Engine Cutting Out / Loss of Power...Questions & Answers [and Pics]

[bmwman91]

This problem has cropped up recently.  On cold starts after running for maybe 2 minutes the motor would lose almost all power between 2000 and 3500RPM.  There were no misfires or loud noises, just a big dead-feeling when pressing the gas.  After a couple minutes it would go away and run great.  It seemed temperature dependent or something, and it did not toss fault codes at me.

This morning it started doing the same thing, except it did not go away and was REALLY bad.  I almost could not get the car home.  Then after it ran a little longer, it began running A-OK again.  I swapped cars to get to work though as I did not want to risk having issues on the highway.  A check engine light DID pop on for a second and disappeared the moment I let off the gas pedal this morning.

I paid close attention to the mileage needle during this and it was not hopping around or anything.  As I pressed the gas (with nothing much happening) it was steadily giving lower readings...the fuel system seems to be working just fine.  I have seen a few people here fix this with new ignition coils.  I have a COP kit installed, and I think the M54 motor coils I am using were new when I got them from another member.  Before I go replacing them does anyone have any other suggestions?

I have also been getting a steady check engine light here & there for code 1221 (oxygen sensor power).  I have a wideband system installed and there are NO problems with it or it would be tossing me fault codes.  It seems unrelated, probably due to some bypass wiring where the oxygen sensor heater relay used to be.

Thanks people!

[bmwman91]

Well, I dug around a little today.  Some time was spent on the factory repair manual we have available here in the Reference section.  It said that any oozing of the coil body's epoxy casing meant that immediate replacement was recommended.  Once I got home from work I nosed around under the hood.  No bad connections were anywhere to be found for my wide band O2 system, so unless there is some sort of internal fault in it, the CEL I get is due to something else.  Now, on to the more compelling evidence.....

I pulled the coils and thoroughly inspected them and their boots.  I also checked the spark plugs.  The plugs are maybe 18 months old, and were clean enough.  There was a lot of carbon buildup everywhere but at the electrodes, so they were fine (I got 4 new ones anyway just for when I need them).  The impedance on the plug boots checked out, and wiggling them did not cause a problem.  The impedance of the coils' primary coil checked out, and it was not shorting with the secondary coil circuit.  The connector wires were also all intact.

So, that leaves visible evidence on the coil bodies...maybe some sort of ooze?  Ooze...check!

This was the worst one.  Yeah, I don't think that was there when I got them.


A cropped shot at full resolution.  UGLY!


The damage does not need to be as awful as the first 2 pics.  Even this is looking pretty suspicious.  People with COP conversions, check the coils every 6 monbths or so.  I have been running these for roughly 2 years and maybe 25k miles.  I cannot remember of they were new or used when I got them.


Closer crop.


Looking at the bottom also shows some ooziness.  Either take a picture of your brand new ones, or remember how clean they were when new.  You will want to make sure there is not any oozing going on or replacement will be coming soon.


Closer for #3.


So, I HOPE this is the cause of my problems.  I test drove it after cleaning things up as best I could this evening.  The motor actually died trying to idle, regardless of pumping the gas.  It started right back up, luckily.  It seemed that going to WOT generally made the issue do away, but I only tried it in 2nd & 3rd gear where the RPM's rise fast enough that it gets out of the trouble spot quick enough.  Above 3500RPM, everything seems fine.  The WOT thing almost makes me think it is fuel system related (going to open-loop at WOT, ignoring the O2 sensor).

The one thing that REALLY pissed the car off was cruising at low-load in 5th gear.  I would keep my foot firmly in place on the gas, and the car would begin slowing down due to the engine mysteriously losing power.  Trying to idle after that led to severe stumbling, and it died once, almost twice.  The reason I do not think it is fuel-related is as follows.

I was having a similar issue 2 years ago or so.  The car would behave badly at part throttle.  The MPG needle would also jump all over the place, although there was no CEL being tossed.  It ended up being a pooped out AFM, which I replaced with my MAF conversion.  This current problem, where I get bogged at part throttle, does not effect the MPG needle.  It stays in place, or only moves slow & smooth as usual.  The MPG needle is a great thing, you can tell a lot from it!

So anyway, I had ordered a set of 8 of these coil packs from a wrecking yard (44k miles on them) from a V8 X5.  I suspected this was due to ignition coils and ordered them on a hunch before even looking.  They will arrive next week, and they will hopefully solve this annoying issue!  Sorry about the super long post, but I want to be as descriptive as possible.  I know others have had similar issues, so hopefully someone's search will lead them to this thing (goodness knows there are enough words to match lol).

Even if you have stock M42 ignition coils, if your car runs poorly and you cannot figure out why, visually inspect the coils.  The service manual for the stock ones is where I saw the warning about the ooze!

[bmwman91]

To add to the discussion, there is of course the "why" aspect.  Why have the coils vomited goo all over themselves?  Well, heat is the obvious answer.  There are 2 ways it can be getting too hot as far as I can tell.

One is the obvious one...their placement on the M42 somehow heats them up more than they were intended to be on M54 motors.  I find this somewhat unlikely.  They are well ventilated, and are not really in direct contact with the cylinder head.

The second one is electrical.  Perhaps the M42's Motronic drives these coils a little differently than the Motronic on newer BMW motors.  The dwell times might be longer, or SOMETHING, causing excessive heating of the secondary coils.  The apparent spark failure would seem to be due to internal arcing in the secondary coil, either to its own windings, or to the ferrous body that has melted epoxy all over it.

