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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 02-22-2010, 11:25 PM   #1
frankymofe
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acceleration question

im curious if anyone here would have some advice or suggestions for me.
i have a 2000 323i.
when im driving the car hard, full throttle, ill notice that my power seems to "pulsate" at times..almost like its not very constant. its not extremely noticable but can be noticed enough. its not a fast pulsing of power, just slightly at around 2500-3000rpms and again around 4000...it seems like the power dips just a little then comes back. kind of odd.

has anyone else experienced this? i have no codes or anything. but after a while it has bothered me. im completely stumped.
any suggestions would be helpful. thank you.
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Old 02-23-2010, 12:20 AM   #2
Another BM
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could very well be your vanos at those rpms..
your power band pretty much kicks in at 3k.


I would first suggest getting your motor scanned.. If nothing turns up then replace you Vanos seals.

Search the forums for vanos seals and you will get plenty of info
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Old 02-23-2010, 12:29 AM   #3
frankymofe
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i have already replaced my vanos seals approx. 5000 miles ago. i never really noticed a difference after replacing them too..

since i had the car iver replaced my plugs, air filter, and fuel filter.
i plan on replacing a few other things..like my pre-cat O2 sensors, maybe my camshaft sensors...
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Old 02-23-2010, 12:48 AM   #4
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OP, you've definitely changed all the right things so far, if there are no codes to go on,
were all going to be guessing at this one. On the cheap side, I'd run a can of BG 44K
fuel injector cleaner through it, this stuff is worth its weight in gold/it works. Then maybe
you have a fuel pump starting to fail.

Good luck, i hope you figure it out.
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Nitrous is a little trickier than boost, but it's not the spray that kills motors, it's STUPIDITY!!
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Old 02-23-2010, 09:35 AM   #5
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OP, you've definitely changed all the right things so far, if there are no codes to go on,
were all going to be guessing at this one. On the cheap side, I'd run a can of BG 44K
fuel injector cleaner through it, this stuff is worth its weight in gold/it works. Then maybe
you have a fuel pump starting to fail.

Good luck, i hope you figure it out.
i'm 100% with rob.
sounds like you did a good tune up.

mmmm once again get it scanned at the dealer or an indy shop with a GT1 and hope it comes up with something.. i hope an error comes up and it will only cost you $50 to fix.
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Old 02-23-2010, 01:50 PM   #6
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yea haha thanks everyone. im not a "real mechanic" like at a dealership but i been workin on alot of cars in my life. i will definitely take it to the dealership n see what they can find cuz im stumped as well hehe. ill let you all know by the end of the week hopefully.

Last edited by frankymofe; 03-24-2010 at 08:34 PM.
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Old 02-23-2010, 04:41 PM   #7
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another quick question..
since i plan on repacing my pre-cat o2 sensors...should i also replace my post-cat ones as well?
curious if i need to or not, cuz these things arent cheap as we know haha.
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Old 02-23-2010, 06:28 PM   #8
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dont replace it if it isnt broken..
also only use the dealer for a scan.. get the work dont at a respected bmw indy shop in your area..
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Old 02-24-2010, 11:21 PM   #9
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well the o2 sensors im pretty sure need replacing, i can understand if the camshaft sensors arent broken dont replace them...but do they "wear out" like lose their continuity after alot of mileage?
i actually might try the seafoam challenge haha...but maybe ill just try the injector cleaner Rob43 talked about earlier..n see what happens.
i just ordered some pre-cat o2 sensors. maybe they will help..

any other suggestions??
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Old 02-24-2010, 11:43 PM   #10
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Have an intake? MAF issue?
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Old 02-24-2010, 11:53 PM   #11
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i do not have an intake, i do have a drop in K&N filter thats i check constantly to see if its still clean, which it is
i also cleaned the MAF, per directions, with a can of CRC MAF cleaner about the time i did my vanos seal replacements.
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Old 02-25-2010, 12:58 AM   #12
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Quote:
Originally Posted by frankymofe View Post
i also cleaned the MAF, per directions, with a can of CRC MAF cleaner.......
This could be a problem. I can't remember if the MAF fails like a light switch or if it degrades
over time, hopefully someone else will answer this. So I'm at the dealer 2 months ago getting
a DME re-flash, & i start talking with the shop foreman about the mods I've done. The MAF
subject comes up and i tell him i bought the CRC MAF cleaner, he then goes into a 5 minute
talk about how bad any MAF cleaner is for a BMW. He said the MAF is extremely sensitive
& usually can't handle that type of solvent.
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Quote:
Originally Posted by RacerX View Post
Nitrous is a little trickier than boost, but it's not the spray that kills motors, it's STUPIDITY!!
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Old 02-25-2010, 02:00 AM   #13
frankymofe
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hmm i can believe this statement.
on the other hand, if something as sensitive as the MAF...if it were at all damaged from the solvent, i believe my car would be showing it.
like i said at the beginning, its a barely noticable, almost like a hesitation, of power at those rpms...
and again, no SEL is being shown..

