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Discussion Starter · #1 ·
Will u hear this noise at an idle ?
 

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My Caliber has some spark knock mostly at idle or when just accelerating from a stop. I have had the update done but still have the knock. DCX says they are aware the update does not solve it in all cases and are working on another update.
 

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Huff said:
DCX says they are aware the update does not solve it in all cases and are working on another update.
GOOD! I'm not relishing the thoughts of quarreling with the dealer peeps again about whether or not it's "normal".
 

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Discussion Starter · #4 ·
I don't mean to sound like a dumba-- but can someone help me and describe this spark knock noise. I hear something after the car has warmed up.
 

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dgksleeper said:
I don't mean to sound like a dumba-- but can someone help me and describe this spark knock noise. I hear something after the car has warmed up.
Spark knock is when the gas/air mixture in a cylinder ignites before the sparkplug does. Thats why its often called pre-ignition knock.

Often it sounds like the engine has marbles in it. In the case of my Caliber it very much sounds like a diesel engine at idle or when just starting to accelerate from a stop. If you've heard a diesel you'll recognize the issue in your Caliber if it exists.
 

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Huff said:
Spark knock is when the gas/air mixture in a cylinder ignites before the sparkplug does. Thats why its often called pre-ignition knock.

Often it sounds like the engine has marbles in it. In the case of my Caliber it very much sounds like a diesel engine at idle or when just starting to accelerate from a stop. If you've heard a diesel you'll recognize the issue in your Caliber if it exists.
If the gas/air mixture is igniting before the sparkplug, then would using a gasoline with a higher octane rating help? I was thinking that since a higher octane rating means a higher compression ratio before it ignites, it would prevent the self-ignition.
 

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Sleazy said:
If the gas/air mixture is igniting before the sparkplug, then would using a gasoline with a higher octane rating help? I was thinking that since a higher octane rating means a higher compression ratio before it ignites, it would prevent the self-ignition.
It's not a compression ratio thing for the octane. Higher octane fuel has a higher flash point, so it doesn't burn as easily and doesn't create as much heat when burned, which reduces spark knock. Spark knock is usually caused by the fuel igniting before the spark plug fires due to hot spots in the combustion chamber, not the amount of compression.
 

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Compression will often do it as well. try putting 87 octain into anything running at 11:1 or higher. Many people are familiar with the dieseling effect heard from a car after shutting it off when running much too low of an octain on too high of compression engine. It will keep running on a cylinder or 2 using just detonation alone to keep it going. As you know compression create heat and low octain fuel being more volitile than high octain has a lower flash point.
 

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Fingernipp said:
Compression will often do it as well. try putting 87 octain into anything running at 11:1 or higher. Many people are familiar with the dieseling effect heard from a car after shutting it off when running much too low of an octain on too high of compression engine. It will keep running on a cylinder or 2 using just detonation alone to keep it going. As you know compression create heat and low octain fuel being more volitile than high octain has a lower flash point.
But once again, it's from excess heat in the combustion chamber, and yeshigher compression creates more heat, but it's still the hot spots in the combustion chamber causing the pre-ignition. Compression creating heat is the whole concept behind deisel motors. Our motors are not high compression motors. They were designed to run on 87, so it could be anything from just low quality gas(not low octane) to small bumps or ridges in the combustion chamber that needed smoothed out,to just too much timing in the computer.
 

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Don't forget guys, there is a pretty in depth discussion about the subject here: http://www.caliberforums.com/forums/showthread.php?t=1376&page=2

I had the same issue, and did have the flash done. The spark knock is still there, especially more noticeable when it's hot out (the air is less dense). I got the same story from my dealer - DC is aware that the flash didn't fix the problem and they have a software update on the way to address the issue.

I was told this 2 and a half months ago. I called again yesterday and still no sign of the new update.

I believe Chrysler was aware that this was going to be a problem well in advance of the Caliber's release. Take a look at page 232 of your owner's manual ..."Light spark knock at low engine speeds is not harmful....However, continued heavy spark knock at high speeds can cause damage and immediate service is required."

To me that is like saying a gunshot wound that doesn't hit a vital organ can be ignored without treatment, but if you get hit in the chest or something - go to a doctor right away. I'm willing to bet that most people who are not auto-savvy are unaware of what spark knock even is or what it sounds like. I have never seen an owners manual for anything that even mentioned spark knock, let alone it being "not harmful".
 

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quadrajet said:
I have never seen an owners manual for anything that even mentioned spark knock, let alone it being "not harmful".
Actually, our 2003 Saturn manual pretty much says the same thing. My guess is that most newer cars have such high compression ratios, that the engines are always on the verge of ping. Says the same thing that occasional light is OK, but prolonged or heavy ping should be addressed.

What I find VERY strange is that no one has brought up the fact the the engine can ping at IDLE! Usually, an engine will heat up & ping due to higher ambeint temps or engine load. I've NEVER heard of an engine pinging at idle. To me, that is a major problem....pinging at ~1000 RPM & no load.

J
 
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