valve tap and octane

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10-10-2002, 08:04 AM

tsefreeflow

I'm Chillin

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Join Date: Oct 2002

Location: Phoenix, AZ

Posts: 194

valve tap and octane

Ok, I am an idiot and did not realize that my 90 300zx needed high octane. I bought car in missouri and drove it back to kansas (about 6-7 hour drive) using regular unleaded. When I got back I realized that at certain rpm's (like 4000) the car had a tapping sound under stress and acceleration. I since put in an octane booster and the tapping is still there. Should it go away through the tank of gas and then refuel with premium gas and see if it stops? Should it stop shortly or might it take awhile to clear out all of the older low octane gas? Any help appreciated.

10-10-2002, 01:29 PM

stl300z

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Re: valve tap and octane

That tapping sound to hear is pinging or also know as knocking. The high compression is causing the fuel to ignite too early in the compression stroke. Now your case is one of the few where I would recommend octane booster since octane booster is terrible for cars emission controls. You should immidiately top off your tank with the highest grade octane gasoline you can find, under no circumstances run the car at full throttle or an rpm where the pinging occurs until you can fill your entire tank with pure premium gasoline. Only then will you know if any damage was caused. On the bright side I have never heard of anyone causing damage to their enigine by running a tank or two of 87 octane gas. Serious engine damage would have shown up immediatly.