e36 Knock and ping question

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Erik - 02 Feb 2005 19:23 GMT

1993 BMW 325i Automatic Transmission

I am using 91 Octane gas (Best I can find in Southern CA) and am getting
knocking and pinging when the car shifts into the next gear or under load.
It seems to go away with higher revs, but where I live higher revs are not
an option always. I have used fuel cleaner and good quality gas (to the best
of my knowledge - Chevron and Shell). I know the computer compensates for
gas octane rating, so I am puzzled. Any thoughts?

Thanks,

EJ

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Raybender - 03 Feb 2005 01:48 GMT

> 1993 BMW 325i Automatic Transmission
>
[quoted text clipped - 8 lines]
>
> EJ

According to the instructions with my Peake Code reader, some '93 325's have
knock sensors and some don't. If the 5th digit of your VIN number is an 'F'
then your engine should have knock sensors. If it is a 'B' then you don't.

Assuming you're one of the lucky ones with knock sensors, then it appears that
the first thing to do is get them checked out - must have failed. If you don't
have knock sensors, then you need a thorough check to see if you might be
running lean, because of an air leak, poor O2 sensors, low fuel pressure, or if
your engine is carboned up. Compression test would tell you if you're carboned
up.

Best luck

Frank

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