M54 Cold-start misfire

[jduffett]

I have a 2002 E39 M54 with a persistent cold-start misfire on cylinder #5. Symptoms are as follows:

• Misfire on cold start (cylinder #5) w/fuel shutoff: can hear/feel the misfire prior to the fault being set. Fault code set is P1351.
• Allowing the car to "warm up" for a period of time, and then either clearing codes or shutting the engine off and restarting results in no subsequent misfire or fault codes, and it runs well (normal). "Warm up" time seems to be mostly be related to ambient temperature/underhood temperature than coolant or oil temps. Warm-up time required ranges from ~30 sec at 10ºC, to 1-2 minutes at ~0ºC, to ~10 minutes at -10ºC. 15ºC and warmer it doesn't occur at all.
• If I clear codes and begin driving before the required warm up period has elapsed, I can observe that the frequency of misfiring does decrease somewhat as you approach that critical time/temperature.
• "Warm" restart results in no misfire. Again, definition of warm has more to do with underhood temp it seems.
• If I do not clear codes, but restart when warmed to reset the fuel cutoff, some other fault codes will sometimes be set during that warmup period: P1346 (misfire during start cylinder 3); P0300 (random/multiple cylinder misfire); P1349 (misfire cylinder 4 with fuel cut-off); P0174 (system too lean bank 2 - pending only, and pretty infrequent); P0172 (system too rich bank 1 - pending only, and only ever saw this once). I've also seen P0313 (misfire with low fuel), but I was legitimately low on fuel, and if I understand this code correctly this should be irrelevant given that the misfire conditions occur with and without low tank level.

Some background on the car: It is a 2002 525iT with ~305k KM (191k miles). Last winter I burned a valve, and put in an M54b30. The donor was an E46 330 with ~35k miles, and was supposed to be a ZHP (or Canadian ZHP equivalent), though I don't have any proof of that. Swap was done with all 3.0 intake including proper MS43 530 MAF (donor was MS45.1), and I used the later push-in coils with the triangular plugs, along with the appropriate valve cover and late E39 ignition wiring harness. DME flashed to 530i. I put about 5k km on this last winter with no issues, until about March, when it seems I had the dreaded catastrophic CCV failure (used the parts from the donor since they were low mileage; bad idea apparently!). It seems I got "lucky" with this, as it seems I did "hydrolock" on oil, but it happened a low load/speed, and after cleaning all the oil out / burning it off, and replacing all the CCV components, it ran fine! I have put about 15k km on it since then, and through the summer it generally ran great, but beginning in the fall as the temperatures dropped, this misfire thing began.

So, here's what I've done so far:

• All new coils
• All new plugs
• Changed oil; no sign of coolant
• Warm compression test: ~185psi on all cylinders
• Cold compression test: 185psi on #5 (didn't test others cold)
• Visual inspection on #5 and #2 (for comparison) with borescope (both look carbon-y - black and bumpy; no sign of moisture on #5, but couldn't see edges)
• Swapped injector from 5 to 1; replaced all injector o-rings
• Replaced valve cover + gasket and grommets (crack in old VC; gasket brittle)
• Replaced IM gaskets + o-rings on air dist & temp sensor + TB gasket (all looked fine; temp sensor (old ring and new) didn't feel that tight in hole)
• Replaced DISA valve (old was reasonably snug fit, and looked okay other than tear in seal on the straight section)
• Replaced SAP vac hoses (one from check valve to solenoid was brittle)
• Replaced vacuum caps (one had some cracking)
• Inspected TB boots; other vac hoses underhood; no defects found
• Checked brake booster by disconnecting and capping port (no change)
• Replaced fuel filter
• CCV: why #5? Changed in March 2016; all components look okay (including dipstick tube looks clear); did not disassembly CCV from IM or disconnect lines at the CCV (probably should have done this when I had the IM off I guess)

I'm starting to run out of ideas... My thoughts for further troubleshooting:

• HVAs/hydraulic lifters: compression is good; any other way to test?
• Vacuum leak: most replace/inspected/disturbed above, particularly relating to #5. Anything I'm missing?
• VANOS: Can’t see why #5 specifically; anything I should be testing here?
• Crank or cam sensor? MAF? Fuel pump? Again, why #5?
• Since it is temp related, temp sensors? All match ambient when cold, and have normal readings when warm. T-stat? Warm idle (after drive to work) coolant temp is 91deg C (falls in 88-95 range). Suspect no issue.

Anybody have any thoughts??

[bmwdirtracer]

You've made an extraordinarily thorough post - thank you.

I actually have a very similar issue on my own M5, which has frustrated me greatly. There's a concurrent thread (mine)called "DME repair" on this. You'll find the factory S.I.B. in that post for the lifters.

