Call out to V12 owners or forum experts....serious random issue

[westaussie323i]

I am hoping someone has a couple of clues to the issue I am having. I had a random issue that caused the car to feel like it was running on 6 cylinders and feels like it is starving for fuel but yesterday I was in the city and it wouldn't do more than 20kmh and I limped over to the shop I use when I am in town. The ran diagnostics and it had multiple misfires and their system noted that a throttle body was out of range on a previous service. There was no record of a fuel filter being done so I had them do that while it was there. I took it for a 10 minute drive and apart from a bit of hesitation from standstill it ran fine and no apparent misfiring. Got back to the shop plugged it in and it showed multiple misfires but was running smoothly so I went on my way then 15 mins away from shop started doing it again. I thought $%^&* it and hit the freeway and it would sit on 100/110kmh but you could feel it misfiring a little but very low on power from standstill.
I stopped for a coffee bot back in the car and the fault was gone again then came back 30 mins later. It had new distributor caps and rotors, rear speed sensors a few months back but other than that I am unsure as to what else been done.
Car has been a garage queen with only 150,000km in 22 years. One thing that stood out was after it reset itself it felt like it had more power (compared to when it was running ok)

Any idea's greatly appreciated as I am a log way from my normal shop

[RIboater2]

There are so many possibilities but were there any codes other than misfires? A long shot, but because we do still have cap rotor and wires, you could have an arc. Have you moved or touched any of the wires recently? One time, I had done the water pump and the hose clamp was so close to the rotor cap it was arcing right through the cap. That was throwing the entire bank misfire. Another time a wire ran too close to another piece of metal and had a misfire on a single plug. In complete darkness you can actually see, and in some cases hear, a spark arcing.

[tomquic]

G'day mate ... sounds like a MAF issue to me .. I'd have a look at Timms site .. plenty of info there .. and lots of guys who have yr model .. http://www.meeknet.co.uk/E38/Index.htm on the 7 series register uk . lots of good guys who want to help .. and its all RHD with same electrics as Uk rather than US which does have some differences .. Good Luck ...

[Timm]

A couple of things spring to mind - if the cylinder misfires were all on one bank (1-6 or 7-12) then you could well have either a blocked catalytic converter on that bank - or - and probably more likely, you have a failing coil on that bank, these are known to give up when hot.....

[tomquic]

A couple of things spring to mind - if the cylinder misfires were all on one bank (1-6 or 7-12) then you could well have either a blocked catalytic converter on that bank - or - and probably more likely, you have a failing coil on that bank, these are known to give up when hot.....

Ha .. Hiya Timm ... lurking here too are you ... good onya mate . Hope all well in yr world . Cheers Tom

[exeed]

I presume you have missfires in one bank either 1-6 or 7-12, in that case I would check if your main key is programmed to both DMEs. It might be, that one engine computer simply does not work with one of them. I had the same problem when took the car to BMW dealer and took it back, they have reset all the settings and engine ECU was not programmed to a key. If that make sense. Then your engine will only run using half of the cylinders.

[westaussie323i]

Hi Guys
Thanks for the suggestions and it had me baffled, running perfectly most of the time and perhaps I made the mistake of assuming the shop had done everything right when the car was in the shop with previous owner. I should have taken photo's of the autologic screen but that's life. RIboater2 got me thinking about the spark plug leads as I knew the caps/rotors had been replaced. I removed the MAF's and cleaned them plus contact cleaned theie plugs, put it back to together but still a bit hesitant.
So I wiggled some leads but none had come out but not having owned a V12 before I soon realised that the leads have a positive clicking sound when seated properly and 3 on one bank and 2 on the other hadn't been seated properly and one wasn't even seated at all. Took it for a 20 minute run hitting redline a few times and she didn't miss a beat. Fingers crossed this solved the problem.
The lesson being I should not trust work is done correctly every time and I need to become a wiz using diagnostics software in future.

[740ilDuke]

My 1998 (70k miles) had the same issue, ended up being a bad DME. But mine was only running on one bank, never both.

Sounds like you may have solved it.

[tomquic]

Hi Guys
Thanks for the suggestions and it had me baffled, running perfectly most of the time and perhaps I made the mistake of assuming the shop had done everything right when the car was in the shop with previous owner. I should have taken photo's of the autologic screen but that's life. RIboater2 got me thinking about the spark plug leads as I knew the caps/rotors had been replaced. I removed the MAF's and cleaned them plus contact cleaned theie plugs, put it back to together but still a bit hesitant.
So I wiggled some leads but none had come out but not having owned a V12 before I soon realised that the leads have a positive clicking sound when seated properly and 3 on one bank and 2 on the other hadn't been seated properly and one wasn't even seated at all. Took it for a 20 minute run hitting redline a few times and she didn't miss a beat. Fingers crossed this solved the problem.
The lesson being I should not trust work is done correctly every time and I need to become a wiz using diagnostics software in future.

Pleased you found the issues mate ... the simple ones are the nicest ...

Get INPA .... easy and tells you so much .. some good guys in UK sell it over the 'bay' or Timm knows ..

[absolutezero273]

Glad to hear you got that one figured out. And quickly, too!

[exeed]

"I soon realised that the leads have a positive clicking sound when seated properly"

What do you mean by that?

[westaussie323i]

well apparently I didn't....went for another drive
all sweet...stopped to buy some fuel conditioner stopped for 5 minutes....doing it again so drove it home and parked it up. Haven't had much luck getting the inpa program running but remembered I had a bluetooth unit I was running with Torque Pro so I got these faults to show up and I cleared them but haven't been for another drive yet and out of curiosity unplugged the left hand MAF which didn't change a thing or log a fault. Runs like a watch currently.
Do these faults indicate limp mode or will that show up as a fault code on its own?
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[Timm]

I'm not sure if Torque Pro can access the Bank 2 DME - but, there is a MAF error on Bank 1 (which is the left hand bank as you face the engine - and the RIGHT HAND MAF as you face the engine). I would try swapping the MAF's from side to side to see if the errors follow the MAF.

But, we cannot be sure that you have misfires on all cylinders (which would be a fuel supply issue). If the misfires are confined to one bank then, as I said earlier, coil or blocked cat on that bank.....

[westaussie323i]

When the leads are pushed all the way in they make a sound a bit like a ratchet. I will try and get the INPA software running (not my strong point)
Drove the car again tonight and with no issues.
Can you remove the cats on these engines as we have no smog testing here or do you open a tin of worms with the DME?

[westaussie323i]

I saw a couple of videos that showed disconnecting the MAF will cause the engine to stop if operating correctly. I tried that on mine with both and either/or but slight hesitation and kept running....is this test applicable to these engines?

[XAlt]

I saw a couple of videos that showed disconnecting the MAF will cause the engine to stop if operating correctly. I tried that on mine with both and either/or but slight hesitation and kept running....is this test applicable to these engines?

On the M70 removing one MAF will cut fuel supply to the appropriate bank, disconnecting two MAFs will obviously cause a stall out. It's very useful for for diagnosing which bank runs like crap.

Pre-1999 V12s don't really care about the cats, feel free to cut them out.

[westaussie323i]

Still getting the misfire codes and as Timm suggested I don't think Torque can read 2 dme's so only reporting bank 1 misfire on all cylinders. Disconnected both MAF sensors at idle with a brief hesitation she kept running pretty smoothly