Possible MAF failure.

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Interestingly, the plugs on the drivers side bank are full of carbon, the passenger side plugs look pretty normal

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To me that says dud O2 sensor.
Did you use sealant on the threads? This is a nono.
Perhaps swap the o2 sensors and see if the main rich problem moves to the other side. The fact that the banks are different would seem to preclude the MAF. Exhaust manifold leaks can be a factor?

My experience says that in closed loop the MAF has little input . The O2 sensors control mixture almost totally. In fact on a 14CUX the MAF is adjusted rich for o2 sensors as it is apparently easier to take fuelling out than add it. If you are nailing it and going into open loop then the MAF will play a bigger part.

While a 14CUX is not as sophisticated as the GEMS and Motronic the principles are the same.
Regards PhilipA

Thank you for your thoughts PhillipA, yes that does make sense, I'll try swapping them and see what happens.
Although the fault codes are currently showing both sides have an issue.
I only used anti seize on the thread, no sealant, was very careful to keep the sensor clean.
I'm not hearing any obvious exhaust manifold leaks, it's all pretty quiet.
The 02 sensors are aftermarket, I'm wondering if i should have put genuine sensors in?

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The 02 sensors are aftermarket, I'm wondering if i should have put genuine sensors in?

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Bosch Motronic can be fussy over sensor brands.
I would recommend Bosch sensors .
You do not really have to pay a ransom for the sensors with the correct connectors. You can buy a general Bosch sensor and swap over the plugs by cutting them off the old one and attaching to the new.

I have found that you have to crimp connect the wires rather than solder .
Regards PhilipA

I cleared the fault codes, went for a drive and the codes that pop up are for both sensor heaters and a mixture adaption error.

*P0135=Oxygen sensor heater upstream catalyst Bank1 Drive cycle C persistentely present
*P0155=Lambda sensor heater upstream catalyst Bank 2 Drive cycle C persistentely present
*P0175=Mixture adaption factor FRA Bank 2 drive cycle C (signal too high) persistentely present, (which would result in the overfuelling and carboned plugs on that side).

Then I swapped the sensors over, cleared the fault codes, reset the adaptive values and went for a drive.
After resetting the adaptive values it idled so smootly you could barely tell it was running, by the time I got back, it was idling a bit roughly again.
Checked the fault codes again, it came back with the same codes as above, with an additional code

*P0175=Additive adaptive mixture correction TRA bank 2 Drive cycle B, (signal too high), currently present.

So it appears both 02 sensor heaters are not operating correctly.
I read on another forum sometimes aftermarket sensors do not heat up fast enough and the ECU logs a heater fault.
I checked fuse 26 and that is ok (02 sensor heater circuit)

Interestingly the overfuelling errors stayed on the same side after swapping the sensors over.
I removed both sensors again to find the same side had carbon showing, even though it was another sensor in there.

So there is something about bank 2 that is causing a rich condition.(ie the bank is running lean but being compensated by the O2 sensor) It cannot be MAF related or would affect both banks.

I still wonder about either an exhaust leak or an inlet leak on that bank. The oil vent system comes out of the drivers side rocker as does AFAIR the vacuum hose for the brakes and the evap system. Inspect all of the pipes and suck on the brake booster hose. The crankcase vent system can get blocked and the spring thingy has to be cleaned or replaced , but IMHO the vacuum pipes are the answer.
Check the operation of the evap system valve.
Regards PhilipA

Brilliant advice as always Phillip, thankyou, I will investigate your suggestions and let you know how I go.
I ordered 2 genuine bosch sensors today, they will go on when I get them.
Thanks again!

Just a tip for hunting vacuum leaks:

I made hunting for vacuum leaks a bit easier by using an old smoke generator and a pressure hose. It would basically push smoke into the air intake of the car (after the maf :P) and smoke would come out where there are leaks.

Chears,
-P

On further reflection the vacuum lines come from the "bar' across the front of the Thor manifold and would affect both banks but the thought is still valid.
Regards PhilipA

That's very inventive prelude, good thinking!
I did try the old carby cleaner spray trick around the vacuum hoses, but didn't find anything.
I might give that another go and see what I can find.

I have it solved!
After waiting what felt like an eternity for the Bosch sensors to turn up, they arrived today, so I got straight to it.
Replaced both sensors, cleared the fault codes and did an adaptive values reset, which resluted in it sounding much better straight away.
I've been for a bit of a drive and checked for fault codes with none present.
It's idling so much better now without the vibration that was occuring.
I replaced the carboned plugs on bank B and noticed the existing ones were still showing carbon, but they were all clean on the tip where the spark would be, which is a pretty positive sign to me.
I'll replace the plugs on the other bank so they are all new.
So the moral of the story, only use genuine Bosch 02 sensors!
It wasn't happy at all with aftermarket sensors.

While I was waiting for the sensors to arrive, I also checked around for any vacuum leaks, one thing I did find was the vacuum hose that runs from the plennum to the rocker cover (where the oil seperator is) was a bit loose at the plennum end. I was able to move the black plastic connector slightly with my hand, so i tried to pull the hose off and it broke in half straight away.
So be aware those connectors become very brittle and fragile with age and break very easily.
The hose itself seemed ok, so I replaced the connector and also replaced the oil seperator which was a bit gunked up with oil.

I probably should take it for a bit of a drive now to try and blow out the carbon deposits.
Thank you for your help eveyone, Cheers, Pete.