Then again, this might be part of their normal life cycle.  I do not know what the rated operating service life of these coils is.  This is probably how they all fail...eventually.  The question is whether it should happen as soon as it has or not.  If I had new coils, then this is a major problem.  If the member I got them from (who is, unfortunately, deceased) sent used ones then maybe this is no big deal.  Turner Motorsport was selling used ones for a very good price back when the COP conversion was developed, so who knows.

[colin86325]

Good info.  What brand name appears on your COPs?

Mine didn't have a name on them--I ordered from FCP Scrotum, and one of my coils failed within 500 miles.  I was not happy.  I've also noticed that the aluminum carrier to which the coils mount can become very hot. I think heat travels through the tang that extends between the engine and the firewall.  A heatshield could do the trick, or thermally insulated washers/standoffs for the coils.
Cooler operation equals longer operation when electronics are involved.

[bmwman91]

Good info.  What brand name appears on your COPs?

Mine didn't have a name on them--I ordered from FCP Scrotum, and one of my coils failed within 500 miles.  I was not happy.  I've also noticed that the aluminum carrier to which the coils mount can become very hot. I think heat travels through the tang that extends between the engine and the firewall.  A heatshield could do the trick, or thermally insulated washers/standoffs for the coils.
Cooler operation equals longer operation when electronics are involved.

These are Bremi coils, the OE substitute for Bosch.

I have been wondering about heat issues thanks to this.  One possible way to isolate the coils would be to move the bottom nuts down on the 2 mounting posts.  Then, to get the coils back to the proper height, some ceramic or heat resistant plastic spacers could go between the COP plate and coild packs.  This would create some air space below the coils, as well as eliminate like 90% of the surface contact between the plate and coil body.  That should help reduce the heat transfer pretty well.

The other big heat transfer spot is probably the rubber boot that fits so snugly in the plug hole.  Rubber is not a great conductor of heat, but being wedged firmly into the top of the head / valve cover with the bottom coil protrusion inside it has to get pretty hot.  There is nothing that can be done about that though, other than maybe finding a rubber boot with a smaller neck.

Oh and lol @ FCP Scrotum.

[ClodKing]

I ordered mine from FAP99.com

I've also noticed that the aluminum carrier to which the coils mount can become very hot. I think heat travels through the tang that extends between the engine and the firewall. A heatshield could do the trick, or thermally insulated washers/standoffs for the coils.

What about modifying the plastic dish that the old setup had?? Maybe just shaving off the plastic sides, shorten the tub walls, and reinstall.

I figure the pressure from the aluminum plate would hold the plastic tub in place.

That might also do nothing more then insulate the space between the plastic tub, and the aluminum plate... I don't know.

[mkodama]

I've also noticed that the aluminum carrier to which the coils mount can become very hot.

What do you mean by very hot?  I previously had a car with an M54 engine (has the same COP stock) and everything stays pretty cool as far as engines go.  Everything on top of the engine like intake manifold, plastic engine covers, valve covers, etc... would be hot, but you could still touch everything and work with the pieces if needed.

[EN318isPDX]

What do you mean by very hot?  I previously had a car with an M54 engine (has the same COP stock) and everything stays pretty cool as far as engines go.  Everything on top of the engine like intake manifold, plastic engine covers, valve covers, etc... would be hot, but you could still touch everything and work with the pieces if needed.

Nice sig.... lol i think there are better ones out there than that... that was you tryin to say that i never work on my car.

[mkodama]

Nice sig.... lol i think there are better ones out there than that... that was you tryin to say that i never work on my car.

Haha, that was from you arguing with tjts1 when he was saying a medium case differential was horrible for an e30 3-series

[bmwman91]

Alrighty...update.  The car SEEMS to run just fine now that I put in some "fresh" coils.  The used X5 V8 coils are working, and the car has not goofed on me yet.  The real test will be tomorrow morning when I do the "cold" morning start / commute.

I also installed these coils differently than the previous ones.  I moved the mounting plate down about 4mm on the threaded posts (moved the nuts down) and put 3 washers on each screw between the coil body and bracket.  This eliminates a lot of contact area, and provides an airspace below the coil.  I also used pan-head screws instead of countersunk ones.  The countersunk ones force the coil into an exact position, and being that nothing is perfect, misalignments with the plug holes will put large forces on the coil bodies.  This may have ended up pushing the plastic body into the metal core or something, and perhaps shortened the coils' lives.  Anyway, now the coils are more free to let themselves align naturally with the plug holes before cranking down the screws fully.

So, I suppose I should put out a Technical Service Bulletin (TSB) for people with the COP conversion.  The "fix" can be done with $4 worth of hardware from the local depot, and about 15 minutes.

=====================
I took the worst looking coil of the bunch and cut the 2 welds on its core.  Having seen the melted looking plastic, I was curious to see if there was some hole burned in it where the secondary wiring was arcing to the metal body or something.  Well, nothing that dramatic was present.  However, the fact that the body plastic was melted was a sure-fire indicator that the coil had gone south.

My guess as to why the car was pooping out is as follows.  Even ONE bad coil is all it takes.  One cylinder not firing shoots a bunch of raw gasoline into the exhaust stream.  This mixes with the exhaust from the other 3 cylinders, and then passes the oxygen sensor.  The oxygen sensor reads a severely lean mixture (it reads the amount of OXYGEN in the exhaust...and an uncombusted mixture still has tons of O2 in it), which signals the ECU to start dumping fuel in.  That is all it takes.  Having raw fuel jump through there will freak it out, and kill your catalyst real quick.

Anywho, picture time.

Here are both sides of the worst looking coil of the bunch.