Engine Misfire - Passat 2008 3.2 V6

[ronnie136]

Hi,

The engine on my 08 Passat 3.2 V6 Estate is misfiring and I'm hoping someone on here might have some ideas as to what it might be.

The misfire started recently (ironically I first noticed it whilst driving it to be serviced).

It was initially showing as a misfire on cylinder 5, so I had the coil pack on that cylinder replaced and all was good for a day or two, then the misfire reoccurred.
Taking it back to the garage I had the spark plugs and other 5 coil packs replaced. After picking up the car it's worked fine for a week then suddenly yesterday the misfire came back worse than before.

It was low on petrol so I've been out filled it up with BP Ultimate 97 and given it a blast down the local dual carriage way to rule out a dodgy bit of fuel left in the tank.

I do have an OBD dongle so I plugged it in and it's showing the following error codes:

P0300 Random/Multiple Cylinder Misfire Detected
P0305 Cylinder 5 Misfire detected
P0305 Cylinder 4 Misfire detected
P0305 Cylinder 6 Misfire detected

I can give the garage another call in the morning but I'm hoping one of the guru's on here might have some ideas?

Any help/suggestions would be greatly appreciated.

Thanks in advance.

[turboextreme]

it could be caused by carbon buildup. The 3.2 VR6 engine used in the B6 Passat is direct-injection and is know to suffer carbon buildup on the intake valves just like all DI engines (except the rare newer ones with secondary injectors that squirt the tops of the intake valves to prevent this issue). Buildup happens faster on some DI engines than on others, and in the VR6 FSI buildup happens much more slowly than in the direct injection engine variants even though it still happens. If you do a lot of short trips in town and never get the engine hot for a long period of time deposits will probably build up faster.

[RichardSEL]

Probably the injector wiring loom. If what they did on the 2.0L (BPY and BWA) is anything to go by, with only one earth return, it's that.
Coz of the heat it gets brittle after a time, and when disturbed never gives a good earth return again, so has to be changed for new.

I had this when I had my coils' recall done. Eventually main agent changed out loom FOC
There's been others with TDI that have had their injector recall and same happened needing change of loom

Connectors or wires themselves I dunno

[Crasher]

At high mileage and when having been run on long life oil change intervals, these units can develop problems with the cam chains and the VVT units which can cause misfire problems and an OBD code reader may not pick up the fault codes this problem would generate such as cam and crank sensor correlation.

[Dunconi]

All of these cylinders on are the same bank (bank 2). This suggests that anything common to bank 1 and bank 2 can be ruled out, such as the MAF, fuel pump, cam and chains, etc. Interestingly, the VR6 engine shares cam shafts between both sides of the "V". It could be blocked injectors, but the probability of only blocking those on one bank are small.

Can your diagnostic tool check your fuel mixture, can you smell unburnt fuel in the exhaust, are your tail pipes "sooting up" more quickly than normal, idle speed low (500 rpm)? If so, one of your Lambda sensors may have failed.



Your garage will most probably have reset the fault codes and reset the engine to default after the ignition coils were replaced. The fact that the fault returned after after a few days suggests that the ECU has adjusted its settings back to the condition causing the misfiring. This can be due to a faulty sensor or part confusing the ECU into making a incorrect compensation/adjustment.

This is the best I can do to help without more information.

[ronnie136]

Looks like it's being caused by a split PCV valve? It's an issue with pressure in the engine, runs fine if you remove dipstick or oil cap.

Garage is trying to source a replacement but seems it only comes as part of the rocker cover so part is ~£180+VAT

[Crasher]

It has been re-designed twice since your car was built, part number 03H 103 429 H and £214.33 inc. VAT.