I thought my problem was with the increased timing advance from the Performance Resource chip -not so. I put the stock chip back in and the knock was slightly worse. The PR chip has the cooling fan on all of the time with the temp down to 196'. With the stock chip the temp was up to 220'+. I checked for loose brackets or anything else that would bang up against the engine at speed and found nothing.
The tank was almost empty of the 91 octane gas in it, so I went ahead and filled up with 93 to see if there would be any difference -there was none. I had put some combustion chamber cleaner in the tank last week.
I noticed that as the revs increased the amount of advance it was taking out decreased from 12' down to 4' or 5' just before shifting. I will soon be checking the fuel pressure to make sure its not going lean but, that wouldnt make sense with the knock decreasing at the upper end -would it?
Is there anything that would show up on the Tech 1 that I could look for that would help me figure out why this thing is still knocking?
The SES light is not on & there are no stored codes.


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89 IROC-Z 5.7L 2.77 GEARS
130,000 MILES
ALL FREE MODS
K&Ns FILTERS
FLOWMASTER MUFFLER
PERFORMANCE RESOURCE CHIP
AFPR & PORTED PLENUM
Best 1/4 E.T. 14.09 @ 97.2 MPH
Best 1/8 E.T. 9.09 @ 77.4 MPH
Best 60ft. 2.03

[This message has been edited by whiteroc (edited September 23, 2001).]

 

well, on the tech 1 you can check for your o2 readings. other than that check your base timing. is your air intake temperature sensor relocated? if it is you may want to relocate it. it may also be possible that someone put in a 5.0 liter knock sensor sometime in it's life and that also could cause a problem. if none of these help, just move your base 1 degree at a time until you see no knock at the temperature your thermostat is. a little spark knock at like 190 degrees is fine, but at like 160 to 170 you shouldn't have any.

 

If you're convinced that there is no REAL knock happening you can always bypass the knock sensor by putting a 3900 ohm resistor in place of the actual knock sensor on the side of the block. Not a bad diagnostic tool, either.

The knock sensor itself can be going bad (the piezo-electric mechanism gets flaky after many years) or it could simply be installed without correct thread prep and/or overtightened. Any of these can cause the sensor to be more sensitive than it should be.

 

Can you explain how to do this a little bit more? Where can you get the resister at? And which wire do you run it off of? I don't mean to sound like an idiot. I would like to learn more about this. I think my sensor is shot by the way my car has been running. I have a 305 (temporary) in a origionally equipped 350 Iroc. And I am using a 305 Knock sensor. (I thought they were the same)

 

How do you check the EGR Valve for correct operation. I remember something about bad EGRs or for that matter, removed EGRs(blocked off)that decrease the spark knock tolerance. Does anyone have more info on this subject? -Thanks for the help guys.