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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Powertrain and Drivetrain Discussions > N54 Turbo Engine / Drivetrain / Exhaust Modifications - 335i > 87 Octane Accident



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      05-09-2012, 05:31 PM   #1
dnadeau13
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87 Octane Accident

I normally only use 93 octane fuel but my car started rather rough the other day. It settled down after a minute or two. It felt like it was dieseling or knocking. I think I may have absent mindedly filled up with 87 octane.

I then filled up with half a tank of 93 octane. I am now back down to 3/4 of a tank. Today it started more rough then before and the check engine light came on.

Can low octane fuel really throw a code? Or should I be looking elsewhere for the problem?

After running through a full tank of 93, is there anything I should do/check/clean?
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      05-09-2012, 05:39 PM   #2
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i don't know if you should really check anything, but i know the DME will just pull timing to compensate for the low octane. just dont floor it until you're out of the bad gas and you should be fine.

scan the car if you can to see what codes popped up.
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      05-09-2012, 05:39 PM   #3
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Just got it read at AutoZone and it threw codes P0301 and P0303. Which is a misfire on cylinders 1 and 3.
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      05-09-2012, 05:39 PM   #4
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if there were no problems before you filled up, i'd toss in some fuel injection cleaner/octane booster with your next tank and hopefully that'll cancel out the crap you accidently put in your tank
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      05-09-2012, 06:38 PM   #5
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Quote:
Originally Posted by benzy89 View Post
if there were no problems before you filled up, i'd toss in some fuel injection cleaner/octane booster with your next tank and hopefully that'll cancel out the crap you accidently put in your tank
Octane booster won't cut it. OB's only raises octane by fractionally (i.e. it takes a 10 point octane booster to raise the octane by 1 (10/10ths).

I'm with Javier, just don't go racing around everywhere. The DME will retard your timing, affect performance, but won't hurt the motor unless you do something stupid.
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      05-09-2012, 07:02 PM   #6
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you can buy 60 point (and 90 point) octane booster in napa/autozone, but i'm also in agreement that you hold off on the "spirited" driving until all the crap out of your tank
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      05-09-2012, 07:32 PM   #7
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I'm having the same misfire symptoms on a cold start, it could not be the gas at all, maybe just a faulty injector.
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      05-09-2012, 07:43 PM   #8
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Throw in a couple of gallons of e85 to raise the octane.
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      05-09-2012, 08:09 PM   #9
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Quote:
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Throw in a couple of gallons of e85 to raise the octane.
lol e85 the cure to everything. I'm running it on my n55 right now too haha.
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      05-11-2012, 11:53 AM   #10
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It progressively got worse to the point of almost stalling after a cold start and not firing on all cylinders for at least 10 minutes after starting. Brought it in because I didn't feel comfortable waiting until I could take a look at it. Three fuel injectors need to be replaced! Starting to think that I didn't actually put 87 octane in it.
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      05-11-2012, 02:42 PM   #11
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Quote:
Originally Posted by phazen23 View Post
Octane booster won't cut it. OB's only raises octane by fractionally (i.e. it takes a 10 point octane booster to raise the octane by 1 (10/10ths).

I'm with Javier, just don't go racing around everywhere. The DME will retard your timing, affect performance, but won't hurt the motor unless you do something stupid.

I would also pull the plugs and check/replace them.
Some techron inj cleaner should also be thrown in a couple times a year.
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