90 Corvette Pinging Update

[WAYNE JOHNSON]

Some of the "Y" pipes I've seen are restricted at the weld joint, slide
the CAT off and look inside the "Y" pipe if it is ragged inside, it can
be corrected with a die grinder. I seriously doubt if this is causing
your problem though. Have you checked for a bad (lean) injector? If it is
on the opposite side from the 02 sensor, it could be causing the
problem.........hum I need to check for that on my car. Also have you
disconnected the knock sensor and listened for detonation?

On Tue, 20 Oct 1998 20:34:58 -0400 "The Thibodeaus"
<vettenuts at efortress.com> writes:
>Tonight I changed over to the stock chip.  At WOT, the stock chip 
>pulls out
>5 degrees of advance at 5000 RPM just like the Performance Resource 
>(PR)
>chip.  At highway cruise, the stock chip pulls out 1 degree of advance 
>under
>light acceleration, the PR chip pulls out 2 degrees.  At 20 mph where 
>the PR
>chip pulled out 15 degrees, the stock chip pulled out 3 degrees.  One
>blatant difference was the PR chip was indicating 0 duty time for EGR 
>and
>the stock chip was showing 99.4% duty time.  I have spoken with PR and 
>am
>returning the chip along with printed sheets of data from the PR chip 
>and
>stock chip for this 20 mph case.  They are going to send me another 
>chip as
>well as examine the data in the mean time.  So now I am left with the 
>fact
>that both chips are retarding my advance on the highway under light
>acceleration and at WOT.  Should I suppose this to be normal?  The 
>service
>manual indicates that the knock sensor is used to allow maximum 
>performance
>which could be interpreted as "they run the engine right on the edge 
>of
>detonation".  If so, a slight tip in of throttle may be too quick and 
>the
>knock sensor has to respond.  I have also read that the front Corvette 
>Y
>pipe has one pipe which crosses into the other internally where they 
>meet
>such that one side of the motor is more restricted than the other.  My
>thoughts right now are that maybe this is leaning out one side of the 
>motor
>and since there is only one oxygen sensor it does not detect this,
>especially if it is on the rich side.  Any comments on this or other 
>ideas
>what to look at are welcome.  I also appreciate the comments I 
>received from
>my original post.  Although I am using Sunoco Ultra 94 octane, I may 
>switch
>brands to see if this helps the situation.  Thanks for any input in 
>advance.
>
>Bob T
>
>

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