And that's what I'd guess is your issue.

Do a leak down test, engine cold. On my own engine, compression was just fine, but one of the misfiring cylinders showed 25% leakdown past the intake valves.

[jduffett]

Thanks Chris! I would never have looked in your thread based on the title, but there are definitely some similarities there! I'd read about lifter problems and the SIB, and they were one of my first hunches, but I moved on from that based on the level of effort to get to them, particularly after the compression test looked fine. My symptoms match the SIB, but I'm not really sure I understand the mechanism of failure here - if the engine was running fine when shut off, how does the lifter get hyper-extended? I can see how they'd eventually collapse as the oil drains out of them. The relation to temperature is also curious - I'd kind of expect any temp related lifter issue to be related to oil temperature (either viscosity, or change in volume), but the issue goes away long before the oil has warmed appreciably. This is what led me down the vacuum leak path - I was picturing cold intake gaskets and manifold contracting and creating a leak path that seals up once underhood temps rise. If I read correctly, your misfires occur once warm? In any case, you're probably right, a leak down test would probably be a good next move. Your comments in your thread regarding bent valves certainly got me thinking, particularly in the context of my "hydrolock" near-miss... That's probably my worst fear, but I really can't see how that would be a temp related thing.

It make be a while before I report back with the results of the leak down test, but I will follow up for sure, and in the mean time I'll be watching your thread with interest too!

Thanks again!

John

[bmwdirtracer]

My car's misfires occurred cold or warm, more when cold. However, cylinder 2 misfired twice as much on the cold morning drive; cylinder 8 misfired 5-10 times as much on the warmer afternoon trek. I cannot begin to explain why, but, like you, I was running out of possibilities. As you saw in that thread, I have many erudite friends here, , and one of them led me to the SIB. I read through that, really not believing there was an answer there, until the last couple of paragraphs. Even then, I had serious doubts, because the engine passed compression tests . But when I found one of the two cylinders had a leakdown of 25%, I followed that lead.

Please do note, though, that there's some likelihood that my cylinder 2 excessive leakdown and misfire has been caused by carbon deposits on the valve, since it seems I've corrected the leakdown with a damned hammer! I never would have believed that....still don't, until I see the engine running without misfires, again.

Still, you'll see that you are not alone, in your frustration. Many of the friends on my thread are incredibly experienced, exceptionally knowledgeable. And sometimes, correct solutions are hard to find, even with the best resources. (I've got ISTA, Autologic, Launch, smoke machines, fuel pressure tester, compression tester, leak down tester, the ability to count each misfire on each cylinder, watch cylinder balance, plus several Master Techs, a "Premier Master Tech" boss, and a number of similarly knowledgeable friends who have given great inputs, and generally made sure I wasn't missing something.)



For you, the leak down test should be next. Do this with engine stone cold, because that's when your problem arises.

[jduffett]

Warm leakdown results:

#1: 1%
#5: 4%
#3: 2%
#6: 1%
#2: 2%
#4: 5%

No appreciable indication of leakage through intake or exhaust; could feel/hear leakage from oil filler for #4 & #5. Now that I've got that baseline, and got the car prepped to do this quickly, I'm gonna roll it outside and leave it for the night. Supposed to be -15°C overnight, so that should be plenty cold!

[jduffett]

Cold leakdown results:

#1: 0%
#5: 3%
#3: 2%
#6: 1%
#2: 4%
#4: 3%

This seems good, but it doesn't really point me anywhere for the misfire issue!

[bmwdirtracer]

Again, congratulations on being so thorough! And for surviving negative 15 degree temps....I'm about dying, right now, at +13 degrees! (Dammit, I want to move back to Maui)

Your thoroughness rules out most things, but I can see a potential hole or two.

In spite of the fact you've replaced everything vacuum related, the smoke test is missing. That's likely extremely difficult, where you are....but what if there's a crack in the intake manifold runner for cylinder 5?

Also, I'd recommend that you clean the injector electrical plug and coil electrical plug for #5. Make sure that the pins of the connector don't slide back when you push them, either. Similarly, unplug all the connectors at the DME, and clean both sides of each connection with electrical contact cleaner.

Inspect the coil gang ground in the coil wiring rail - there's a resistor there, and all the coils join in a "sonic weld" ( a big soldered joint), where one wire might be cracking away from a good connection. This would certainly happen more when cold, before the metal expands.

[jduffett]

In spite of the fact you've replaced everything vacuum related, the smoke test is missing. That's likely extremely difficult, where you are....but what if there's a crack in the intake manifold runner for cylinder 5?

