Still pinging! Why?
JK Freak
Joined: Jul 2009
Posts: 590
Likes: 1
From: State College, PA
Btw all, it got a little colder around here-30s in am to 40/50 in pm, & I switched to 89 gas. Drove a bit and added 6 gal of 93 to tank (station was out of 89) and no pinging / ignition knock! If this thing needs 93 that's going to be $$$. Bummer. Seems like easy fix, tho, if the gas was the cause. fWIW.
I figure if you put in a small amount of 87 from another station to test whether it is the outside air temps or not, it can't hurt. If you start to hear it knocking again just fill the tank the rest of the way with 93 and you will end up with a final blend high enough knock resistance to make it to your next fill-up. If it doesn't start to knock then you can save yourself some money.
But then again I am a scientist for a living so I enjoy doing experiments on my poor defenseless JK
, you may be one to just find something that works and stick with it. 
Last edited by tpm152; Nov 9, 2010 at 05:45 AM.
JK Newbie
Joined: Mar 2010
Posts: 17
Likes: 0
From: NorthCentral PA
Hi, tpm152, that's good info, and kind of what I was beginning to suspect. I am also a scientist too, and JK experiments are so much fun... especially when they require field testing 
.
I see you're in State College- I'm in Williamsport. Maybe I'll see you up Pine Creek for a Jeep ride sometime.
I plan to run the gas down to nearly empty and then systematically try 87 from different gas stations around here. I've never had problems with Sheetz in my old Dodge truck but then i think that would have run on kerosene if I'd given it
Sunoco is the only "name brand" around here, but I guess that's good since I think they're a PA company to begin with.
Anyway, more data to be reported as I generate it.
Thanks!
.I see you're in State College- I'm in Williamsport. Maybe I'll see you up Pine Creek for a Jeep ride sometime.
I plan to run the gas down to nearly empty and then systematically try 87 from different gas stations around here. I've never had problems with Sheetz in my old Dodge truck but then i think that would have run on kerosene if I'd given it
Sunoco is the only "name brand" around here, but I guess that's good since I think they're a PA company to begin with.
Anyway, more data to be reported as I generate it.
Thanks!
JK Newbie
Joined: Mar 2011
Posts: 28
Likes: 0
From: Pottsville, PA
pics
I replaced the knock sensor today. Simple task (remove knock sensor bolt with 1/2 inch wrench; tug sensor gently until it pops off (no locking tabs or anything... just friction fit with friction tabs. Just pull.); install new sensor using same bolt. I also cleaned off the mounting surface before installing the new sensor).
Took it for a drive and instantly noticed more power, better response/acceleration; and any sign of pinging (which was rare) abruptly went away. I'm nearly convinced the sensor was bad.
A couple more variables were at work though:
a) I had added a bottle of Techron (carbon deposit cleaner) to the current tank, which was nearing empty again
b) I was driving much harder than before, and maybe the computer adapted to the new driving style
c) I switched gasoline brands; when tank was half full of Mobil + Techron, I filled the remaining half with Shell 89 octane. Drove it to about 1/4 full before installing the new sensor.
d) I went down a tire size, from 285/75 to 265/75, obviously reducing weight and rotational mass, which resulted in better response (also "easier" gearing)
Despite all that, I was still having knocking/pinging problems on every trip. Changing the sensor seems to have made a HUGE difference.
If anyone's got knocking/pinging problems, I suggest you try replacing the sensor (and switch gas brands, because it's so easy to do so). The part cost $18 and change from my local dealer.
My test drive was on the highway, to get things nicely warmed up. Ran it hard, tried passing, accelerating, downshift/accel, etc... all sorts of combos. I was so happy with the results that I did some mild wheeling at a couple spots on the way home -- including some near 45 degree ascents at a construction site with nice dirt/rock mountains and plateaus... again, the different between before and after was night/day.
My JK has 4,197 miles on it. All this time I've been thinking it was sluggish and underpowered and figured well that's just how the 3.8L Jeep is (this is my first Jeep). NOW I GET IT! There's actually POWER in this thing!!
I'm going right back to my 285's!
Couldn't be happier! It's like I have a new Jeep again!
Took it for a drive and instantly noticed more power, better response/acceleration; and any sign of pinging (which was rare) abruptly went away. I'm nearly convinced the sensor was bad.
A couple more variables were at work though:
a) I had added a bottle of Techron (carbon deposit cleaner) to the current tank, which was nearing empty again
b) I was driving much harder than before, and maybe the computer adapted to the new driving style
c) I switched gasoline brands; when tank was half full of Mobil + Techron, I filled the remaining half with Shell 89 octane. Drove it to about 1/4 full before installing the new sensor.
d) I went down a tire size, from 285/75 to 265/75, obviously reducing weight and rotational mass, which resulted in better response (also "easier" gearing)
Despite all that, I was still having knocking/pinging problems on every trip. Changing the sensor seems to have made a HUGE difference.
If anyone's got knocking/pinging problems, I suggest you try replacing the sensor (and switch gas brands, because it's so easy to do so). The part cost $18 and change from my local dealer.
My test drive was on the highway, to get things nicely warmed up. Ran it hard, tried passing, accelerating, downshift/accel, etc... all sorts of combos. I was so happy with the results that I did some mild wheeling at a couple spots on the way home -- including some near 45 degree ascents at a construction site with nice dirt/rock mountains and plateaus... again, the different between before and after was night/day.
My JK has 4,197 miles on it. All this time I've been thinking it was sluggish and underpowered and figured well that's just how the 3.8L Jeep is (this is my first Jeep). NOW I GET IT! There's actually POWER in this thing!!
I'm going right back to my 285's!
Couldn't be happier! It's like I have a new Jeep again!
Thread Starter
JK Enthusiast
Joined: Mar 2010
Posts: 364
Likes: 0
From: Maine
However, before going for the knock sensor, I'd first consider what the axle gear ratio is; how much weight has been added to the rig; and whether or not more rotational mass has been added (bigger tires and/or steel rims instead of alloys)
In the end, my gut feeling based on my experience (various combinations of 2010 & 2011, 2-door and 4-door, 3.73, 4.10 and 4.88 axle gears, 29.7", 32" and 33" tires) is that the problem was simply that the 3.8L was fine for a mildly-loaded, light duty rig, but when you start demanding more torque by loading it up, the motor gets bogged down.
I certainly don't mean by "light duty" that the JK isn't suitable for serious off-roading. In fact it's far superior for off-roading than the heavy duty pickup I replaced it with, and I miss my JK so much!... but I needed a tow rig and the JK just wasn't it for towing 3,300+ lbs, even after regearing.
Everything in life's a tradeoff.
JK Enthusiast
Joined: Oct 2010
Posts: 186
Likes: 1
From: Central Texas, Hill Country
I had a long battle with pinging. I did all the usual stuff like injector cleaner, new plugs, knock sensor, etc. What really made the difference is a regear away from 3.21s ( I was lugging the engine causing excessive carbon buildup) followed by two rounds of Mopar combustion chamber cleaner and some spirited driving to blow the carbon out. Its been good since then.
JK Newbie
Joined: Nov 2012
Posts: 17
Likes: 0
From: Canada
Only one knock sensor (4) is used. It is located on the right side of engine block, to the rear of right engine mount (3).
1.Disconnect negative battery cable.
2.Raise vehicle and support.
3.Disconnect electrical connector (1) from knock sensor.
4.Remove mounting bolt (2).
5.Remove sensor (4) from engine.
