FSI constant misfire cylinder number 2

GTSpec

Member
Hi all,

I’m after some advice from the FSI experts. Back in August I bought a 96,000 mile FSI for recently retired father. The car was in great cosmetic condition but mechanically it had a few issues however the service history was extensive.

I noticed the car had a lumpy idle when I drove it back home which I put down to dirty injectors and possibly the wrong fuel being used recently.

I wanted to get the engine as reliable as possible for him so as a preventative measure I got the injectors professionally cleaned and serviced on an Asnu machine, cleaned the intake valves and lower intake manifold (flaps work perfectly), replaced the oil separator, all for coils for Bosch items and an engine service using NGK 4 electrode plugs. I also carried out a compression check and all cylinders showed 11 to 12 bar.

The engine has always had a lumpy idle which was down to random misfires on cylinder 2. This has got progressively worse and now it misfires constantly. I have checked for spark which is there and I have run a new earth strap.

Earlier I checked the in-take lift pump and it delivered 760ml of fuel in 15 seconds at 12.55v. I got 2.5 bar of pressure at the low pressure side of the fuel rail using a cheap eBay fuel pressure gauge. The injectors are all reading 1.6/1.7 ohms back to the ECU connectors. I rechecked the cylinder compression readings and they haven’t changed since August.

VCDS is giving codes 16686 and 16684.

One thing I would say is that it runs a lot rougher when the engine warms up.

Any suggestions based on experience? It is driving me mad now.

Cheers.
 

Robin_Cox

Member
What about lids - I'm thinking oil filler cap, fuel cap etc. If the seals on these are dried out and not sealing perfectly you could get some slightly random air ingress that could mess up mixtures, although I don't know how this would only affect cylinder 2.
 

GTSpec

Member
What about lids - I'm thinking oil filler cap, fuel cap etc. If the seals on these are dried out and not sealing perfectly you could get some slightly random air ingress that could mess up mixtures, although I don't know how this would only affect cylinder 2.
They seem fine. Cheers Robin.
 

PlasticMac

Member
I go for a wiring fault, so I'll peruse the circuit schematic for possibilities and come back, probably tomorrow.
Mac.
My Prime Suspect is the ECU connector, individual injectors and coil packs are controlled by the Motronic ECU, and all on J220. This is the only bit of the electrics which is cylinder specific.
Useful how to remove ECU from @A2Steve :
"Lift up the carpet on the passenger side
Turn the little black 'nipples' on the metal panel that's directly below the carpet
The metal panel removes
Inside you will see a black box with a load of wires going to it, that's the CCCU, the ECU is directly underneath.
You can remove the ECU without taking the CCCU out of the way but its far easier if you lift the CCCU out of the way.
There are two little tabs on the side of the CCCU that need pushing out of the way and then it just lifts up with the wires still attached
The ecu can then be pushed out of its holder
Once the ECU is out of its holder you can see that there are 2 block connectors attaching to it, these are released by pulling on the handle shaped part.

Refitting is just the reverse of the above.

It sounds long winded, but it will honestly not take longer than 5 minutes"

Mac. (acks to Steve).
PS: Look closely at Brown/Red and Red/Black wires and the connector pins they go to.
Brown/Red is # 2 injector. Red/Black is # 2 coil pack.
 
Last edited:

Weetank2

Member
Clearing codes then swapping coil packs around and rescan would eliminate them
Or identify a poor one

Any sign of discolouration on spark plugs

Any coolant loss /consumption
 

Andrew

A2OC Donor
My Prime Suspect is the ECU connector, individual injectors and coil packs are controlled by the Motronic ECU, and all on J220. This is the only bit of the electrics which is cylinder specific.
Useful how to remove ECU from @A2Steve :
"Lift up the carpet on the passenger side
Turn the little black 'nipples' on the metal panel that's directly below the carpet
The metal panel removes
Inside you will see a black box with a load of wires going to it, that's the CCCU, the ECU is directly underneath.
You can remove the ECU without taking the CCCU out of the way but its far easier if you lift the CCCU out of the way.
There are two little tabs on the side of the CCCU that need pushing out of the way and then it just lifts up with the wires still attached
The ecu can then be pushed out of its holder
Once the ECU is out of its holder you can see that there are 2 block connectors attaching to it, these are released by pulling on the handle shaped part.