Possible... I did look the manifold over while I had it off, though it is quite possible I could have missed a crack, especially if it's the sort of thing that opens or closes based on a temp change. And in general, yes, point taken on the smoke test. I did make an attempt at a DIY smoke test, but it didn't work out so well and was a pretty miserable kind of thing to be trying to do outside in the cold.

Also, I'd recommend that you clean the injector electrical plug and coil electrical plug for #5. Make sure that the pins of the connector don't slide back when you push them, either. Similarly, unplug all the connectors at the DME, and clean both sides of each connection with electrical contact cleaner.

Inspect the coil gang ground in the coil wiring rail - there's a resistor there, and all the coils join in a "sonic weld" ( a big soldered joint), where one wire might be cracking away from a good connection. This would certainly happen more when cold, before the metal expands.

I think I can rule out a big chunk of this as well. I must have missed it in my list, but I had been running the E46 ignition harness from the donor. Part way through this process I swapped that out for a new E39 ignition harness (had it already, just hadn't gotten around to doing it). Both of these by the way had a newer style 2-pin connector, so both had the old connector spliced in. Two different harnesses with that connector soldered by two different people, with the same end result (and it used to run fine with the E46 one), so I strongly doubt there's anything there, but I figured I'd mention it for completeness. On your list, that only really leaves the DME and DME contacts. Worth a look I guess!

The other thing I've been thinking about is whether there's anything special about #5... The only thing I've really come up with is the CCV connection between 5 & 6. I'm not sure if there's any good reason why a leak there would be more likely to affect #5 than #6. I did disconnect this and reconnect when I had the manifold off, and didn't note anything unusual. Given the parts are relatively new, how reliable are those connections typically? I can't say I really like the feel of them in comparison to a hose and hose clamp!

[synrgy350]

Did you ever find a solution to this? I'm also experiencing the same issues on my 525i. Thanks!

[ross1]

I had a similar cold misfire on an M52 which turned out to be a plug and it's lead marinating in engine oil from a failed seal on the valve cover. A fresh gasket cured it.
When the cold misfire would occur(not always)it would often go away if stopped and re-started. Ostensibly the DME shut had off fuel after detecting the misfire and tried fueling again with the subsequent re-start.
I never could figure out why it was intermittent.
Maybe have a look into the plug well for your effected cylinder, easy and free to do.
Good luck

[jduffett]

Update: I've done little troubleshooting since my last post, and have been away or just dealing with it... New interesting info from today though!

Started car at -5C this morning, misfired, warmed up, cleared codes, and drove an hour and a half. Parked car for an hour at -7C, then restarted. Misfired to begin with, but not enough to set fault code. It was still warm enough that it went closed loop almost right away though, which meant I could monitor fuel trims. Normally, it misfires on cold start until around the time it goes closed loop, at which point the fuel trims can compensate, and it trends towards normal, but in this case it showed short term fuel trim on bank 2 starting at 26%, then tapered down to less than 10% (and stops misfiring as well). So that tends to support the idea that I have a vacuum leak when the car is cold that seals up as it warms up. Somewhere that primarily affects cylinder 5... That's only ~17s to go from ~26% to <10% though, which seems awfully fast for something leaking to heat up and seal... Seems more like a state change to me.

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[bmwdirtracer]

Given that latest info, I'd have to suggest having the programming / software updated, as well as a pro smoke test. And, when's the last time your fuel filter was changed? The filter includes the pressure regulator; common failure on an E39. For a single cylinder, injector o-ring or manifold gasket is questionable....which brings us back to the smoke test.....

[jduffett]

Long time no update... As you can probably guess, the weather warmed up, and my opportunities and motivation to troubleshoot went away... Now that the cold weather is here, my #5 misfire is back. I'm also now randomly (not temp related) getting #6 misfire, accompanied by a code for #6 injector circuit. Dropped the car off with my mechanic last week, and so far all he has been able to do is confirm my troubleshooting results - smoke test shows no vac leaks, confirmed not an injector or coil issue... Regarding the fuel filter, I did replace that as part of my troubleshooting last winter. It was the original, but it didn't make any noticeable difference. I just ordered a new DME, pre-coded with my VIN + 530i and with EWS bypassed, so it should be basically plug-and-play for troubleshooting purposes. Expensive way to troubleshoot without having a confirmed diagnosis, but at this point it seems like my next-best move. Should have results by the end of the week hopefully!

[jduffett]

Victory!
Thanks to Paterick @ Locke St Tire for the diagnostic work, and Kevin @ www.rpmmotorsport.net for the quick turnaround on the DME!

[rbelton]

How does this cold start sound?




link: https://youtu.be/lxDmbGWeSQ0