Reading Plugs

[rjjablo]

Changed the plugs for the first time. #2 Had the Plug Wire disconnected, #1,2,3 are all under what looks like a valve cover leaking, #6 is fouling and # 11 looks off.

Any Reason to suspect anything else for #1,2,3?

Likely Suspects for #6 and # 11

Spark Plugs III.jpg

[m6bigdog]

Hard to read plugs from a photo.
FWIW, Looks to me like Bank 1-6 is running rich (except #5) and 7-12 is overall running much better.
If you have assess to a DIS I would check fuel trims to see how balanced the banks are running.
The M70 engine, 1.7 DME fires the injectors in groups of 3. Cylinder/injectors 1-3-5, 2-4-6, 7-9-11, 8-10-12, are group fired therefore fuel trimmed in sets of 3 cylinders.
Hence, if one of the 3 cylinders is firing poorly the O2 will cause the fuel trim to affect fuel injection duration of the other cylinders in that set and bank.

Example, Plug #5 that running lean compared to plugs 1 & 3 in the 1-3-5 group is and indication.
Also, in the other group of that bank, Plug #4 looks leaner compared to plugs 2 & 6 in the 2-4-6 group is another indication.
The plugs in the other bank 7-12 look much more consistent and may very well do better if bank 1-6 performed better.

Having individual plugs with a lighter porcine may be either that cylinder's injector is slightly clogged or because an injector(s) in the group is making other cylinders run rich.
The Plugs that are darker-black could be either oil fouled, running rich due to a leaky injector and/or excessive low compression or could be due to an injector causing other cylinders to run lean.

IMHO:
Compression check or leak-down values are always good to know - just for the knowledge of the evenness of the cylinders and direct comparison to the plug color for each cylinder.
May want to pull all the injector and replace them or have them cleaned and tested to better evaluate their fuel flow properties.
May want to replace both O2 sensors if they have more than 50k miles and/or of if any of the cylinders burn oil. Oil burning plugs up the O2 sensor which causes the fuel trim to bias toward lean.
Also, the M70 has a fuel pressure regulators for each bank/fuel rail and if one of them is leaking it could cause a drop in fuel rail pressure, causing that bank to run leaner and longer crank time during start-ups.

[rjjablo]

Thanks, this is the kind of insight I needed

Did not mention
185K Miles
02 Sensors, no idea when or if they have ever been changed
Same with Injectors
Starts right up but runs very rough and rich and eventually smooths out, I am going to replace capacitors in the General Module Soon.

[PabloRock]

You could also have an intake manifold leak. That was the main cause of my rough idle and I think rich running. When I brought for emissions it said I was running rich. But not sure if that cured it totally, because when I brought it back to check, the car was too old to test. But running much better now. Not an expensive fix (you just need to seal them), but quite a bit of work. And use the correct plugs if you are changing them out. The Bosch are no longer the correct ones (they changed the specs). Use NGK BKR6EK.

[m6bigdog]

Thanks, this is the kind of insight I needed

Did not mention
185K Miles
02 Sensors, no idea when or if they have ever been changed
Same with Injectors
Starts right up but runs very rough and rich and eventually smooths out, I am going to replace capacitors in the General Module Soon.

At a minimum you will want to also test the Intake Manifold gaskets for leaking, as at start-up a rough idle that smooths out is typical of intake manifold leaks.
The noticeable rich idle is caused by cylinder misfires and the O2 enrichment that is caused with the unburnt oxygen reaching the O2 sensor.
So not only is the unburnt fuel from the misfiring cylinders exiting the exhaust the cylinders that are not misfiring are running rich.
While the general module capacitor replacement may provide positive results for body electrical functions it has nothing to do with engine systems performance.

Engine systems maintenance is critical in order to have any engine perform well after 27 years and 185k miles.
IMHO, the level of maintenance is significant and unavoidable for even BMW's premier V12 engine.

Given the experience you are having with the engine:
A detailed look at the engine fault codes with a DIS may help diagnose some issues.
Also, compression and leak-down testing is an informative test that helps establish the baseline for anticipated cylinder performance.
Engine oil consumption needs to be evaluated for excessive valve stem or oil ring sealing for each cylinder.
Included in the maintenance records there should be many items that will have been repaired so an M70 engine with that many miles can perform satisfactorily.

Beyond the O2 sensors & Injectors;
The Cam Oilier Hollow/Banjo Bolt fix needs to be installed and the valve springs, came lobes and followers will need to be closely inspected for damage/excessive wear irrespective of loose bolts every time the valve covers are removed.
Cam Timing in all likely hood will need to be adjusted to compensate for chain and sprocket wear. Replacing the cam chain, sprockets, chain tensioner and chain guides is also a possibility based on the conditions found during inspection.
Intake manifold gaskets and crankcase vent system will need to have been replaced if a leak is discovered or if the manifolds are removes and they become leak prone after 80k miles.
The above maintenance can all be completed when the valve cover gaskets are replaced.

The ignition systems maintenance could include plug wires, distributor cap and rotor. Typically the DME and ignition coil are function or fail components so replacement is not warranted unless the engine experiences a gross ignition system failure.
In an effort to maintain engine reliability, regular maintenance of engine cooling system is necessary to include inspection and regular replacement of the drive belts, fan & clutch, idler pulleys, water pump, thermostat, radiator, coolant reservoir and radiator & heater hoses within the last 60-80k miles if not several times during the 185k miles & 27 years to ensure these systems remain reliable.

[Dr. T]

So if one bank is found to be running rich, can it be adjusted with DIS?

[m6bigdog]

So if one bank is found to be running rich, can it be adjusted with DIS?

No,
FWIW, The DIS can display the fuel trim adjustments made by the DME to satisfy the O2 sensor feedback.
The O2 sensors are the calibration source for the DME to set the idle and part throttle Air Fuel Ratio of 14.7:1.
The DME MAP, RPM and MAF sensors manage part throttle power AFR but during engine full throttle the AFR is only controlled by the DME MAP and RPM.
The engines individual cylinder to cylinder balance will require compression, valve timing, injector flows, O2 sensor responses and fuel rail pressures to be within specification limits or engine idle smooth, part throttle and full throttle performance will suffer.

[rjjablo]

I have to get a computer that will read the codes
Intake manifold leaks strikes me as very likely considering the odd pattern of the Rich Cylinders
Valve Covers are going to come off as I definitely have a leak there
I am going to replace the o2 Sensors also

I will revisit all the rest when I get done with the low hanging easy fruit

Only maintenance history I have on this car is that the brake pads were replaced before I got it.