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Basically Stock
2009 GS Turbo. 2007 Mid Engine GT
Joined
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7,512 Posts
Knock sensor: Not needed until it is, then it can save the engine

I've used seafoam in the engine oil a bunch of times. It's good for cars that have had oil changes too late and built up deposits. I put it in with the engine hot after a hard run, let it idle a while, then remove the cruddy oil. I also like the top end cleaner. I've seen the difference it makes when taking engines apart that have had it done vs not. A lot less carbon buildup on the valves and pistons
 

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Basically Stock
2009 GS Turbo. 2007 Mid Engine GT
Joined
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7,512 Posts
It wouldn't hurt matters.

And you won't get a CEL unless the knock sensor works. Lack of sensor gives the same signal as no knock--silence. It's basically a microphone on your engine. Vibrations make it move, and past a threshold its considered knock. That's why other things like a loose piece on the engine can also set them off
 

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Basically Stock
2009 GS Turbo. 2007 Mid Engine GT
Joined
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7,512 Posts
I can't see how. It's about engine protection

Plugged in:
When there's no signal from it, the engine thinks everything is ok, so it won't pull timing or add extra fuel

However when there is a signal from it, the engine has an issue, it will pull timing and add fuel.

Not plugged in:
There's never any signal, so it thinks the engine is healthy and there's no reason to go into a protective mode (even if it's knocking like crazy it won't protect itself)
 

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Basically Stock
2009 GS Turbo. 2007 Mid Engine GT
Joined
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7,512 Posts
It's audible if strong enough and you know which sound it is.


To make things VERY specific in how the sensor functions with the ECU software:

Using knock sensors, the car will decide if it's able to go higher on the ignition/fuel maps towards optimal setting of 100% learned octane value. 100% is the optimal spot the car should be at. Below that, the car isn't running optimally (but doesn't mean it's BROKEN, just not as good as it could be). Lower values indicate normal wear, poor/wrong fuel, or damage. That's why some guys run better on 93 octane, even though the GT only needed 91 when new. It's not an illusion every time, and there is a quantifiable way to check with an OBD scan tool (learned octane value) with live data display capabilities.

Octane learned value when high does optimal ignition timing and fuel use

When low, it pulls timing (less efficient, meaning you need more fuel and air to make equal power, including cruising) and generally richer ratios

Below 89c coolant temperature, it won't try to learn new values.
Learning happens ONLY in the 1500-3000rpm range.

To decide if it goes up or down, the car splits it into a high load and a low load mode.

Low load is below 160 load value (a complicated to compute value that looks at how much force the engine is putting out, basically, without being externally measured).
High load is 160+

At low load, if it detects 12.5%+ of max value sweep on the knock sensor for 0.6 seconds, it will lower the learned octane value. If it's below 12.5% for the 1.8 it will learn up the octane value.

At high load, if it sees 25%+ max sweep value it will trigger the learn down. Less than 25%, it can learn up. The engine naturally makes more noise and vibration under high load, which is why the value can't be 12.5%

Beyond 4000rpm, the car will look at knock enrichment. This is adding extra fuel beyond the typical values. I don't have that data on exact amounts of change in front of me.
 

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Basically Stock
2009 GS Turbo. 2007 Mid Engine GT
Joined
·
7,512 Posts
Wheel speed sensors throw their own code when they have an illogical response.

U1120 for a 4G eclipse is "Failure information on ECM or PCM". The cause is no output to the "ABS/TCL-ECU , Combination meter, A/C-ECU" from the ECU/PCM (manual vs auto, and combination meter is the instrument cluster on the dash). The diagnostic test step 1 is check the bus line connections and wiring for damage. Previous owner may have cut a bus line in the CAN. If all the wiring checks out, step 2 is to replace the faulty module.

Here's the section of the service manual on the CAN network

Page 87 in the chassis section better refers to troubleshooting
 
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