Ignition coil ground strap M62

[Panamera1988]

My question is can a bad ground strap that is attached to coil cause a misfire on that bank? Is the wire going on top of the ignition coil or beneath? Does both banks have one ground strap? And on which cilinders are straps?

[R Shaffner]

Here you go:

Ground Strap.jpg

Note how the ground strap connects the head to the same stud that the brown wire connects to. (In the middle of the head, not where the arrows point.) Important ground connection for the heads. Straps are on both banks.

[Panamera1988]

I will try to campare this with mine, I am chasing idle misfire on one bank and its related with something electric, ground strap is next…

[Panamera1988]

So this is mine ground strap on coil no 6, and there is one on bank one, coil no 4 i think…..looks firmly attached, althougt it has aged…

Why on your picture there is another like red wire coming from harness to ground? I dont have that….
Maybe LCI model only has that?
Also I have on bank 2 like three different coil marks lol, Beru, bmw and boch is one….

[R Shaffner]

I see that there isn't another wire (brown or red) connected to the stud where the ground wire is connected. Are you saying you don't have a similar brown or red wire coming from from the coil pack harness that you can connect to the head? No wire at all? Are you sure?

The ground strap in your pic isn't doing anything like that. Serves no purpose that way. It's just connecting the head to itself.

The heads need a good ground. For the spark plugs, if nothing else. I'd look closely to see if there's a loose wire that's supposed to be connected to the head as a grounding wire.

If you can't find one (which would be odd), you could run your own ground wire from the body or the block to each head.

[Nicolemen]

Yeah, a bad or missing ground can definitely cause misfires, especially at idle. I agree with R Shaffner, if that strap on coil #6 is just going from the head to the head, it's not doing much — you need a real ground wire from the harness going to the head. Maybe it broke off or got lost over time. You could try running your own ground from the body or engine block to the head just to test if that clears things up.

[R Shaffner]

I should have suggested that you pull out a meter and test the continuity of the head to the block, and both to a good ground on the body. The head should also be grounded to the block via the head bolts, if nothing else. And the block to the body.

The ground strap from the block to the body might be the issue. If not, and you have good continuity from the head to the body, then the problem isn't from a bad ground connection, of course.

[Panamera1988]

Uff I will have to double check all the wires, although other people are saying my strap is fine, that brown wire is something not OEM....

[Panamera1988]

So I have checked both grounds and they are the same without the brown wire, but I see on your picture that brown wire is coming from coil rubber part and it has rubber exit, which in my case rubber on coils are without that. Maybe the brown wite is only on TU motor?

[R Shaffner]

Or perhaps US and European models are different. (I've seen the wire on US M62's as well.)

[Panamera1988]

I have seen two more and they dont have the brown wire….

Is it possible that faulty oxigen sensor causes idle misfire? Even there are no codes for oxigen sensor?

Also Im waiting for Oem(Bosch) Maf sensor, because I have Bremi now…

[R Shaffner]

I have seen two more and they dont have the brown wire….

Is it possible that faulty oxigen sensor causes idle misfire? Even there are no codes for oxigen sensor?

Also Im waiting for Oem(Bosch) Maf sensor, because I have Bremi now…

I don't know what a faulty O2 sensor might do. You could try unplugging one to see.

[Mayorchuck]

I believe the brown wire was used as a secondary ground. The wiring harness on yours must be a little different but the DME uses the black wire in the harness for the coil ground. I don't think that is your issue.

What codes are you getting? Is the entire bank reading misfires or just a single cylinder? If you have a good reader, an bad O2 sensor should throw a code. Unplugging the MAF runs the car in default, without considering the readings from those sensors. If you have one bank misfiring, I would suspect a clogged cat or a large vacuum leak on that side.

[Panamera1988]

The problem si bank 2
Codes are misfire cilinder 5 and 8, but mechanic said sometimes the whole bank but periodically.
And he said its not like real misfire but more like a half or unfinished cilinder ignition.
The cats are not the problem, because there were no cats when the problem started, then I have installed new ones but still the same…
The seals are new and vacum is 100%(smoke machine tested)
He thinks its a wire or dme problem( since there was water in Dme box, and some bad relays were replaced)

[Mayorchuck]

I would agree the water intrusion would make sense with the odd on and off misfires, especially if there was signs of water or corrosion on the DME pins.

[Panamera1988]

One thing I have is the same Dme from another m62, just have to make a clone and try to replace the one now inside