Knocking Problem in 1990 Corvette L-98

[mrvette]

I would block the EGR completely, like I did, and re-start the ECU...drop the
battery for ~3 min, and go from there....give it time to relearn...

GENE

The Thibodeaus wrote:
> 
> I have a 90 Vette with a ported plenum and Performance Resources chip with a
> few other minor modifications.  I am having a problem with pinging and have
> been monitoring the engine with an Auto X-Ray system.  The porting of the
> plenum involved removing the walls behind the throttle plates but in front
> of the EGR passages.  I think they may have been there to establish a low
> pressure area for introduction of EGR.  With them removed, I may have upset
> the pressure balance of the original design.  I have found my pinging
> problem to occur in two block cells, number 10 and 14.  Does anyone know
> what these cells are defined as?  Block 14 occurred
> tonight at fairly low speed (28 mph) and 28% throttle angle.  I don't have
> the data on block 10 but it occurred at around 55 mph with slight throttle.
> My block learn numbers are also kind of low for these two cells.  The rest
> of the cells that I have observed so far range from 120 to 132 so on average
> I am in the vicinity of the magic 128 value.  Does anyone know if these
> cells are controlled by programming in the chip.  I am suspicious that the
> new Performance Resources chip I installed is the cause of this problem as
> they advertise "modified partial throttle" enhancements.  Also, I do not get
> any retard at WOT until about 4000 RPM after which the amount of retard
> grows to about 5 degrees at 5000 RPM.  Is this normal or is this another
> chip problem?
> 
> Bob T

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