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Old 11-19-2010, 01:49 PM   #1
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Knock Sensor Question....

Hello everyone.....

I've posted in another thread or two about engine knocking that I've been having since the summer.

I have a '10 Sahara.

When I brought my Jeep in for its most recent oil change, about a month ago, I asked that they check it out to see if they can figure out what's going on.
I'm not sure if they needed to drive the Jeep to hear the knocking, but the mileage was the same when I got it back as when I dropped it off, so I'm convinced they didn't even check it out.
The service guy told me to put higher octane fuel in.
Earlier this week I called the service dept. back because I wanted to have them really look at it, again, the guy tells me that it's a common problem and Chrysler sent a bulletin...then he changed his words....'is saying' to put higher octane fuel in.
So I ask if one tank will fix the issue or will it require multiple tanks....he's not sure.
Great....I should have asked for him to give me that in writing and see what he said then.


I've been doing as much research on the issue as I can via Google, and a little on here.
As most of you on here know, the knocking can be happening for a number of reasons.
I found something online about testing the knock sensor:

^ Defective Knock Sensor: The knock sensor responds to frequency vibrations produced by detonation (typically 6 - 8 kHz), and signals the computer to momentarily retard ignition timing until detonation stops. A knock sensor can usually be tested by rapping a wrench on the manifold near the sensor (never hit the sensor itself). If there is no timing retard, the sensor may be defective.

OK, that's something I can do myself, BUT.....one thing I havent been able to find yet is where the knock sensor is located (I'd just like to know where it is) and does 'no timing retard' mean that when I hit the manifold while the Jeep is idle I should hear knocking?? If I don't hear knocking then the sensor is defective, correct?

Or could it really be a fuel issue?

SORRY for the long post, I just wanted to make sure I provided as much info as I could!!

Thanks in advance!!!

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Old 11-20-2010, 03:02 PM   #2
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Just in case anyone else may be having ping/knock issues, more searching took me here:

Where is '10 JK knock sensor located?

and here:

Still pinging! Why?

Maybe a change in gas is what I need to do and the problem is just unavoidable....bummer

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Old 11-20-2010, 04:25 PM   #3
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I have no idea where the knock sensor would be located but the way I interpret the instructions you posted is that when you tap the manifold the ignition timing should temporarily slow down slightly. Therefore, if there is no timing response when the manifold is tapped then the sensor would be faulty. Don't really know anything about the issue just paraphrasing the instructions.

Good luck
John

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Old 11-21-2010, 11:26 AM   #4
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Yea that makes sense. Thanks!
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Old 11-22-2010, 10:12 AM   #5
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Take it to a different service facility or insist this one remedy the problem. Speak to the Service Manager and make it clear that you want the problem repaired, period. If he/she is unable to do this, contact Regional Management and request a meeting to resolve the problem.

Document all attempts to repair the problem. If it cannot be fixed, you are entitled a refund of the purchase price under Lemon Laws. You don't have to put up with this kind of nonsense. And no, switching to higher octane fuel does not remedy this problem.
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Old 11-22-2010, 10:33 AM   #6
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my 2010 starting knocking a bit under heavy loads when they started filling with the winter blend gas, so i stepped it up to 93. knock is now gone.

but as stated above, it's supposed to run on 87 without knocks. my knocking has been pretty situational though, so i'm not ready to take it to the dealer just yet. the stuff that they try to pass off as gasoline is getting worse and worse every passing year, so it may be more on the gasoline than the knock sensor.
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Old 11-22-2010, 12:21 PM   #7
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Arrow

Quote:
Originally Posted by wrangler0 View Post
Hello everyone.....

I've posted in another thread or two about engine knocking that I've been having since the summer.

I have a '10 Sahara.

