Engine ran a bit rough yesterday

Adrian E · #1 27th December 2018, 06:02 AM

Dave will love you for that one! Looking at pics of the cats off my old car here:

http://forum.a8parts.co.uk/showthread.php?t=12234

You can see the passenger side one is, mercifully, part of the shorter cat so doesn't involve removal at the downpipe.

Cat will potentially need to come off and much soaking of the thread to get it out. I don't recall it being an arse-buckling price either. Might just be possible to remove in situ

A

johnny_quattro · #2 27th December 2018, 11:42 AM

Thanks for your update, Adrian.

I'm sure Dave will take it in his stride... although having said that, I've noticed recently that my current A8L has started to display that unmistakable weird oil smell when a seal goes and it starts to drip on the catalytic converter. This was something my previous A8 suffered from. It's made me wonder whether the sensor is getting temporarily coated with oil from the aforementioned leak as I've had no rough running since?

Let's see what DS Autowerks discover.

MikkiJayne · #3 27th December 2018, 02:58 PM

Usually the burning oil smell is from a gearbox seal so much lower down than the front O2 sensors. The engine doesn't tend to leak where it could get on to the sensors, but it wouldn't hurt them anyway since the active bits are inside the exhaust pipe.

johnny_quattro · #4 28th December 2018, 10:26 AM

Quote:

Originally Posted by MikkiJayne

Usually the burning oil smell is from a gearbox seal so much lower down than the front O2 sensors. The engine doesn't tend to leak where it could get on to the sensors, but it wouldn't hurt them anyway since the active bits are inside the exhaust pipe.

Thanks MJ; I now consider myself educated.

johnny_quattro · #5 22nd January 2019, 11:40 PM

This one has come back to bite me on the bum....

Car started perfectly today and drove for around 6 miles and then I suffered a huge loss of power. I thought my gearbox was playing up and then I heard the engine running like a bag of spannners, like 3 or 4 cylinders instead of 8 so it was as lumpy as duck... intentional misspelling there. I eventually shafted the battery due to the countless attempts to get the engine to 'catch; as the engine simply wouldn't run normally and tickover was something around 200-300rpm. No power to move forward at all.

Was able to switch the engine off and read codes which came back with the aforementioned issue with the O2 sensor/bank message so I'll have to arrange for a low-loader no doubt in order to get Helga back to a nice warm garage. RAC didn't pick up the phone, and when I tried to join the AA (as a back-up option), they told me it was going to take them until 01:30 to reach me so I kindly refused their offer. Dad came over in the diesel Clio and it managed to tow my limo/tank about 300 yards up the road to a safer place. My only advice from tonight's escapade is that I know now exactly how much work my PAS pump works, as well as the servo-assistance on the brakes and it took almost a herculean effort from my skinny frame to either brake or turn the steering wheel.

I'll get the car back to the local garage. DS Autowerks is not an option at the moment but I will have to sort that out first thing in the morning,

MikkiJayne · #6 23rd January 2019, 08:27 AM

Do you have VCDS? Bad running with failed O2 sensors implies a bad MAF, since the O2 sensors normally compensate for it.

If you go to measuring block 99 in VCDS and then switch to Basic Settings it turns the O2 sensors off and runs just on the MAF. If it runs worse, the MAF is likely at fault. If it runs better, the O2 sensors are at fault.

If you don't have VCDS then just unplug both O2 sensors and see how it behaves. If it won't start, put them back and clear the codes then unplug the MAF and see how it behaves then. Obvs ignition off when dis/connecting anything.

johnny_quattro · #7 24th January 2019, 01:10 PM

MJ - thanks for your reply/advice.

Unfortunately I don't have VCDS or the 'Lite' version either.
My dongle is OBD Eleven / smartphone app

Car was transported back to my local garage on a low-loader and they are currently looking at it. I've sent them details of your suggested troubleshooting skills so will have to wait and see. DS Autowerks is an option if the local garage has no joy. I really appreciate your invaluable knowledge, so thanks.