Phantom rough idling issue in a straight V8 Discovery 2

[MAF Diver]

Dear brain trust:


My D2a V8 has a rough idling issue which I can't seem to fix. It also throws up a lot of O2 diagnostic trouble codes. Car has around 120,000 km on it.


Confirmed:


P0130 - O2 bank 1 circuit malfunction
P0171 - system too lean bank 1 (passenger's side)
P1171 -
P1174 -
P0150 - O2 bank 2 circuit malfunction (driver's side)
P0174 - system too lean bank 2



Here's what I've tried in order:


I changed spark plugs (8x NGK)
I tried 3x different MAFs (2x brand new Bosch, 1x from a wreck)
I changed air filter, and air filter top lid (clamp was broken)
Mechanic changed spark plug leads (aftermarket, grey ones)
I changed O2 sensors (2x new Bosch)



Unrelated work done:


Mechanic: changed rocker cover gaskets (big leak before), thermostat, water pump, coolant flush, throttle body base (big coolant leak).
Mechanic visually inspected at vacuum hoses, doesn't see any damage or cracks.



Numbers I'm getting via OBD2:


0km/h (idle, coolant 26-40C)
980-872 RPM
40-20 kg/h MAF
Bank 1: 0.45-0.54V, 7-19% trim
Bank 2: 0.37-0.75V, 2-11% trim


0km/h (idle, coolant 81-87C)
614-703 RPM
10-16 kg/h MAF
Bank 1: 0.03-0.06V, 25% trim
Bank 2: 0.01-0.06V, 0-25% trim


11km/h (87C)
1639 RPM
108 kg/h MAF
Bank 1: 0.89V 17% trim
Bank 2: 0.74V -6% trim


53km/h (87C)
1286 RPM
29 kg/h MAF
Bank 1: 0.04V 15% trim
Bank 2: 0.04V 17% trim


48km/h (87C)
1684 RPM
91 kg/h MAF
Bank 1: 0.39V 2% trim
Bank 2: 0.53V -3% trim


(Trim and MAF numbers have been rounded.)






What do you suggest that I try next?

[biggin]

Did you do the reset thingy with the Nanocom after replacing the sensors?

[MAF Diver]

Did you do the reset thingy with the Nanocom after replacing the sensors?

You mean clearing the error codes? Yep, I cleared them with my ODB2 reader (Vgate device, iOS app Car Scanner).

I don't have a Nanocom (pricey!)

[shack]

You need to reset the adaptions.

[Tins]

I don't have a Nanocom (pricey!)

Not compared to the parts canon.

[biggin]

You need to reset the adaptions.

Yeh, that’s what I meant. [emoji106]

[MAF Diver]

You need to reset the adaptions.

Ah, gotcha. Does disconnecting the battery do this?

Can other tools do this apart from a Nanocom? A friend has a fancy Autel but he's out of town at the moment

[shack]

Ah, gotcha. Does disconnecting the battery do this?

Can other tools do this apart from a Nanocom? A friend has a fancy Autel but he's out of town at the momentI don't know if disconnecting the battery will reset or not, other tools would work bit I don't know which ones.

The Motronic has pretty good OBD2 compliance so should be reasonably easy to sort.


Secondly, whilst I'm unable to get to a computer at the minute, I quickly did the sums in my head on your MAF readings.

You quote an RPM of 900 with a mass air reading of 40 kg/hr, that alone should set off alarm bells. A 4 litre 4 stroke engine @ 900 RPM should =

8*500mg*(RPM/2)*60

= 4000*450*60= 108 kg/hr @ 900 rpm.

The 500mg is a rough guess based on sea level and pleasant ambient temps!!

If the engine is fuelling based on 40 kg/hr, it will be running dangerously lean.

What I don't understand is that it *should*
Still be running closed loop, although maybe it's so far out of whack the adaptions are OOR, so open loop it is...??

Either way, don't run it like that, it'll be a bit hard on the valves.

*Disclaimer, I know almost nothing about the Motronic 5.2.1 engine management system and petrol engines!!

[shack]

Update to the above..

I had opportunity to test car scanner on a V8 D2 and got the same air mass reading.

I'm pretty certain that the car scanner app is misreporting g/s as kg/hr.

So 40 g/s = 144 kg/hr.

That means the issue lay elsewhere.

And that's why dedicated tools are the go.... It stops premature firing of the afore mentioned Cannon.

[MAF Diver]

Oh, interesting! Thanks for looking into this mate!

The mechanic looked at it with his Solus Edge Snap-On (way more advanced than the Car Scanner app) and it showed the same kg/h readings. Does your Nanocom show something else?

Also, I noticed that while driving, both ECUs run in closed loop, but when stopped at a traffic light, I get ECU2 at open loop (but ECU1 stays closed loop):

190399

(Also, there's two ECUs?)

[shack]

Nanocom shows g/s, as I said... You are always better off with dedicated tools.

As to what your problem is, it could be anything, if course a dedicated tool MAY show a fault code that the one size fits all solutions you have been using don't.

Possible failures are O2 sensors, cam position sensor, coil packs, spark plugs, spark plug leads etc etc.

(I haven't re read the post to see what you have changed.)

I don't think aftermarket tools will show the cam sensor properly from memory.

There is also knock sensors and of course the fuel gauge in the tank that can cause running issues, although probably only when you have a very low tank with a gauge not showing that.

There isn't 2 ECU's, I'm aware that car scanner reports that.

The NAS vehicles also had O2 sensors after each cat, ROW spec don't, they only have upstream sensors... It's possibly confusing itself there somehow but I don't see why??

[MAF Diver]

So I finally made a DIY smoke machine and have smoke coming out from somewhere deep in the engine.

But I can't see where exactly? Here's a video:




https://www.youtube.com/watch?v=nMaEBdeAjf4


Would you say it's a big vacuum leak?





Questions:

1. What part(s) are easy to remove to get a better look?

2. Should I connect the smoke machine to somewhere else as well to check? Currently fed in from where the MAF would be.

3. Is it safe to drive the car while I figure out the source/fix? Or can I damage injectors, O2s, cats, etc.?



tl;dr
- Coming from deep somewhere near the injector area? Gasket? There's also a few smaller hints here and there in my videos.
- None coming from the oil cap when removed.
- A bit coming from brake booster hose. But not much?

Birds eye view from top down:

Here you can see it also comes out a bit up top nearer to the windshield.

https://www.youtube.com/watch?v=EVlTqlMX9ho
Air leak from booster cable:


https://www.youtube.com/watch?v=96iE5A0mu0I

https://www.youtube.com/watch?v=yACEGhBVPZw
Taking off the oil cap:


https://www.youtube.com/watch?v=iltunw5A8kg

[shack]

Running a petrol engine too lean can definitely damage it. Cats and valves are at risk.

[PhilipA]

Seeing it is in the V my guess is that the inlet manifold (valley) gaskets to heads are leaking. They can get loose over time. Or the end seals of the valley gasket have failed.
Regards PhilipA