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      11-12-2012, 10:53 AM   #56
pbar
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Drives: 2015 M4
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Quote:
Originally Posted by m3an View Post
thanks for all the replies; I def know what knocking sounds like, and it's def a light ping under initial tip in of throttle but only if the car is kinda being lugged around (low rpm, higher gear). The performance doesn't seem off at all, and I mention fuel as a possible culprit as others have also before. I def don't think it's fuel related, moreso igntion; possibly timing. But this car now has the crazy knock detection system on the spark plugs so that's why I think it could poss be timing related. That being said, yes these cars are very noisy. My e46 sounded like a sewing machine, but always ran great. I suspect all M cars make noise, and maybe my ears are more sensitive that others (i have build and blown up many cars, lol) but this noise almost def sounds out of the ordinary compared to the typical M sewing machine/chainsaw rasp
I know exactly what you're talking about and this has been bugging me for two years now ever since I bought my first US M3. I've previously had several E92s and an E46 in Europe and never had this sort of issue before.

At first I put it down to running on 91 octane fuel (in California). However, my dealer has looked into this twice and not found an issue.

The symptoms are as you describe - if you are in a lowish gear, around 3K rpm and suddenly put in a reasonable amount of extra throttle you get a couple of seconds of metallic pinging / ratchet sort of noise before the car really starts to pick up. This happens more often on an uphill slope.

I realize the car is intended to be driven above 4Krpm most of the time, and the correct answer is to downshift - but this seems really soggy for such an expensive car. I haven't had to worry about this sort of thing since I drove a 650cc Fiat 126 in my teenage years!

I recently got an ESS tune, tailored to 91 octane to see if it improved the situation, but it made no difference. Perhaps I should have gone to Mike Benvo?

I was wondering if the noise might be something to do with the VANOS unit suddenly having to make a large timing adjustment? Is this even plausible? If it was knocking/pinging, would this be something that would be logged and you could read out from the ECU ?

I run my M3 almost exclusively on V-Power (as I did back in the UK) - and am quite worried by the comments in this thread about fuel quality. I guess I will try using Chevron or 76 for a while and see if it improves the situation.

If anybody else has managed to cure this issue I'd love to know.

Paul

Last edited by pbar; 11-12-2012 at 11:07 AM.
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