Engine misfiring + fault codes - any thoughts?

[miniyazz]

Hi guys,
New to this forum but bought a MkIV 2.8L V6 4MOTION last week so may be around a bit

Anyway long story short, heavy downpour today, drove a decent journey (~20miles) and noticed a small drop in power, rough idle and a bit of vibration (seemed to settle from about 4k RPM upwards).
So got back, plugged in my cheap OBD2 thing and it reports three fault codes: P0160, P1199, and P0302.

P0160 - O2 Sensor Circuit No Activity Detected
P1199 - O2 Sensor Heater Circ., Bank2-Sensor2 Electrical Malfunction
P0302 - Cylinder 2 Misfire Detected

So obviously I'm wondering what the likely cause is and what to do about it. By the way, I checked for fault codes when I bought it and it came up clear.. although it could have been cleared before I saw the car, of course.

A bit of research tells me that a faulty coil could be the problem, given the weather and my engine (24V). Does this seem liable to cause these fault codes? I presume if this seems likely I can get it/them replaced by VW free of charge due to the recall (although I don't know if it's already had them done).

Alternatively, am I looking at separate problems e.g. with a faulty O2 sensor and something else causing the misfire?

Cheers for any advice

[miniyazz]

A quick update: I changed two of the coil packs around today (thanks to abydielsgli's thread). The one over cylinder 2 was absolutely covered in what looked like grit and muck. I brushed it off as best I could (though largely pointless I expect given the connection is inside?) and swapped it with #3, and lo and behold, the misfire code is now for cylinder 3. I think we have a culprit.

Any thoughts on if the O2 sensor code is a spurious reading because of the misfire? I checked the sensor today and the post cat (sensor 2 bank 2) reading did adjust between ~0.4-0.5V, so I don't think it's broken. And the fault code hasn't resurfaced since I cleared the ECU codes..

[jaso028]

before worrying about your o2 I would give it a few days.. When one of my coils went the other day, Car obviously ran like crap. Had the flashing CEL and then once the new coil was in my CEL was on solid! finally when I got home I through VAG on it and had 8 codes! 2 for cyl 6 misfire, then crank, cam and, o2 sensor codes...

a bad coil will make a ton of other sensors think there is way more wrong... so give it a few days and see what happens... now since Tuesday I have been completely fine and have driven over 400miles...

[miniyazz]

before worrying about your o2 I would give it a few days.. When one of my coils went the other day, Car obviously ran like crap. Had the flashing CEL and then once the new coil was in my CEL was on solid! finally when I got home I through VAG on it and had 8 codes! 2 for cyl 6 misfire, then crank, cam and, o2 sensor codes...

a bad coil will make a ton of other sensors think there is way more wrong... so give it a few days and see what happens... now since Tuesday I have been completely fine and have driven over 400miles...

Thanks for the tip. I've now replaced the faulty coil unit (£35 ) and all is well. I've got a decent length trip coming up so will see how it does on that.. no problems anticipated!

By the way, there's a few used ignition coils on the 'bay for ~£15 delivered. They're used and are quite old (the ones from ~7 years ago with the letter D at the end), but I was wondering if it might be worth having a cheapo but functioning coil just to lug around with me just in case. Only half the price of a new shiny one though.. decisions, decisions.

[miniyazz]

Alright, I've driven around for a bit (about 400 miles) and the O2 sensor codes have returned, so there may actually be something wrong with it. The post-cat O2 sensor doesn't really do that much though does it - how important is it if it's giving fault codes?

[2003gtivr62.8liter]

U might wanna check the cat. Just my .02

[miniyazz]

Bugger, hope it's not that, they're not cheap
I've got vag com on order so will give it a test once I've got it up and running.