164 24-valve timing belt report

["Colin Verrilli" <verrilli@domain.elided>]

My '94 LS is back on the road after a timing belt change (done by me) so
I'd thought I'd report on a few
findings...

The original problem was a missing at idle...very obvious from the
exhaust. I started off on
the wrong path when I read a 1255 error code from the Motronic which
called out the cam sensor.
I went further down that path when I followed the diagnostic procedure
in the manual which said
that the resistance across the sensor should be 20 (I think) ohms. Mine
read 550. Turns out the manual
is wrong. 500 ohms is ok. Luckily, I found this out before ordering a
new one.

I then dug into the timing belt. The shop manual and associated service
bulletins are a requirement
for this job. It's a very involved procedure which includes removing the
intake system, ignition
coils, cam covers, cam caps, lowering the left side of the engine and
removing several pulleys
from the engine block. Special alfa tools are also required to lock the
cams in place and to adjust
the tension on the belt.

Marked cam sprockets help with this procedure. If the car already had a
timing belt change performed
by a dealer (mine had), it probably has the cam sprockets marked (with
white paint). The marks on the
cams allow you to quickly tell if the cams are timed properly (in
relation to each other). This
is a rough indication, but enough to tell you if it's off by a tooth.

I found that one cam had slipped one tooth and that the belt was loose.
At first I thought that the
tensioner was the problem because it wouldn't retract. Later, I found
out that the tensioner will
only retract if given constant pressure for a long period of time (like
5 minutes).

So it's all back together now with a new belt and new tensioner. Not
sure what caused the belt to
slip (and stretch?). It did have 40K miles on it. Maybe I just waited
too long.
I had been planning to change it over xmas break.
I plan to check the tension in a few thousand miles. Should be a piece
of cake now...

Colin Verrilli

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