5.7 TBI Questions

[Don.F.Broadus at ucm.com]

1. excessive valve guide clearance is common in 5.0  5.7 L  heads oil builds
up on valves

> -----Original Message-----
> From:	K.E. Towle [SMTP:karljiml at compuserve.com]
> Sent:	Friday, July 07, 2000 12:32 AM
> To:	INTERNET:diy_efi at diy-efi.org
> Subject:	5.7 TBI Questions
> 
> Any answers to the following questions would be appreciated:
> 
> 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?
> 
> 2. Does the presence or absence of catalytic converter(s) affect the
> proper
> function of the O2 sensor?
> 
> 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.
> 
> 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?
> 
> Thanks,
> Karl
> --------------------------------------------------------------------------
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