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Author
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Topic: What causes knock?
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Five Decimal Zero
CAFords OG
Member # 1251
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posted
 
 
For some reason, my car was knocking pretty bad at low rpm when the weather was hot(90-100 degrees). What could be the cause of this? Knocking never happens during normal weather conditions.
Posts: 972 | From: San Jose, California | Registered: May 2002
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QwikStang
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Member # 2933
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posted
I was getting the same thing. A really loud pinging, especially going uphill. I was thinking that my timing was off.
anyone know why it does this?
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95 GT Vert
1 of 2,584
Where there is no patrol car, there is no speed limit.
http://www.cardomain.com/id/qwikstang
Posts: 573 | From: San Jose, CA | Registered: Jun 2003
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Primer GR40
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Member # 476
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posted
cheap gas or timing is off. also may need a tune-up
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Superdupercharged Cobra
No Transmatic Notch
Posts: 2108 | Registered: Sep 2001
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Five Decimal Zero
CAFords OG
Member # 1251
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posted
i heard and felt it going to the car show up that damn hill! could it be anything else that causes this?
Posts: 972 | From: San Jose, California | Registered: May 2002
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Sean90GT
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Member # 33
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posted
It's a combination of the heat we've been having, your timing setting and the grade of gas that you are using.
Your car is pinging, which is also known as detonation. Your car is running hotter than normal because of the weather. Lower grades of gas (87 octane) are more volatile and will ignite at lower temperatures. So, when you are running hotter your gas is pre-igniting and this causes the knock (which is BAD for your motor). Basically the air/gas mixture is combusting before the piston has reached the top of its compression stroke. The combustion is pushing down on the piston while the crank is still trying to push up on the piston. You noticed it on the hill because the motor was under a heavy load lugging up the hill.
In the hotter weather either back your timing off a couple of degrees or run one grade higher fuel. Some people also suggest running a little cooler thermostat but I'm not a fan of that.
Posts: 543 | From: Then: San Jose, CA Now: Phoenix, AZ | Registered: Jul 2000
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Five Decimal Zero
CAFords OG
Member # 1251
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posted
I only run 91 octane so i will bring the timing down a bit. Thanks!
Posts: 972 | From: San Jose, California | Registered: May 2002
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ci$ko
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Member # 2425
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posted
a bad ass exhaust leak...i got one right now..goin to rip it apart 2morrow when i get my new gaskets
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2000 GT for sale
89 lx burning up slicks at a track near you
91 bottled gt sold :/
72 chevelle
Posts: 1286 | From: valleJo .7o7. | Registered: Feb 2003
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Five Decimal Zero
CAFords OG
Member # 1251
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posted
i noticed that the inside of my car has been smelling bad lately... and i have tailpipes! shit, i guess i have to go through my whole car with a fine toothed comb.
Posts: 972 | From: San Jose, California | Registered: May 2002
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