5.7 TBI Questions

[Bruce Plecan]

> > Situation: 5.7L w/700R4 trans, from 89 Chev pickup swapped into 84 G20
van
> > (305 removed), ECM #1227747, cal-pack ANLW.
> > Installed with freshly built long block from a not-so good rebuilder
(too
> > late smart)
> > 1. Engine went bad (exhaust valve stems mushroomed, broken lifter) after
> > 30K miles. What would cause an observed excessive carbon build up on the
> > stem side of all the intake valves?

Cheap additive package in the fuel used, Engine blow-by with oil entering
the intake tract.

> > 2. Does the presence or absence of catalytic converter(s) affect the
> > proper function of the O2 sensor?

Not enough to worry about with a 747.

> > 3. The G20 van has a lower ratio (3.08:1) differential than the pickup
> > (3.42:1).  Any suggested changes to efi and/or ecm that I should be
> > looking into to get this combination to run better.

747 is a rather "dumb" ecm.  *might* take a little timing out faster going
from 40 toward 100 K/Pa (but leaving the 100 entries alone).  Then use less
PE timing.

> > 4. (This one should probably be on the ECM list) ECM is intermittently
> > setting code 34. I have installed a vacuum gauge and test light to
monitor
> > when the ECM is 'testing' the EGR valve. What I'm seeing is low vacuum
at
> > the throttle body port where the EGR vacuum is tapped off going to the
> > controlling solenoid valve. Obviously, the wider open the throttle, the
> > lower the vacuum. So, if the ECM 'tests' the EGR at a high steady speed,
> > the low vacuum isn't enough to have the EGR valve open. Therefore when
the
> > ECM signals EGR valve to close, being closed already, there is no change
> > in
> > the O2 reading and the ECM assumes a bad EGR and sets code 32. If the
test
> > happens at a low, steady speed (I seem to recall 40MPH as a minimum),
then
> > there is enough vacuum to have the EGR valve open, so it actually
closes,
> > satisfying the ECM's test. What suggestions are out there to fix this
> > problem?

Look for a different base calibration.  Or better yet try a bunch. the EGR
was / is a bug a boo on some applications, jus cause...
>

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