Replace one ignition coil or all six?
 

On the 535i a CEL that keeps coming back (and this time here to stay) seems to be due to a weakening coil (car still gets 27mpg) highway. Perhaps this coil is the reason for a shaky idle. I'm not sure.

Shop called me. If I replace one coil, it's $180 with labor. Should I replace all six for $580 (with labor) preemptively?

Plugs were done 10k miles ago.

If I solve the basic algebra, that means they are charging $100 for labor (same for one or all six) and $80/coil. ECS has the BMW coils for $60 each. The mark-up is reasonable (and I don't have gear to check/clear CEL's and what not). I'm sure it's not a hard job.

Then again, they had a pretty decent price on the brake jobs (which is what the car is in for). Car is at 50k miles.

If your 5 is anything like an E46, you should DIY.

Pretty easy really.

True. But it's at the shop and they're generally a reasonable bunch. And if it continues to miss at idle, I can hold it over them.Get them to check the plug gaps etc (stuff I can't do).

I'd probably just do them all. Chances are if one is at EOL the remaining 5 are pretty close.

This. It's like 3 small bolts.

Lou: Seems unethical for me to complain about CEL & idle to the shop, they trace it to a coil and then I say, ok, I'll DIY it.

One solution would be to have them do the one and I do the five at home.

I think I'm just going to have them do it. This car has not been too expensive to buy or run.

:+1

I can't speak to the actual mechanic, just the guy on the phone. So I'm not sure if they "tested" that coil to be bad or just going of the CEL and the mechanic has a hunch (and he's been pretty ok).

Anyway, they are reasonable. I've been driving like this for 7k miles, I think I can weather another week or two. Turns out they were selling a $40 (ECS Tuning price) delphi coil at $80 to me, but they are also ok if I bring my own parts. I'll either do that or I'll DIY it. Might be harder on the n55 turbo compared to the m52/m54 series - strut bars may have to come off.

They should charge you a diagnostic fee. I wouldn't feel bad about paying for the diagnosis and doing the work myself. :dunno:

I have no idea how they identified a coil getting "weak." If they scanned the car and saw a misfire on one cylinder, that would indicate (likely) that the specific coil had failed. If it were my car, I'd replace all the coils at that point.

is this an n54 or n55?

Just curious from a rough idle diagnosis. N54s have leaky injectors, fuel pumps, carbon build up and plugs / coils as possible culprits. N55s less of those issues.

When I did coils, I did all 6 along with plugs. It is an easy, DIY, but it also seems like your indy is charging fairly, so it might just be worth it... especially if you're planning on holding on to it for a while.

2011 N55.

It could be plugs/adaptation, it could be injectors, it could indeed be the coils...

His labor at $100 is not bad. But his coil prices are high, so I think I'm going to DIY. They just pop in, it seems.

Do you guys use dielectric grease when you put in coils? Rubber on rubber?

I have never used dielectric grease on coils. then again I never used it on cars that had plug wires either.

I just had one fail... (well, John did) and I'm going to go all 6. Peace of mind.

Diagnostic fee is probably in the $120-150 range.

I wouldn't feel unethical at all. If anything, dealers should feel unethical for raping the many customers for charging exorbitant fees for work that a monkey can do.

My opinion, of course.

Yes, I have always used it - both when I had standard coil/distributor/leads as well as 'coil on plug'. Just a little bit keeps things going in easy and (I think) when it comes time to do it again in the future - easy off too.

And yes, I'd do all 6. I would be sure to use all the same brand/PN of coil - if you break up who is doing what. And - I would also do the same with the plugs and connectors as well.

I use dielectric grease when I push the rubber part into the spark plug itself. It makes it easier and provides good contact.

If using BMW replacement parts, make sure it is the "coil of the month" - BMW can't make up their mind which manufacturer they dislike least. Currently they are using Delphi coils. Here's the complete supersession history:


https://www.glaver.org/transient/8616153.png

Note: The part number carries a precaution that it contains hexahydro-4-methylphthalic anhydride which is apparently Not Good For You. This is a BMW AG warning, not a California Prop. 65 one, so possibly for real. Do not eat. :rolleyes:

Thanks, Terry. My research indicated that the coil du jour was Delphi as well. That was also what my mechanic was going to use.

