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Go Back   E46Fanatics > Tuning & Tech > Driveline, Engine & DME Tuning

Driveline, Engine & DME Tuning
Talk about driveline improvements, NA tuning and DME tuning your E46 BMW here. This includes diffs, intakes, exhausts, chips, software and OBD tuning.

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Old 12-18-2016, 01:37 PM   #1
OldManHenry
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Join Date: May 2016
Location: Tucson, Az
Posts: 37
My Ride: 2000 stahlgrau 323it
intermittent m52tu misfire

Had to take the car out tonight and it was very obviously misfiring from the get go. this has happened sometimes on cold starts before and has gone away shortly thereafter (think 5-10 seconds) so I started driving. The misfire continued for the whole 5 minute drive. When I dropped off what I needed to, I turned around to go home (I didn't have to leave the car so I left it running). I decided to channel my PC troubleshooting and turn it off and on again. And it worked. What could cause a misfire to be tied to an ignition cycle? What problem could exist that off and on again would suspend the symptoms?


Recent work has been all new plugs and one new coil on the offending cylinder (always #4). Recent unrelated work being the cooling system refresh.
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Old 12-20-2016, 12:27 AM   #2
OldManHenry
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Join Date: May 2016
Location: Tucson, Az
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My Ride: 2000 stahlgrau 323it
Bump, it's still happening the same way. I shut off and start again almost immediately and no more misfire. Haven't had time to start poking around yet, trying to read up and see who has been in my shoes before.
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Old 01-17-2017, 02:37 AM   #3
OldManHenry
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Location: Tucson, Az
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My Ride: 2000 stahlgrau 323it
problem has gotten a bit worse, misfires heavier and longer... while the engine is misfiring there is almost a complete lack of power. You can floor it and the car might reach 10-15mph. When it finally turns over "clean" it runs great, no issues. It seems to be tied to a cold start. If I get it running right and go to a store, it'll start up fine when I'm done shopping. The issue only presents when the car has been off for an extended period of time.

I started pulling some things apart to figure it all out tonight, this is where I'm at so far (thankfully I don't need it as a daily, though it would certainly be nice to have):

fuel pressure is 45ish, I think this is pretty normal. Have a fuel filter on the way regardless, was thinking maybe it was clogged and was starving the engine of fuel at first.

I removed the upper and lower intake boots to check for obvious huge vacuum leaks, they're both in great shape. MAF looks clean and intact, though I don't know if I'd be able to recognize a problem visually with this part.

DISA valve holds vacuum on the flapper, looks to be in good shape. Doesn't hold the flapper completely closed when I plug the hole with my finger but I'm not sure if that's a realistic expectation. When the flapper does stop moving once the hole is plugged it doesn't budge... no slow leak. There is a fine layer of oil in the DISA area as well as the flapper, is this normal? Once I pulled it the oil smell was strong. New to engine work so I don't know if this should be an oil free zone or not.

I pulled the ICV but I need to read up on it before I know if anything is wrong with it and/or how to clean it.

I'm planning on buying a VANOS rebuild kit from i6motorworks as well as a valve cover gasket set to replace all that good stuff, following 50sKid's videos on youtube.

I've also seen some videos talking about a CCV delete and one referenced misfires but I'm pretty ignorant on that subject, have to read some more.

I pulled some codes but I'm in bed and they're down in the garage... I'll post them in later in case anyone is following this thread.

Last edited by OldManHenry; 01-17-2017 at 02:39 AM.
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Old 01-22-2017, 08:33 PM   #4
E36_Dinan3
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Join Date: Jan 2017
Location: New Jersey
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My Ride: E36 Dinan M3
Same problem with my girls e46. Runs great 99% of the time with an occasional misfire that will stay until you restart the car. Happens about every 20 cold starts or so. Not a big problem so far figuring a vacuum leak somewhere. SES light but no readable codes avail. Curious to see what happens with yours

Last edited by E36_Dinan3; 01-24-2017 at 10:35 AM.
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Old 01-22-2017, 08:37 PM   #5
E36_Dinan3
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Join Date: Jan 2017
Location: New Jersey
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My Ride: E36 Dinan M3
Also parts I've replaced:
-DISA Valve
-Intake Manifold Gaskets
-MAF
-Cleaned ICV
- All new Vacuum lines for PCV system
-New Vanos seals (vitton o rings)
-New battery
-Secondary air pump
-Spark plugs
- Swapped Could Around
-Crank sensor
- Intake and exhaust cam sensors

And probably more but problem still there

Last edited by E36_Dinan3; 01-22-2017 at 08:51 PM.
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Old 01-28-2017, 02:12 PM   #6
OldManHenry
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Location: Tucson, Az
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My Ride: 2000 stahlgrau 323it
great... I'm sourcing a DISA o-ring right now. I've got the green/black replaceable version but every local shop just wants to sell me a whole new valve, telling me my engine will blow up otherwise. Probably going to put the project on hold for a few weeks as I'm selling my house. I'll do the o-ring, reassemble and leave it until I can limp it to the next house (unless mine doesn't sell, of course).
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