im taking it to the dealer this weekend to have a scan done..see if they find anything.
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Old 02-25-2010, 02:40 AM   #14
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Originally Posted by frankymofe View Post
hmm i can believe this statement.
on the other hand, if something as sensitive as the MAF...if it were at all damaged from the solvent, i believe my car would be showing it.
like i said at the beginning, its a barely noticable, almost like a hesitation, of power at those rpms...
and again, no SEL is being shown..

im taking it to the dealer this weekend to have a scan done..see if they find anything.
Yes, i hear you, It's probably not the problem. But that was exactly what i was told, i then gave my new CRC MAF cleaner to the
BMW shop that normally works on my car, & the owner said "we don't use that on BMW's either".
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Quote:
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Nitrous is a little trickier than boost, but it's not the spray that kills motors, it's STUPIDITY!!
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Old 02-25-2010, 09:57 AM   #15
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I had that problem too ironically it was a small vac leak. no one but you or a car crazy guy would know about it and they would prolly have to drive. i'm guessing your feeling that break up slight delay on rpms around 3.2k? no? let me know. it was bugging the shit outta me (same thing no codes) i let it go awhile and next codes that came up were the CPS both needed to be replaced i was an idiot and bought them off ebay for 60 bucks for the PAIR... needless to say i was at the dealer handing out 260 bucks for them a few days later replaced those all was fine. after the CPS change I sharked my car and i've had zero problems i was thinking it was my vanos seals too man. But after hearing you replaced yours not long ago i'm glad i didn't. i can almost bet it's not a 02 sensor you would be throwing lean codes on the bank the sensor was bad on. If you get bank 1 and 2 at the same time you can damn near guarantee it's not the 02 sensors i got 130k on mine and they are still "good" anyone this one haunted me for a month or two GL
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Old 02-25-2010, 11:20 AM   #16
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Quote:
Originally Posted by Rob43 View Post
This could be a problem. I can't remember if the MAF fails like a light switch or if it degrades
over time, hopefully someone else will answer this. So I'm at the dealer 2 months ago getting
a DME re-flash, & i start talking with the shop foreman about the mods I've done. The MAF
subject comes up and i tell him i bought the CRC MAF cleaner, he then goes into a 5 minute
talk about how bad any MAF cleaner is for a BMW. He said the MAF is extremely sensitive
& usually can't handle that type of solvent.
That is correct. From my experience, MAFs do degrade over time. The DME wont throw a MAF CEL until the MAF starts to give readings that are outside of its operating parameters, which Im not sure about the BMW MAF, but most MAFs work on about a 0-5V range (my Maxima MAF ran on a 0-4.5ish V range).

That's weird about BMW MAFs not liking cleaners to be used on them. I actually always cleaned mine (on my other cars, never done it on the Bimmer) with Brake Parts Cleaner. The only thing to keep in mind is to wait a good 15-20mins after the engine being on. Last thing you want to do to a HOTWIRE (which is what a MAF sensor is) is to spray a cold liquid on it. You also have to allow another 15min for the hotwire itself to get back to ambient temperature (again, last thing you want to do is give voltage to heat up a hotwire that is super cold from the cleaner on it). The solvent would evaporate on the hotwire itself and no good can come from that, it will blow it.

I've seen MAFs get ruined from drivers/ mechanics doing exactly what Im saying not to do in the paragraph above. But again, this has been my experience with MAFs of other makes. However, I PERSONALLY dont see why it would be any different on a BMW MAF; after all (to me) a hotwire, is a hotwire, is a hotwire (goes back to the idea that BMWs are these gems that justify ridiculous prices for parts and labor just because they are BMWs, in my opinion).
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Old 02-25-2010, 11:36 AM   #17
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Have you checked the rubber boot between the MAF and intake? If it's cracked, it could cause the symptoms you desribe. I replaced mine not too long ago just because of age, and found it to be cracked under the outer part of the elbow, where I could not see it.
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Old 02-25-2010, 02:02 PM   #18
frankymofe
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yea around 3000 rpms is roughly where its happening, and its just a very slight dip in power..then comes back, so to speak a lil after 4000 or so rpms..
hmm i havent actually checked any of my vacuum lines since ive had the car. i planned on replacing most of them in the future anyways because of the age but maybe i need to actually look into it now haha. ill also check the boot as well. see if there is any damage. since i do plan on getting a S/C in the future its best to take care of the the small stuff now, especially vacuum lines
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Old 02-27-2010, 02:04 PM   #19
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i still think it's your CPS (cam position sensors) i doubt it's the MAF when your having MAF issues you stall out a lot when you go around corners you stall etc. you seem to be getting air/fuel in. Again if you had a vac leak you'd get misfires and lean codes. my bet is the cps
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Old 02-28-2010, 05:14 PM   #20
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sounds like it might be. i actually just seafoamed the car....yea i know. but after driving it a bit, seems like it has gone away for the most part. still im gonna do the other things i mentioned for GP.. ill update ya when the parts come in and i go to the dealer..
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