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Discussion Starter #1
The engine on my '94 G20 started pinging/knocking a month ago. I decided to fill up with 94 octane, and voila, no more noise. The car has 107,000 miles on it and has been well maintained.

I'd like to continue using regular gas, but because of the knocking I really don't want to.

The engine is stock except for a JWT POP.

Any suggestions before I pay an expensive visit to Infiniti?
 

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Check your timing....and check spark plugs....use the guide on NGK site to compare your spark plugs....spark plugs pretty much show what problem you are having...
 

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If it still pings/knocks after you done the basics, it's probably due to the carbon build-up in your engine which causes the temperature in the combustion chamber to run hotter. That's why when switching to higher octane gas, the noise stops.

The octane quality of a gasoline is its ability to resist detonation, a form of abnormal combustion. Detonation occurs when the air-fuel mixture reaches a temperature and/or pressure at which it can no longer keep from self igniting. Two types of abnormal combustion are common: the first is detonation as previously mentioned and the other is preignition.

Detonation occurs after the spark plug has ignited the air-fuel mixture and the flame front is moving smoothly across the combustion chamber. If, during this burning process, the unburned air-fuel mixture reaches a temperature and/or pressure at which it is no longer stable, it burns very rapidly causing a new flame front to collide with the one that originated at the spark plug. Maximum pressure in the cylinder occurs before the piston reaches top dead center (TDC) and that pressure try's to push the piston down before it is ready to go down. Piston burning and rod bearing damage are the result.

Preignition is the other bad actor and is usually started by a hot spot in the combustion chamber which causes the mixture to ignite before the plug fires. Under wide open throttle conditions, preignition will destroy pistons in seconds.

Bring your car to a good mechanic who can remove the carbon build-up in your engine.
 

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best i can say is its like marbles rolling around under your valve cover ...
 

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Discussion Starter #7
This is strange, I used 1 tank of 94, then a tank of 89, then back to 87 and the noise is gone.

I had my thermostat replaced which was broken (stuck in the open position) but I don't think that would have anything to do with it.
 

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maybe changeing octaines got rid of some of the carbon ?

happens after running injector cleaner thru some cars too, goes away for months then comes back was a real problem with 2 liter cavaliers ...
 

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it also might be the timing chain tensioner... ive heard that thing wears out really fast in the sr20

if you guys want to hear something really cool.... grab a 2x4 and put one end on the valve cover and the other end against your ear.... (you can hear in the engine) sounds pretty cool

this could also help if the noise comes back. it will help you decide if its the timing chain, the valves or what not
 

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NISMO1028 said:
it also might be the timing chain tensioner... ive heard that thing wears out really fast in the sr20
I do not believe that it actually 'wears out'. Nissan has come out with 4 different versions of the tensioner over the years due to start-up clatter.

The only known issues with the earlier tensioners is start-up clatter, not a constant pinging or knocking noise. The start-up clatter only lasts for a few seconds and does not cause any issues with the SR20's lifespan.
 

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NISMO1028 said:

if you guys want to hear something really cool.... grab a 2x4 and put one end on the valve cover and the other end against your ear.... (you can hear in the engine) sounds pretty cool



LOL
 

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why is that so funny?
 
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