3.8 pinging
JK Enthusiast
Joined: Mar 2011
Posts: 139
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From: Fort Walton, Fl
Well it appears we have some shade tree mechanics in here that have very little understanding of what's really going on. Just to throw this out "many of you don't know" Chrysler did a an extensive research campaign to develop the award wining power horse (aka 3.8). I hate to embarrass anyone... All of you guys had good ideas but it's obviously (painfully obvious) the flux capacitor that is out of time. It's the jeeps way of say you need 2more inches of lift or 2inch biggr tires. Try the lift then the tires and I bet you don't hear the ping anymore...
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JK Enthusiast
Joined: Dec 2009
Posts: 384
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From: Canada
Originally Posted by jaxx1671
Well it appears we have some shade tree mechanics in here that have very little understanding of what's really going on. Just to throw this out "many of you don't know" Chrysler did a an extensive research campaign to develop the award wining power horse (aka 3.8). I hate to embarrass anyone... All of you guys had good ideas but it's obviously (painfully obvious) the flux capacitor that is out of time. It's the jeeps way of say you need 2more inches of lift or 2inch biggr tires. Try the lift then the tires and I bet you don't hear the ping anymore...
Super Moderator
Joined: Jun 2011
Posts: 11,054
Likes: 85
From: Hendersonville, Tennessee
Originally Posted by jaxx1671
Well it appears we have some shade tree mechanics in here that have very little understanding of what's really going on. Just to throw this out "many of you don't know" Chrysler did a an extensive research campaign to develop the award wining power horse (aka 3.8). I hate to embarrass anyone... All of you guys had good ideas but it's obviously (painfully obvious) the flux capacitor that is out of time. It's the jeeps way of say you need 2more inches of lift or 2inch biggr tires. Try the lift then the tires and I bet you don't hear the ping anymore...
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JK Enthusiast
Joined: Dec 2009
Posts: 384
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From: Canada
Originally Posted by Ryan0260
Unfortunately bigger tires will put more load on the motor which will only make the spark knock worse. This is from experience
Super Moderator
Joined: Jun 2011
Posts: 11,054
Likes: 85
From: Hendersonville, Tennessee
Originally Posted by itsajeepthing91
But at least you look that much cooler when your driving down the street while your jeep pings away haha
JK Enthusiast
Joined: Mar 2011
Posts: 139
Likes: 1
From: Fort Walton, Fl
Really? Really? I beg to differ sir... The 3.8 will laugh at engine ping when it out fitted with 37" or bigger. Its Chrysler's way of saying, "thank you sir for bring the HP down out of the stratosphere!" now you don't have to worry about spinning out and getting those racing tickets from the cops! 35" are a good start my friend... And even if the ping continues, well... It looks bad azz! Also you wife may buy the reason for the tires!
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JK Enthusiast
Joined: Dec 2009
Posts: 384
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From: Canada
Originally Posted by bubba_zenetti
Actually they are quite random. And if you know it is pinging, then you know that pinging is not caused by fouled spark plugs, bad wires or even a bad knock sensor. So what I am saying is if you have no idea what REALLY causes pre-igntion (because by the way you are troubleshooting this you really don't have a clue.) Then perhaps you really do not know what the sound of true pinging is and you may be mistaking it for something else like the all too familiar cracked exhaust manifold that believe it or not sounds just like pinging under certain conditions and its sound is not always present.
So yeah, I have a lot to contribute to this thread that actually makes sense, is not random and comes from a bit over 30 years as a professional mechanic who knows better. Take it how you want, I am just trying to help you so ya do not need to be a dick about it by telling me not to post in your thread. However if you want a bunch of random answers by people who do not do this for a living.............
Why did it stop pinging after you poured octane booster in it, well it is possible you got bad gas and your problem really was pre-ignition, its possible it is all coincidental. But from how you are trying to resolve the issue, you are attacking areas that are not even precursors to pre-ignition with the exception of carbon.
But had you read anything I said, you could probably start deducting things by process of elimination:
1) Does it run on when you shut down the engine? NO. Then its not carbon buildup in most cases.
