but VCDS reports cylinder 1 and 4 intermittent misfire P0301 and P0304 (note that 6 months ago it was 2 and 3) at the time CEL was flashing.

 

Both times the issue occurred - the car had reached operating temperature, AC running. As i think of it, ever since i bought the car 8 months ago, the idle has felt a little rough once the engine has warmed up but i'm not sure if i'm imagining it or not. Could it be that there's minor misfirings happening all the time and it only becomes apparent when idling?

I've never felt any hesitation or issues when accelerating or while the vehicle is moving at any speed though.

 

In-between the 2 misfiring occasions, all the spark plugs have been replaced along with the air filter at a reputable place (not sure if they switched coil positions while doing it or not). I have done some googling and im guessing I should swap around the coil packs to see if the misfire reports at different cylinders but doing so, I may need to wait several months if not more, for the results and I can't really trust the car anymore on long trips...

 

Is there anything else that I can do/check in the driveway without any special tools, without taking the car to a repair shop? Any ideas?

Or order and replace all 4 coils just to be sure? Costly if it's not the coils causing the problem though.

[MoggyTech]

Coil packs tend to fail and cause a dead cylinder, However, the coil pack boots can crack and then you do get misfires. The VCDS evidence suggest coil pack 3 and 2 are faulty, and were probably swapped to different cylinders when the plugs were replaced. 

The packs are also notoriously hard to remove even with the correct tool. I would remove them (using proper tool) and inspect the packs for signs of damage.

Replacing them all is the safest (if not the cheapest) option.

[Plantman]

Agreed, I had my spark plugs replaced recently and the mech said they are a nightmare to remove without damaging the boots. The only decent way is to get the engine and components really hot which makes it easier.

 

Certainly getting a coil pack(s) to test/replace.  If they are originals they have done pretty well. We had to replace ones on our Fabia at only 35k but the car is a 2012.

 

 

[Norecs]

Thanks for the replies. This encouraged me to order 4 new Bosch coils. They should arrive within a week, I'll update on the results once I have changed them. Fingers crossed.

 

During the winter period, I also had an issue when outside temperature was around 0C (32F) or less, the car would not warm up when idling. If I drive around it gets warm really fast but when stopping at a light or anywhere really, the coolant loses temperature about 10 degrees C per minute - noticeably the needle drops. I took it in for diagnostics and no issues were found with thermostats. Could this also be related to the misfiring issue?

[indars]

On 22/04/2019 at 21:20, MoggyTech said:

Coil packs tend to fail and cause a dead cylinder, However, the coil pack boots can crack and then you do get misfires. The VCDS evidence suggest coil pack 3 and 2 are faulty, and were probably swapped to different cylinders when the plugs were replaced. 

The packs are also notoriously hard to remove even with the correct tool. I would remove them (using proper tool) and inspect the packs for signs of damage.

Replacing them all is the safest (if not the cheapest) option.

Guys in Russian forums advice to remove coil packs on warm (hot?) engine- then it’s easy. But will not have possibility to check this since just bought Octy 2.0TDI instead of 1.4TSI (about what was dreaming last 2 years :-/

[Norecs]

Sorry for disappearing for a while.

A little update:

 

I have replaced coils 1 and 2.

3 and 4 seem a little stuck so I was afraid to pull those harder. Worried that the boot will break/split and i will be stranded at the driveway unable to continue driving.

So i have yet to replace those coils. Car still runs the same after replacing coils 1 and 2.

 

What i noticed is that it seems to misfire more when the weather is hot and the black car has been baking in the sun all day (doesn't matter if the engine is hot too or not). Today after such day, the CEL started flashing after starting the car and idling. As previously, restarting the car fixed the flashing light but i could still feel the misfires.

 

Hooked up VCDS - this time it was cylinder 3 misfiring. So i'm hoping the problem is resolved when I either take it to a garage or gather some courage to pull the last 2 coils out with some force.

I also checked the misfire counts on cylinders - cylinder 3 was counting 1 misfire per 1000rpm.

Over the lifetime, it has counted around 13-18k misfires on some cylinders.

 

It seems that another issue has popped up too - intermittent and not at the same time as misfire fault codes.

P334B - Charge Pressure Control Actuator: Mechanical Malfunction

After some browsing it seems a common issue. Hoping it doesn't come to having to have the turbo replaced.

Wondering if this could be related to the misfires though as Ross-tech page says one of the possible symptoms may be: Reduced Idle quality and Engine Performance.