Last night I ordered a six-pack of Delphi on FCP Euro. The site says it fits my car. They were so reasonable in price $155 for all six, I'm suspicious that there is 'delphi' and there is 'delphi'.

https://www.fcpeuro.com/products/bmw...12138616153kt1

At that price, it can't hurt (given that it's looking easy and I'm going to DIY).

Do you have a garage / workshop at your new(ish) place? If not, do you want to come over here to work on it? I'm pretty sure I have the right size spark plug wrench, as well as all of the usual tools. Just let me know - I'm working on the Sat/Sun overnight, so those days are out. And I need some warning to have my tenant move some of his cars (AKA "clown car" and "rustbucket") so you can get into the garage.

Thank you so much, Terry.

I have parking spots but no garage spacious or lit enough to work in. Well, one spot is, but the queen boxster lives there :).

Since I'm not doing plugs (they are only 10k old), I thought I could do the coils on the street or in my driveway. Is that too optimistic (or ghetto)? Everyone made it sound so easy.

It should be easy - just take the plastic cover off to access the coil packs. I tend to not want to do things on the street because that just temps fate with some silly little thing you need and don't have, and of course the car is apart.

Here are the instructions (for an E46, but the only difference is how much of the cabin microfilter housing you need to remove to get to the rear part of the engine cover): https://www.glaver.org/transient/coils.pdf

Give me or Sue a call here if yu run into anything - we can at least roll w/ instructions, tools, and parts.

This exact scenario played out a few months ago when I swapping the steering wheel of the 535i. I broke a small wire connection and the car was on the street right in front of my living room. The car without a steering wheel sat there for about a day. Our town has no street cleaning though. Which means there is the occasional carcass (;)) or eccentric car that never moves.

It should be a 20 min job roadside or in a parking spot without issue. The only tool needed is a socket to remove the engine cover. The coil latches swing open (be sure you swing them all the way vertical) and disconnect. There is a hole in the latch to put your finger through and pull them out. The plastic at the hole is a little sharp, so you may want some light gloves or a rag to displace the load a bit. pop the new ones in (be sure the rubber sleeve doesn't bunch at the top of the opening, snap the latch down and you're done. (at least that was how it was on the n54).

Did the DIY. I had some other stuff going on, so it took the better part of a day on and off. Total time spent, way more than an hour, probably two. Next time around, maybe 30-40 minutes, done carefully, but definitely not roadside work. Some cables/harnesses to unclip and move around. Turbo intakes all running on top etc. Coils themselves were relatively easy to pop in and out. Access? Not so much. I think part of the problem was that there was exactly zero write-ups/DIY's to follow for the f10 platform. Only for e90 and f30 with the same engine. So I had to remove as I went and figure it out.

Anyway, it does feel a bit better, still a slight idle shake but dare I say it, car feels smoother and stronger 2 to 4k rpm, i.e. under load. We will see if the CEL comes back.

Wow - that is a TON more stuff in the way than I would have thought.

Nicely done!

Update. The idle shake came back. CEL (misfire cyl.3) was gone for a while but recently came back and stayed on. Idle shake got a bit worse. So off to the mechanic...

Lo & behold, spark plug #3 was bad. They gave me a high price of labor for all six instead of just one, so I just got that one done. He wanted $120 for the diagnosis & labor of the bad one, fair. But $300 for doing all six. What?

In retrospect... I was basically "in there" for all six when I was doing the coils. Having never done plugs, and with no one around who had the "feel" for it, I did not feel confident I had the mechanical feel and I got paranoid about engine threads. I have many destroyed threads in my history, don't need to add a BMW N55 to that list. I do have a torque wrench for wheels, not sure if it would apply to plugs, and I think I'd need to get a socket for plugs. Next time...

The other lesson was that I "over-relied" on the service history. Plugs were done at 41k at an indie just before my purchase. By 45k, the car already had idle shake. So I suspected coils etc. I did the coils just before 50k, here we are at 52k and finally reaching the culprit. So I lived with a bad plug for more than a year and 8k miles. :ack: The symptoms seemed to be contained to idle rpm, car still got 27mpg on the highway, but now that the plug is done, the butt dyno says +10% in mid-range. Hope the shakes and misfires didn't do any mechanical damage. Just tired the engine mounts, perhaps.