Sporadic Ghost Misfires - Please help me with these demons!

[Spinnerman]

2003 525i. Love the car. We've had it for a year and a half now I guess. Runs great with the exception of occasional misfires that go away as soon as you turn the car off and restart it. Usually this occurs upon cold start...the car with shudder a bit, we'll turn the car off and restart and we're golden. It can go 2-3 months without occurring and usually at least a month but it's still happening. Every time this happens the SES light will come on and then go off as soon as we restart the car. I have run codes almost every time this happens and it's always a misfire on one or two cylinders it's usually a different cylinder(s), rarely the same one(s) back-to-back.

When we bough the car we had it gone through by a very reputable shop and after this happened the first time I replaced plugs and coils and at the time no oil in plug tubes and the plugs and coils didn;t look that bad but they were all replaced with new Bosch stuff anyway.

As mentioned this almost always occurs during startup but the other day my wife says it happened on the freeway, all of a sudden it the car would shudder unless she sped up a little and then it was fine again and sputtered as she slowed down. She pulled over and restarted and just like always, the SES light went off and the car ran great rest of day and today. Just got back from reading codes and it says F1 and F2 (misfires on #5 and #6).

Please baby New Year help me figure this one out! :-) Next step is to have it looked over again but my assumption is that it's going to be tough to diagnose if it's not happening at the shop and it can go months between episodes.

Thanks much in advance for any and all guidance!!!

GS

[JimLev]

Welcome to the forum spinnerman.
I guess the first 2 things I'd check would be the fuel pressure and find out if you have any vacuum leaks.
The fuel pressure might not show much unless you could see what it is reading when it misfires.
A smoke test will show any vacuum leaks.
Maybe swap some injectors around.

[Spinnerman]

Thanks for the reply JimLev.

I've probably pulled the code(s) on this issue after it has occurred maybe 5 or 6 times. If the codes pointed to the same one or two cylinders each time then I could focus on those cylinders. Unfortunately it's different cylinders each time. I will look into fuel pressure and vacuum leaks. At this point I'll look at anything! The randomness of this issue, to me, seems to point to an electrical problem but that's just a non-educated assumption.

[JimLev]

If it's different cylinders it could be related to marginal fuel pressure and/or vac leaks.

[mattmar1]

If it's different cylinders it could be related to marginal fuel pressure and/or vac leaks.

Jim is dead on in what to look for. intermittents can be a beech to figure out. does the weather at the time tend to make any difference (rain, cold snap). random misfires tend to be either vac or fuel related. how many miles on the car? are the fuel filter, pump original? getting the P codes can give a bit more info vs the peake codes, they tend to be more specific (such as cylinder X with fuel cut off). that the problem started as a cold start issue leads one to think of a vac leak, this is where a smoke test can be very valuable.

[Spinnerman]

Doesn't seem to be outside temperature related. 150K miles on the car. Not sure if pump and filter are original. Again, the fact that the issue occurs then is fine for extended periods of time is what has prevented me from looking at some of the things mentioned but I am going to start to look at everything.

[geargrinder]

Ideally scan w/ BMW compatible tools. Peake almost doesn't count, that's technology from a previous era of ECU.... PeePee codes are WORSE than BMW codes for sure, less specific and if you use proper gear, the BMW codes come with a load of extra data - RPM when occurred, how many times occurred, engine temp when occurred etc. etc.

M54 engines have a whole checklist of potential misfire things to work down. If indeed its wandering around then of course that helps point you away from ignition or injectors (which would be more specific cylinders at least at first...) Things mentioned but also things like bad wiring or components on the sensor side - O2's, MAF's... if those are just starting to fail intermittently you easily could get this. Smoke test for vac leaks is ideal but most guys don't have access to that.

[Spinnerman]

Thanks for the reply geargrinder.

Are there any BMW compatible scanners out there that us casual DIY at home guys m ight be able to afford? Can you recoomend any?

GS

[geargrinder]

This is a FAQ for sure (I'm sure there are multiple "FAQ" answers written over the years) .

Short answer is, several options, the mainstream ones are:
- Get a cheap BMW K+DCAN cable from ebay and load "Mike's Easy BMW" package for free... this is old obsolete factory software but works wonders on the old chassis. Not the most friendly. Also allows you to try recoding if youre brave.
- Buy a handheld like a Creator or a Foxwell. Pretty friendly to use and portable as well. Doesn't allow extensive recoding but sure is convenient - no computer or cable messing around. I think the Creator BMW model is 310 and Foxwell is 510 but don't hold me to it...

Beyond that there is:
- PASoft "BMW Scanner" cable/software packages from eBay (these are all bootleg copies of older obsolete versions of the software but tend to work fine). Can do dangerous recoding things, sometimes has errors.
- Bigger more deluxe "Rheingold" packages which are the older versions of dealer software. Does dealer-safe type recoding.

For cheap and easy and idiot proof its hard to argue with the handhelds.

[Spinnerman]

Many thx again for the info. Will follow up when we figure this out.

GS

[Spinnerman]

OK...picked up a Creator reader but unless I was doing something wrong it didn't give me any more info that my Peake reader. The sporadic misfire issue occurred multiple times now so I parked it in the garage and made an appt for my BMW guy to look it over on the 14th. In the meantime I thought I'd look around the engine a little bit and noticed oil was leaking out of the oil filter housing. When the car was running it was coming out pretty good so I ran down and picked up a new Mann filter and O-ring which stopped the leak. The car was not misfiring now. It is possible that a bad oil filter housing gasket could allow enough air to get in to cause misfires?

BMW guy says smoke test revealed a valve cover to breather pipe leak which he replaced and a small leak at brake line check valve. Got it back and no misfires since but only time will tell. There are a number of other things my mechanic says it needs:
- Water tubes under intake manifold leaking coolant
- Valve cover gasket small leak
- Oil filter housing gasket leaking

These three items look like they're going to run over a $1000 to fix and I'll have him replace PCV stuff while he has it apart. Hopefully to misfire thing is at least fixed for good! :-)

[mattmar1]

coolant leak under the manifold, the plastic water pipes, happens on these cars, the pipes dont last forever. valve cover gasket, besides showing an oil leak, is also a vac leak. the OFHG is another weak spot on these cars. Valve cover pipe is a strong vac leak, good thing he replaced it. having him replace the rest of the CCV (PCV) pipes is good, the one that goes down to the dipstick is another common failure. Creator 310 isnt a bad tool at all, learning to use it will save you a lot on maintenance, and give you better grounding when talking to mechanics.

[jicaino]

Also if it's a sporadic thing you might want to replace the coils around (remove the coils from the sporadic misfiring cyl and replace it in another cyl) and see if fails follow the coil.

[Spinnerman]

All coils are brand new and the misfires have been multiple cylinders.

[jicaino]

Do we know condition of cat(s) ?

[Spinnerman]

I don't know how to assess the cats but as mentioned earlier, I had a smoke test done which revealed a few vac leaks that were repaired and I had a fairly major failure of my oil filter gasket. With all those things repaired it's been running well so far. Hopefully this has the misfires fixed but time will tell and I will revisit this thread if not. My main puzzler all along was the sporadic nature of the misfires....once every few months or so. Here's hoping it never returns :-)

Thanks for all replies!

GS