M50 spark plug / timing questions

[ProZak]

OK, had her for a couple of weeks and am beginning to get a feel for the car. Too sweet.

Power delivery seems to be less smooth than I'd expect, especially under WOT. Also, with cheap gas I'm getting some mild pinging on 50% or more throttle at lower RPMs (while accelerating). The anti-knock sensor seems to be doing a pretty good job, but I'd expect with a factory chip to be able to run 87 octane (I'm in the US) without pinging. Maybe not. Anyway, I'm thinking new spark plugs (I'm at ~113,000 miles right now) and need a good source for bone-stock OEM Bosch plugs, F7LDCRs if their website is to be believed. So, my question - what's the maintenance interval on those? Also, is replacement straightforward? I'm expecting something simple like

(1) remove engine cover
(2) pull (and label) plug wires
(3) pull old plugs, check for obvious issues (don't expect to see anything but normal wear, haven't used a drop of oil yet)
(4) insert new plugs
(5) torque to spec (what, by the way, is spec?)
(6) plug in wires
(7) start engine, listen for problems
(8) replace cover
(9) close hood
(10) drive.

Any gotchas? Anything else I should replace / check while I'm in there?

Finally, I was idly wondering if the cams on this engine are belt- or chain-driven, and if there was a service interval I needed to worry about. (Along similar lines, is it a VANOS motor? The BMW salesman (bought it at BMW of Nashville) said it was, and I don't have any reason to distrust him except for the fact that he's a salesman and I hadn't yet bought the car.)

Thanks a million in advance for your collective expertise, and thanks as well for the enlightening (Hah, a pun!) HID thread, as well as the hilarious photo stance thread. This site rules.

-Zak-

[Kalevera]

The M50tu requires premium fuel. I think the spec is 91 or something similar -- check the owner's manual. Don't run 87, that's just stupid.

30,000 miles on the plugs, or every inspection II.

The M50tu has vanos and has twin chains, with one between the dual cams.

best, whit

[ProZak]

The M50tu requires premium fuel. I think the spec is 91 or something similar -- check the owner's manual. Don't run 87, that's just stupid.

Fair enough, I'll double-check. Although in my defense, I do stick to Shell (a la the whole toptierfuel.com thing, whether it's legit or not). FWIW, most recent tank I ran 89 which seemed to help quite a bit.



30,000 miles on the plugs, or every inspection II.


Good deal, so I'm coming right up on it, assuming the PO kept up. Didn't have any maintenance records, so I'm flying blind for the first little while. I'll go ahead and do it this week, then.



The M50tu has vanos and has twin chains, with one between the dual cams.

best, whit

I'm reading that to mean that it's a lifetime item, and I don't have to worry about breaking belts / mashing valves / much gnashing of teeth and spending of money. Thanks. Also, FWIW, I was hoping to hear from you in this thread; I find your contributions here to be very enlightening, and I greatly appreciate your input.

-Zak-

[mjfeeney4]

If this is your first time changing plugs, you'll notice that each has a coil which contacts the top of the spark plug via a rubber "boot"

If you notice oil around the bottom of the plug well, then it is time to replace the valve cover gasket(s). In addition to replacing the large gasket there are also two doughnut shaped gasets which should be replaced. The gaskets become brittle with age and can cause oil to seep into the spark plug wells.

[ProZak]

Thanks for the tip! Does that mean that this engine is direct-coil ignition?

Last valve cover gasket I did was on a 1977 Chevy Caprice Classic, about 15 years ago, but it was pretty straightforward. Hopefully it won't be an issue; I've been checking the oil at every fillup and it hasn't moved a bit on the dipstick.

[dacoyote]

Thanks for the tip! Does that mean that this engine is direct-coil ignition?

Yes....

Also... I would check just for the fun of it.... if you start shorting out the coils (Like it will if she is leaking) it can get to be a very expensive repair really quick.

[ProZak]

Oh, I bet. I'll definitely take the time to check. I'm hoping the wells aren't too deep and a quick glance with a good flashlight is all it'll take.

[dacoyote]

Oh, I bet. I'll definitely take the time to check. I'm hoping the wells aren't too deep and a quick glance with a good flashlight is all it'll take.

Yeah... checking will be.

Open Hood (NS)
Pull the two 10mm nuts from the cover (they are under the little round covers)
Take off the oil cap and lift the cover
Pull a couple of the coils (still 10mm bolts)
Take a flash Light and look
Put the car back together.

You cannot see into the wells deep enough to not pull a coil unless it's over flowing with oil

[632 Regal]

be real careful with the coilpacks so you dont strip the studs out!!! do it when its cold.

[dacoyote]

be real careful with the coilpacks so you dont strip the studs out!!! do it when its cold.

what fun is that....

[Qsilver7]

perhaps a diagram of the ignition coil/spark plug might be of interest: http://www.realoem.com/bmw/showparts.do?model=HD63&mospid=47404&btnr=12_0425&hg=12&fg=05

and a diagram of the cylinder head cover that shows were all the capnuts are, grounding straps, and the profile gaskets: http://www.realoem.com/bmw/showparts.do?model=HD63&mospid=47404&btnr=11_1283&hg=11&fg=15

[ProZak]

Heh. Having scorched my fair share of body parts on hot engine bits in the past, I'll be sure to wait until morning. :D

[ProZak]

Thank you very much - good stuff.

[Guapo]

If changin out the valve cover gaskets, be SUPER careful with the valve cover studs. I broke one removing it .. snapped right off in my 1/4" drive wrench, and broke another when installing, not even close to tq spec.

Might want to consider having at least a couple sets on hand just in case.

[ProZak]

If changin out the valve cover gaskets, be SUPER careful with the valve cover studs. I broke one removing it .. snapped right off in my 1/4" drive wrench, and broke another when installing, not even close to tq spec.

Might want to consider having at least a couple sets on hand just in case.
Thanks. Hopefully, I won't have to do the gaskets this time around, but I'll keep that in mind. Do they get brittle from heat, or something silly like that?

[R1daveg]

Not sure if age/heat is the reason (but sounds logical for a >10 yo motor) but will add i broke one when removing, as there was a stuff on the thread which i did not clean off first...