2002 bmw 325xi awd Misfire

[Tank151]

I have a 2002 bmw 325xi awd. Check light popped on. Cylinder misfire. Decided to change all 6 plugs and all 6 coils. Noticed plug 6 have some oil on it. More than the rest. Started the car and it still idles rough and it won’t idle by its self I have to hold the throttle. Can anyone help? Please.

[Sleepyhead97]

Unplug the maf

[Tank151]

i unplugged the maf sensor and that did stop the stalling, thank you for that. that will be replaced this weekend. but it is still idling rough, again i've replaced the plugs and coils.

[Sleepyhead97]

Awesome glad that worked. It's something sensor related probably maf. It's going to run poorly until the bad sensor is replaced. Good luck!

[328 Power 04]

Please stop with poor advice. Unplugging the MAF just puts the engine ecu in default prewritten settings.

This can make you think it's the maf, but when in reality you may have a huge gaping hole in the intake boots causing vacuum leaks (way more common).

A proper diagnosis is more than just unplugging the MAF.

[Sleepyhead97]

It stopped car from stalling. Can drive it now. That's an improvement. Beyond that, it's likley sensor related likely the maf. Assuming all vacuum leaks fixed

[shadowpuck]

No. Abel is right. Unplugging the Maf does not mean the maf is bad.
Further diagnosis needs to be done.
Also - running the car without the Maf is not a very good idea.

[Sleepyhead97]

You both are right, and I know that. Just saying, the car is not stalling now, and an unplugged maf for a week is not going to hurt anything. Yes I recommend taking to a mechanic that knows what they are doing, but my advice got the car not to stall. Isn't it freezing up there?

[MarcoZandrini]

Have the intake system smoke tested to find ALL of the leaks. Unplugging the MAF forced the DME to use an overly rich fuel/air mixture. That masks the vacuum leaks.

[bmwdirtracer]

Wow....what happened to my post?

Smoke test is first. running car with MAF unplugged more than for testing is BAD.

Find the problem, THEN fix it. Masking the problem is entirely counterproductive, and will kill the very expensive cats, by the way.

[MIKYZZ4]

The cats can be very expensive!
Unplugging the MAF is just meant as a TEST, nothing more!
Check for intake leaks!

[Tank151]

UPDATE: i ended up replacing the maf sensor thinking maybe it could be that, when unplugged, car idled, rough but it idled. plugged sensor in and the car instantly shut down, upon restarting, it started than shut down again. i am going to schedule a smoke test at my local mechanics shop. sadly i will have to drive i there with maf unplugged, unless someone can suggest a at home smoke test?

[MIKYZZ4]

You can try checking all rubber intake boots and hoses for cracks and leaks-replace if any found.

[shadowpuck]

unless its a long, long drive - a quick trip to the shop with the MAF unplugged is ok, imho. obviously, you have to get the car to the shop. what we wanted to caution against (because we see it regularly on forums) is the temptation to drive with the MAF unplugged "just for a while" because removing the MAF from the engine's fueling strategy forces it to run in default/rich mode and that masks the real issue as well as damages downstream components if done long enough.

make sure it's a good BMW shop that has experience working with BMWs - and, let them diagnose the problem even though we've given you some diagnostic suggestions - they'll have the car in front of them; we do not have that luxury.

[Tank151]

Apt is set for a smoke test tomorrow, the shop is about a mile from my house. They have done bmws in the past so hopefully they can tell me the issue because I really want to drive it instead of letting it sit in the garage.

[GriffX5]

Before doing any of that I would clean the MAF. Then I would swap coils and see if the misfire moves before replacing any coils assuming you still had this issue after cleaning the MAF.
Cyl misfire doesn't mean the coil pack is bad it means the ECU didn't let it that coil fire because he is reading bad data. Find the source of the bad data.

[Tank151]

Maf is brand new, all coils and plugs are also brand new, just replaced them all.

[bmwdirtracer]

Before doing any of that I would clean the MAF. Then I would swap coils and see if the misfire moves before replacing any coils assuming you still had this issue after cleaning the MAF.
Cyl misfire doesn't mean the coil pack is bad it means the ECU didn't let it that coil fire because he is reading bad data. Find the source of the bad data.

No, actually, pretty much your entire post is in error.
Tank already replaced the MAF, not a good idea as all the techs here said, but it's done, so cleaning it will not help.
Tank also replaced all the coils and plugs, so swapping them is silly.

You've got to read the thread before responding.

But most of all: The DME does not refuse to fire the coil when it sees a problem: it refuses to fire the injector, because it's the unburned fuel that it's trying to prevent, not a wasted spark. Unburned fuel ruins catalysts - wasted spark doesn't hurt a thing.

[Tank151]

Bmwdirtracer, I sent you a direct message

[bmwdirtracer]

What was the result of the smoke test?

[Tank151]

They’ve rescheduled me, I guess the guy who does the test was out sick from the shop. One thing I did do tho was unplug the maf sensor and take a small drive around the corner. It drove perfectly, no skipping or nothing. So it only skips in idle and shuts off with maf plugged in.

[328 Power 04]

I realize it's cold outside, do you have a moment to stick a flashlight under the hood at all the rubber tubing past the mass air flow and towards the intake manifold? Those crack and break easily with age, causing all the symptoms you describe.


Smoke test is gold standard, but taking a look isn't forbidden.

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Before doing any of that I would clean the MAF. Then I would swap coils and see if the misfire moves before replacing any coils assuming you still had this issue after cleaning the MAF.
Cyl misfire doesn't mean the coil pack is bad it means the ECU didn't let it that coil fire because he is reading bad data. Find the source of the bad data.

BMW has been using self-cleaning MAFs for the longest time ever. I don't think there is one case online where a BMW maf recovered after blasting it with some MAF cleaner.

[Tank151]

Do you think it’s possible that the wire that plug into the maf have a problem? It seems like it’s an issue to “click” in? Slides on and off pretty easy

[GriffX5]

BMW has been using self-cleaning MAFs for the longest time ever. I don't think there is one case online where a BMW maf recovered after blasting it with some MAF cleaner.

Is it not possible to exceed the limits of the self cleaning MAF? I have a cold air intake, not the standard airbox. I was told cold air intakes can sometimes leak oil onto the MAF. 3 times since I've owned it (purchased 10/05) I've cleared up running issues just by spraying CRC MAF cleaner on it. It's what appears to have cleared up my current issues.
I was getting misfires, random cylinders but Cyl 6 was pretty common. I swap coils, it drives fine for a while then misfires again, feels like motor mounts have failed. Sometimes it would try to stall when turning onto a side street. Swap coils and it repeats in a few miles. One guy here suggested unplugging the MAF, i see it acts like it does when the misfires occur so I decide to clean the MAF, again cold air intake issues, car is running like a beast, hates being under 85 on freeways like old times, i can take turns as low as 700 RPM in 3rd gear. If it wasnt the MAF cleaning clearing up the problem, what did I do?

If this is the case of the first time a BMW recovered after being blasted with MAF cleaner will I be famous? You want in on this?

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[MIKYZZ4]

Fine, as long as everyone is blasting it disconnected, and allowing it to fully dry,
before reconnecting and re-energizing at ignition.