I recently bought the wife a stock 96 Z28 vert off Ebay. When I got it, it ran God awful. I threw the normal stuff at it, Opti, plug wires, plugs, filter etc.

Now it's running good but has extreme spark knock. As I have yet to scan it I assume the knock sensor is dead, but I'm stumped as to the source of the knock. I put 89 octane in it because my 94 runs perfect on it with never a hint of knock and has never shown any retard when I've scanned it. I checked the fuel pressure and it reads 38lbs ish and rises to about 44lbs under load. So I'm fairly sure the fuel pump is not to blame. I don't know what else to check. If the MAF or MAP sensor was bad I'd get a code. SES light is off with no stored codes.

I know several of you have fought knock issues but couldn't find much with search. What should I look at?

Thanx
Re'

 

try a tank of 93 first

 

I am gonna try that but this is way more knock than that is gonna fix. I can hear light knock just reving it in neutral.

 

Interesting that you would put LL octane in the car just because your other car seems to like it. I guess it's worth a try, but I just assumed since it calls for higher octane that it would be a good idea to put the higher octane in first to see what you have before seeing what you can get away with. No flame, JMHO

 

Is in not preforming and rattling or just rattling?

 

It runs great. A little rought at idle, but smooth above that. I'm not sure what you mean by "preforming". It knocking or deiseling like crazy mainly in 4th gear under acceleration. I'm gonna scan it today to see if the PCM is picking it up. I probably have a bad knock sensor.

I put 89 in it because my 94 loves it and this is only the 1st tank of gas I've run through it. There is also a $.20 difference between 89 and 91. I'm gonna try the 91 when this tank is done.

Re'

 

If you have a bad knock sensor, it would set a code, and the PCM would use an internal calculation to set almost continuous knock retard, ranging to 12-15deg. If you can still hear knock, with the sensor working or not working, you have a serious problem.

Without scanning it, everyone is just guessing.