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From: rls@ihu1g.UUCP (r.l. schieve)
Newsgroups: net.auto
Subject: Re: backfiring
Message-ID: <681@ihu1g.UUCP>
Date: Thu, 22-Aug-85 09:08:18 EDT
Article-I.D.: ihu1g.681
Posted: Thu Aug 22 09:08:18 1985
Date-Received: Sat, 24-Aug-85 15:28:56 EDT
References: <908@mtuxo.UUCP>
Organization: AT&T Bell Laboratories
Lines: 63

> I have a Mercury Capri with a carburated 2.3 liter engine.
> I am experiencing backfiring when ever I let off the gas.
> Would anyone out there know what causes this and how I can fix
> this? Thanks.
> 
>                         George Valentini
>                         mtuxo!gv
>                         (201) 576-6198

I unfortunately have had a lot of experience with the 2.3 liter
engine as I had one in the Mustang I sold this year.  There are
other causes for backfiring but the one that I would suspect most
from the 2.3 liter 4 banger is timimg problems and you may have to
go further than just checking the timing with a timing light to
be sure.

Your engine has a timing belt under a cover in the front that
connects 3 points.  The driving point is the crankshaft at the
bottom.  The things that it drives make this engine somewhat
different.  As with most engines the crankshaft drives the camshaft
(overhead cam in this case).  But on most engines the camshaft
drives the distributor and oil pump.  On the 2.3 liter engine the
distributor and oil pump are driven by an auxiliary shaft which
is the third point the timing belt contacts.  (gosh my big chance
to draw a picture!!!!)  
              _
             /O\ < Cam
             |  \
             |   \
     Crank > \O__O| < Auxiliary

           Front View     

There is also a tensioner under the belt by the camshaft to help
hold the belt tight only during initial installation.  It is
held in place by a locking bolt so it cannot take out the slack
that eventually developes.

A timing light will tell you if the crank and auxiliary shafts
are in sync but will tell you nothing about the cam shaft.  The
timing belt is notched on the inside but as it wears and gets
loose it can easily slip a notch.  The only way to be sure every-
thing is in sync is to go through the alignment procedure.  There
are marks on the crank and cam visable from the front with the
timing belt cover off and the auxilary shaft id positioned so
the distributor is pointing at cylinder one when the crank and
cam are lined up.

The problem is probably due to an old timing belt that has slipped
and needs to be replaced.  My engine had a turbo which incorporated
a high volume oil pump.  The auxiliary shaft drives the distributor
and oil pump by the gear at the back of the auxiliary shaft driving
a ring gear held in place on the distributor shaft by a roll pin.
The added drive needed by the oil pump at high RPMs sheared the
roll pin.  The ring gear would slip a little and the car would die.
I would readjust the timing and the gear would hold in place until
the next time I really pushed it.  I played around with the timing
belt 3 times before I thought to check the roll pin *&%$#@@!!

			Good Luck

				Rick Schieve
				....ihnp4!ihu1g!rls