2) Does it throw codes P0171 or PO172? NO then its not too lean
3) Are your plugs blistered and white? NO? Then it is probably NOT preigntiing and it is probably not running lean.
4) Did you even remove the heat shield from the driver side manifold?
Ryan0260, Your friend may very well have an exhaust leak that sounds different. My exhaust leak sounded just like a small hammer hitting my exhaust manifold. The 3 others I replaced this year on friends JKs sounded like mine or sounded like your typical leak. It does not always sound the same! Before you decide to discard such info, you may want to take note that MANY exhaust leaks that emanate from the head area of a vehicle through a very small crack can have a metallic rapping sound that will often mimic detonation to most people. Wanna find a resolution, well then perhaps you might want to have a quick peek. If not then I suggest your only REAL resolution is find someone who has an aftermarket tuner such as the Predator, plug it into your OBDC port and datalog the following SHORT TERM KNK RETARD and LONG TERM KNK RETARD. Romp on the thing and see what those two PIDs throw out. That will tell you if you are pulling spark due to pre-ignition. If you are then you can start looking at ignition timing issues. I seriously doubt it is a lean condition issue as the ECU will pick it up and return CELs that indicate too lean P0171/171. Even if it was a minor lean condition the JK uses closed loop control of fuel trim so its going to self correct itself. At this point I would be looking at timing issues and check the base spark and spark advance PIDs on a Predator or like device.
The only reason why I am throwing out the cracked manifiold is because none of your findings with the spark plugs, no codes and such make it difficult for me to think that pre-ignition is the culprit here. I am not here to argue with either of you who is right or wrong, but damn guys, I do this for a living, I know the ins and outs of internal combustion engines, and honestly trying to troubleshoot a problem over the internet the only thing you can do is go by what facts you have at hand, no blistered plugs, no CELs and knowing what I know about how FI systems work, pre-ignition right now does not make any sense. Start looking at other things first to eliminate them from the equation.
Out of curiosity do either of you experience a loss of power when you feel the pining occurring?
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JK Enthusiast
Joined: Dec 2009
Posts: 384
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From: Canada
Also should note that it's not a coincidence I have been fighting this for almost 2 months and 1-2 tanks a week and the only way to cure is more octane. I did plugs and wires first because it was an easy try and good maintenance. You're right fouled plugs won't cause pre ignition but plugs without the proper gap will. Next I tried cleaning carbon out. Now I'm going to try knock sensor that one I will agree is random but talked to a couple mechanic friends and a bit of googling and although highly unlikely I'm going to give it a shot. Have you ever heard the saying "it's not what you say it's how you say it" you didn't say are you sure it's preignition because a crack in the exhaust manifold (checked manifold today its not cracked) sounds very similar you threw me under the bus saying something a long the lines of how can we be sure this guy has a clue of what he is talking about. I felt you were being a dick just as much as you feel I am. Nothing I have done has been "random" so instead of Basically saying jeeps can't ping you don't know what youre talking about just drop it.
JK Enthusiast
Joined: Oct 2010
Posts: 186
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From: Central Texas, Hill Country
I've subscribed to this because I have a 2008, 6speed, and it also pings. it started at 10k miles. I now have 40k on it. I did all those things you mentioned: new plugs, knock sensor, sea foam etc. The only thing that improved it is a gear swap. I was lugging the engine w/ 33s and3.21s. When I swapped gears most of my pinging went away except it still pings a little right at 2300 rpm but that's about it. Better gas helps. I just live with it. If it dies prematurely I'll get an Aev hemi kit and junk the 3.8
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JK Enthusiast
Joined: Dec 2009
Posts: 384
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From: Canada
Originally Posted by bubba_zenetti
Its all how you read it. Its the interweb. There are no emotions:P All I was saying is what evidence do we have that the OP even knows for sure it is preignition problems. Anywayssssssssssssss
So if this has been an ongoing battle for two month (more info we did not have) Yeah I definitely would check that just for kicks. Not only will it make awful noise that can be totally random, it will screw with your fuel and timing maps as now the 02 sensor is reading screwball.
But none the less you do have a problem. Back to the question, do you notice a loss of power when you hear the pre-igntion/detonation going on (these are two different things and an answer might better resolve this matter)?