Refitting is just the reverse of the above.

It sounds long winded, but it will honestly not take longer than 5 minutes"

Mac. (acks to Steve).
PS: Look closely at Brown/Red and Red/Black wires and the connector pins they go to.
Brown/Red is # 2 injector. Red/Black is # 2 coil pack.
Careful Mac, the FSI ECU removal has its quirks. Guru Tom's video...


Andy
 

s2ulk

Member
Hi all,

I’m after some advice from the FSI experts. Back in August I bought a 96,000 mile FSI for recently retired father. The car was in great cosmetic condition but mechanically it had a few issues however the service history was extensive.

I noticed the car had a lumpy idle when I drove it back home which I put down to dirty injectors and possibly the wrong fuel being used recently.

I wanted to get the engine as reliable as possible for him so as a preventative measure I got the injectors professionally cleaned and serviced on an Asnu machine, cleaned the intake valves and lower intake manifold (flaps work perfectly), replaced the oil separator, all for coils for Bosch items and an engine service using NGK 4 electrode plugs. I also carried out a compression check and all cylinders showed 11 to 12 bar.

The engine has always had a lumpy idle which was down to random misfires on cylinder 2. This has got progressively worse and now it misfires constantly. I have checked for spark which is there and I have run a new earth strap.

Earlier I checked the in-take lift pump and it delivered 760ml of fuel in 15 seconds at 12.55v. I got 2.5 bar of pressure at the low pressure side of the fuel rail using a cheap eBay fuel pressure gauge. The injectors are all reading 1.6/1.7 ohms back to the ECU connectors. I rechecked the cylinder compression readings and they haven’t changed since August.

VCDS is giving codes 16686 and 16684.

One thing I would say is that it runs a lot rougher when the engine warms up.

Any suggestions based on experience? It is driving me mad now.

Cheers.
This sounds identical to how our FSI (bought in October) drives albeit we just have an intake air leak fault code. I’ve changed the coil packs and the spark plugs and have had 3 tanks of shell v-power in thus far. That has improved the rough idle and hesitation but, like with your car, as it warms up it gets worse.

I had B&F autos, who are respected when it comes to A2s, look at the car earlier this month. They identified that the timing belt fitted 3,000 miles ago is not fitted correctly and that could be throwing the timing out. I suspect that is part of the problem but I also have a bad feeling that it won’t be the complete solution (and a new timing belt is not cheap of course). I have ordered a proboost ECU with A2steve’s help which I will get at some point in the new year and so will be interesting to see whether that solves the problem. If in the meantime you solve the issue through Mac’s suggestion then let us know!
 

GTSpec

Member
My Prime Suspect is the ECU connector, individual injectors and coil packs are controlled by the Motronic ECU, and all on J220. This is the only bit of the electrics which is cylinder specific.
Useful how to remove ECU from @A2Steve :
"Lift up the carpet on the passenger side
Turn the little black 'nipples' on the metal panel that's directly below the carpet
The metal panel removes
Inside you will see a black box with a load of wires going to it, that's the CCCU, the ECU is directly underneath.
You can remove the ECU without taking the CCCU out of the way but its far easier if you lift the CCCU out of the way.
There are two little tabs on the side of the CCCU that need pushing out of the way and then it just lifts up with the wires still attached
The ecu can then be pushed out of its holder
Once the ECU is out of its holder you can see that there are 2 block connectors attaching to it, these are released by pulling on the handle shaped part.

Refitting is just the reverse of the above.

It sounds long winded, but it will honestly not take longer than 5 minutes"

Mac. (acks to Steve).
PS: Look closely at Brown/Red and Red/Black wires and the connector pins they go to.
Brown/Red is # 2 injector. Red/Black is # 2 coil pack.
Cheers for that Mac.

I checked the injector wiring back to the ECU connector earlier. Will check the coil after Christmas as the car has now gone back to my dad. Wonder if the injector and coil drivers within the ECU can go bad?

