E46 M3 unexplained misfire

[sihlem]

Hey guys

So I have encountered a problem with my E46 M3 where it misfired once and never again but I can feel that when idling that there's a weird drop every 5-7 seconds. When driving, as soon as I get to the 3rd gear at around 3000 rpm it struggles climbing.

Also, something new is that when looking to start the car, it needs to be cranked up 2-4 times before it actually switches on.

I've taken it to BMW but the problem still persists and at this point I think I'm the only one who notices these things. A sort of "I know how my car should be operating".

I've had the injectors cleaned, actuator replaced, ignition harness changed as well.

Need some help in determining where the problem might be.

Feedback would be highly appreciated because right now I am really confused.

Thanks guys.

 

[KPM3_30]

I suggest you contact @Peter@AEW if you are based in Jhb.

 

[Kish2604]

So lets start with some info first, model, mileage, service history etc... Then have you pulled codes to see if any faults has been logged? from there with misfires i would start with the usual culprits being plugs, coils, faulty MAF, blocked fuel filter/low fuel pressure issues and revert with feedback and your location as well....

Enjoy your stay on the forum...

 

[Spiro]

to be honest this sounds like an intake camshaft sensor issue, how is consumption and other bits going ?

 

[TurboLlew]

The solution in my case on the M5 was coilpack and fresh plugs. People other than me thought the idle was fine (including BMW) and it is difficult for ANYONE to judge an issue when an issue means the car might be making 420kw instead of 450 for instance... or that you have noticed the sound/manner in which it revs up has changed. Anyway I saw that momentary drop and change in tone that you are mentioning. I am sure it might be a different diagnosis on an NA car than I experienced but just sharing since you didn't mention having changed the coil packs and plugs. The offending coil pack looked fine visually by the way and did actually fire albeit unreliably.

 

[Crash_Nemesis]

I would venture to say this may be your Coilpacks... I literally had this issue and fixed it with new coils and plugs.

Also check your oil separator, this can get clogged and causes issues with positive crank ventilation and idle.

 

[E-Male]

Start by checking the spark plugs first bud, worn plugs often result in that 'fish-bite' effect on idle.

 

[VinceM]

Plugs and Coil packs


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[DJGyron]

Hey guys

So I have encountered a problem with my E46 M3 where it misfired once and never again but I can feel that when idling that there's a weird drop every 5-7 seconds. When driving, as soon as I get to the 3rd gear at around 3000 rpm it struggles climbing.

Also, something new is that when looking to start the car, it needs to be cranked up 2-4 times before it actually switches on.

I've taken it to BMW but the problem still persists and at this point I think I'm the only one who notices these things. A sort of "I know how my car should be operating".

I've had the injectors cleaned, actuator replaced, ignition harness changed as well.

Need some help in determining where the problem might be.

Feedback would be highly appreciated because right now I am really confused.

Thanks guys.

It could be a number of different things. It could be a air intake leak, MAF problem, Ignition coils, Spark Plugs, Fuel Pump, inadequate fuel pressure, Vanos solenoids clogged or a problem with the O2 sensors. Check your fuses as well in the cubby. What you need to do is a diagnostic inspection to see what fault codes you receive.

 

[QikNish]

Coilpacks and plugs should be looked at from experience.

 

[Clint@MMS AUTO]

Did you come right? i would have started with plugs and coils first as well.

Today I fitted new OEM NGK plugs in my S54 because the BOSCH ones i got from goldwagon Last year (1200km's ago) cause my car to have a rough idle.

 

[DJGyron]

Did you come right? i would have started with plugs and coils first as well.

Today I fitted new OEM NGK plugs in my S54 because the BOSCH ones i got from goldwagon Last year (1200km's ago) cause my car to have a rough idle.

I agree 100%, start there first.

Also, pull out all 6 spark plugs in the order of the cylinders. If you notice that the first three or last three have more carbon soot on them, it means that either bank 1 or bank 2 is over fuelling and that one of the O2 sensors on either bank is cooked. Then again a diagnostic with fuel trim readouts will give you a more accurate determination on the O2 sensors, especially figuring out if its pre-cat or post-cat.