When I brought my Jeep in for its most recent oil change, about a month ago, I asked that they check it out to see if they can figure out what's going on.
I'm not sure if they needed to drive the Jeep to hear the knocking, but the mileage was the same when I got it back as when I dropped it off, so I'm convinced they didn't even check it out.
The service guy told me to put higher octane fuel in.
Earlier this week I called the service dept. back because I wanted to have them really look at it, again, the guy tells me that it's a common problem and Chrysler sent a bulletin...then he changed his words....'is saying' to put higher octane fuel in.
So I ask if one tank will fix the issue or will it require multiple tanks....he's not sure.
Great....I should have asked for him to give me that in writing and see what he said then.


I've been doing as much research on the issue as I can via Google, and a little on here.
As most of you on here know, the knocking can be happening for a number of reasons.
I found something online about testing the knock sensor:

^ Defective Knock Sensor: The knock sensor responds to frequency vibrations produced by detonation (typically 6 - 8 kHz), and signals the computer to momentarily retard ignition timing until detonation stops. A knock sensor can usually be tested by rapping a wrench on the manifold near the sensor (never hit the sensor itself). If there is no timing retard, the sensor may be defective.

OK, that's something I can do myself, BUT.....one thing I havent been able to find yet is where the knock sensor is located (I'd just like to know where it is) and does 'no timing retard' mean that when I hit the manifold while the Jeep is idle I should hear knocking?? If I don't hear knocking then the sensor is defective, correct?

Or could it really be a fuel issue?

SORRY for the long post, I just wanted to make sure I provided as much info as I could!!

Thanks in advance!!!
Sinister brought up a good point....... Just curious, what brand of gas are you using? I am sure all the brands are playing dirty tricks to save $$$$, but some brands are still better than others.
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Old 11-22-2010, 12:22 PM   #8
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Quote:
Originally Posted by JD Adams View Post
Take it to a different service facility or insist this one remedy the problem. Speak to the Service Manager and make it clear that you want the problem repaired, period. If he/she is unable to do this, contact Regional Management and request a meeting to resolve the problem.

Document all attempts to repair the problem. If it cannot be fixed, you are entitled a refund of the purchase price under Lemon Laws. You don't have to put up with this kind of nonsense. And no, switching to higher octane fuel does not remedy this problem.
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Old 11-22-2010, 02:37 PM   #9
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Quote:
Originally Posted by SLIM_SNOOPY View Post
Sinister brought up a good point....... Just curious, what brand of gas are you using? I am sure all the brands are playing dirty tricks to save $$$$, but some brands are still better than others.
95% of the time I use either Gulf or Sunoco as they are closest to where I live, most times I use Gulf as they are about .10 cheaper.
I've never had any issues with them and Ive been going there for years.
I should also mention that the knocking only started back in August, about 5 months after I purchased my Jeep, after I put gas in from another brand, not sure which one. I figured after a fill up or two from my usual brands, it would go away....it hasn't.
It's a subtle knock most of the time but other times, on rare occasions, it's louder and more frequent.

Quote:
Originally Posted by JD Adams View Post
Take it to a different service facility or insist this one remedy the problem. Speak to the Service Manager and make it clear that you want the problem repaired, period. If he/she is unable to do this, contact Regional Management and request a meeting to resolve the problem.

Document all attempts to repair the problem. If it cannot be fixed, you are entitled a refund of the purchase price under Lemon Laws. You don't have to put up with this kind of nonsense. And no, switching to higher octane fuel does not remedy this problem.
Yea, I agree on all of the above!
The problem isn't horrible...yet....but it's frustrating and even just thinking about dealing with the service people is tiresome at this point, after getting the run around twice....but it has to be done and I will call the service manager right after I'm done typing this!!

Thanks guys!
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Old 04-18-2015, 09:05 PM   #10
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Can anyone tell me how to check to make sure the sensor is functioning within specs?

Was looking for info on anti knock valve thread and saw this thread. Have an 03 TJ and was buy gas from the cardlock from the company I hauled fuel for. Serious knocking up the grade to home began to be a problem. Switch to top tier (Conoco Phillips 66-76) Premium grade. It took 2 years to drive off the build up but for the last 10yrs not a single ping.

It matters a great deal what quality and grade of fuel you use. If you plan on owning your jeep as long as I have its work the extra 5% you pay at the pump.

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