Will also check the timing as per S2ulk’s recommendation.

The misfire seemed intermittent when driving it back tonight.

Thanks again.
 

999fire

New Member
My Prime Suspect is the ECU connector, individual injectors and coil packs are controlled by the Motronic ECU, and all on J220. This is the only bit of the electrics which is cylinder specific.
Useful how to remove ECU from @A2Steve :
"Lift up the carpet on the passenger side
Turn the little black 'nipples' on the metal panel that's directly below the carpet
The metal panel removes
Inside you will see a black box with a load of wires going to it, that's the CCCU, the ECU is directly underneath.
You can remove the ECU without taking the CCCU out of the way but its far easier if you lift the CCCU out of the way.
There are two little tabs on the side of the CCCU that need pushing out of the way and then it just lifts up with the wires still attached
The ecu can then be pushed out of its holder
Once the ECU is out of its holder you can see that there are 2 block connectors attaching to it, these are released by pulling on the handle shaped part.

Refitting is just the reverse of the above.

It sounds long winded, but it will honestly not take longer than 5 minutes"

Mac. (acks to Steve).
PS: Look closely at Brown/Red and Red/Black wires and the connector pins they go to.
Brown/Red is # 2 injector. Red/Black is # 2 coil pack.
Hi guys, just following up on this thread. My car whilst returning to work one day from lunch just unexpectedly just quit, engine cut out and nothing I could do to start the car. Traced the fault to corroded wires on my ECU :( I still don't know as it it is well protected from the elements, just a thought to try this as well when going to the bother of removing the ECU :)
 

PlasticMac

Member
Cheers for that Mac.

I checked the injector wiring back to the ECU connector earlier. Will check the coil after Christmas as the car has now gone back to my dad. Wonder if the injector and coil drivers within the ECU can go bad?

Will also check the timing as per S2ulk’s recommendation.

The misfire seemed intermittent when driving it back tonight.

Thanks again.

Failure of coil pack, and injector drivers is very possible, and, practically impossible to check, other than by ecu substitution. The immobiliser makes substitution difficult.
Mac
 

Edwrai

Member
This sounds identical to how our FSI (bought in October) drives albeit we just have an intake air leak fault code. I’ve changed the coil packs and the spark plugs and have had 3 tanks of shell v-power in thus far. That has improved the rough idle and hesitation but, like with your car, as it warms up it gets worse.

I had B&F autos, who are respected when it comes to A2s, look at the car earlier this month. They identified that the timing belt fitted 3,000 miles ago is not fitted correctly and that could be throwing the timing out. I suspect that is part of the problem but I also have a bad feeling that it won’t be the complete solution (and a new timing belt is not cheap of course). I have ordered a proboost ECU with A2steve’s help which I will get at some point in the new year and so will be interesting to see whether that solves the problem. If in the meantime you solve the issue through Mac’s suggestion then let us know!

I’d do a leak down test


Sent from my iPhone using Tapatalk
 

Edwrai

Member
Even though the cranking compression reading is the same as the other 3 cylinders?

Cheers

Yes.

Everything that has been tried it sounds like a mechanical misfire and a leak down will discount or confirm.

Will also show where the fault is, valves, rings head gasket etc.


Sent from my iPhone using Tapatalk
 

Gsting

Member
hi to all fans.
I have been following your forums for some time because a few years ago I bought a 90 CV TDI after having owned a 3L that I stupidly alienated more than 10 years ago.
I also recently bought an FSI 1.6 in Germany with 120,000 km.
This one has practically new interiors, but has some mechanical work to do. when I tried it it had no engine defects and no fault codes. Brought to Italy and used in the city, with very hot engine it struggles to start and then has misfire on cylinder 3. I changed all the spark plugs and coil 3, which had detached rubber and everything is ok until the engine has to be restarted heat: the engine runs badly and then the cylinder misfire appears 3.
I am cleaning the injectors with a Bardahl additive. I think the problem could derive from the injector that does not seal in the cylinder.
I'll let you know how it will evolve.

Also I read in the thread that you replaced the oil separator: I have a hard time finding it on the internet. can it be found easily in England?

Greetings from Italy
 
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