Re: teknickle difikulty

[Shannen Durphey <shannen@grolen.com>]

Somewhere around 1800-2200 rpm the module will advance timing if it's
not getting 5V from the ecm.  It's very sudden.  Disconnect 5V line,
start at 800, bring rpm up.  Watch for timing to jump.  

Timing matching with EST unplugged is a coincidence.  Prolly pretty
rare, too.  You might want to buy a lottery ticket since you're
beating the odds today.

With the EST disconnected  I'd bet it wouldn't take much to find an
rpm/vacuum where Diacom and the timing light don't agree, if you were
trying.

Shannen
Carl Summers wrote:
> 
> Hi All,
>      Working on a 94 Chev Pu here with Blower and TBI, 7427 4l60E....has
> been running well for about 4 years...Runs really poor now...I start with
> the basics and check timing and fuel pressure....fuel pressure is good but
> timing is 22degrees with est plug disconnected(should be 0)....so I attempt
> to move it back and it doesn't like it...dies every time....I notice on the
> diacom that the IAC counts down to 0 AND the diacom shows 22 degrees advance
> with the EST unplugged....hmmmm....unhook the IAC motor and hook up my IAC
> tester/driver and close the IAC completely and engine still idles at
> 800.....anyway bottom line on the iac stuff is I have a vacuum leak between
> the blower and the intake manifold...My question is: Have any of you seen a
> spot in the code that increases timing back to what is in the table if IAC
> will not lower the rpm enough???? Kinda seems backwards....I was thinking I
> had a bad ecm at first since I had an IAC code, EST code and some
> others....The timing with and without the EST wire plugged in always matches
> what the diacom says so seems as if all is well with the ECM....Oh well just
> checking with Y'all if you have seen this before....ttyl
> -Calr Summers
> 
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