3.8 pinging
JK Jedi Master
Joined: Feb 2008
Posts: 12,907
Likes: 185
From: Maine
Thanks for the advice. I can buy the whole ECU learning thing. My Jeep primarily makes short low rpm trips which probably isn't the best scenario for the engine. I will try and borrow the scan tool and get a tech to show me what you just said and clear the adaptive learning tables.
As far as I know, only the transmission controller has adaptive learning.
Super Moderator
Joined: Jun 2011
Posts: 11,054
Likes: 85
From: Hendersonville, Tennessee
Originally Posted by ronjenx
Has it been established the engine control has adaptive learning?
As far as I know, only the transmission controller has adaptive learning.
Super Moderator
Joined: Jun 2011
Posts: 11,054
Likes: 85
From: Hendersonville, Tennessee
Originally Posted by bubba_zenetti
Sort of. The rear 02 sensors will possibly pick up an issue with it. The front 02 sensors are more important in dealing with fuel trim. The rears pretty much look at the levels of unburned HC leaving the pipe and has effect on fuel trim but not as great as the front ones do. As a matter of fact you can ditch the rear sensors all together and the vehicle will still operate.
Switch over to 10w40 and watch oil consumption go away. 5w20 is way to thin of an oil. From an energy consumption point of view its good. You get better protection out of 10w40 and the losses due to viscosity drag are so minute you really wont notice any drop in mpgs. Also keeps oil pressure up in the rod and main bearings that seem to have a high failure rate on these things.
Super Moderator
Joined: Jun 2011
Posts: 11,054
Likes: 85
From: Hendersonville, Tennessee
Originally Posted by itsajeepthing91
Disconnected battery installed new knock sensor no difference.
JK Junkie
Joined: Jul 2008
Posts: 3,017
Likes: 0
From: Lakewood, OH
OK, I'll throw in my two cents and hopefully without any pretension.
The PCM relearn process definitely occurs on both automatic and manual transmissions.
A PCM reset is definitely where to start if you experience pre-ignition. After a reset, drive the vehicle harder than normal, turning off the motor and restarting frequently. The PCM re-learn process is based on key cycles, as many as 50, so the more load you put on the engine the less likely pre-ignition will occur. Experiencing pre-ignition directly after a PCM reset is not an unlikely occurrence and I would dismiss it until I had at least a half dozen key cycles after placing a decent load on the engine.
Change of seasons and cooler weather definitely play a role. As soon as the temperatures drop below 60 my JK seems to scratch it's head with fuel trim. As the air gets denser with cooler temperatures there's a point where it definitely starts lugging. I personally use my programmer to do spring and fall PCM resets, changing octane settings and my thermostat.
Examine your IAT sensor. If it's oily, blocked or perhaps broken it can give you false temperature reads. Also check to make sure there's a good seal around the gasket. If your PCM doesn't know the intake air temperature it doesn't have a prayer of getting your fuel trim correct.
I also noted that one of the people experiencing pre-ignition is running a 3" exhaust. Not exactly sure if this is playing a role, but a 3" exhaust won't properly evacuate the cylinders. This means that an excess amount of spent exhaust gases remain in the cylinder, which also means they can't take on all the air/fuel intended.
The PCM relearn process definitely occurs on both automatic and manual transmissions.
A PCM reset is definitely where to start if you experience pre-ignition. After a reset, drive the vehicle harder than normal, turning off the motor and restarting frequently. The PCM re-learn process is based on key cycles, as many as 50, so the more load you put on the engine the less likely pre-ignition will occur. Experiencing pre-ignition directly after a PCM reset is not an unlikely occurrence and I would dismiss it until I had at least a half dozen key cycles after placing a decent load on the engine.
Change of seasons and cooler weather definitely play a role. As soon as the temperatures drop below 60 my JK seems to scratch it's head with fuel trim. As the air gets denser with cooler temperatures there's a point where it definitely starts lugging. I personally use my programmer to do spring and fall PCM resets, changing octane settings and my thermostat.
Examine your IAT sensor. If it's oily, blocked or perhaps broken it can give you false temperature reads. Also check to make sure there's a good seal around the gasket. If your PCM doesn't know the intake air temperature it doesn't have a prayer of getting your fuel trim correct.
I also noted that one of the people experiencing pre-ignition is running a 3" exhaust. Not exactly sure if this is playing a role, but a 3" exhaust won't properly evacuate the cylinders. This means that an excess amount of spent exhaust gases remain in the cylinder, which also means they can't take on all the air/fuel intended.
Thread Starter
JK Enthusiast
Joined: Dec 2009
Posts: 384
Likes: 1
From: Canada
OK, I'll throw in my two cents and hopefully without any pretension.
The PCM relearn process definitely occurs on both automatic and manual transmissions.
A PCM reset is definitely where to start if you experience pre-ignition. After a reset, drive the vehicle harder than normal, turning off the motor and restarting frequently. The PCM re-learn process is based on key cycles, as many as 50, so the more load you put on the engine the less likely pre-ignition will occur. Experiencing pre-ignition directly after a PCM reset is not an unlikely occurrence and I would dismiss it until I had at least a half dozen key cycles after placing a decent load on the engine.
Change of seasons and cooler weather definitely play a role. As soon as the temperatures drop below 60 my JK seems to scratch it's head with fuel trim. As the air gets denser with cooler temperatures there's a point where it definitely starts lugging. I personally use my programmer to do spring and fall PCM resets, changing octane settings and my thermostat.
Examine your IAT sensor. If it's oily, blocked or perhaps broken it can give you false temperature reads. Also check to make sure there's a good seal around the gasket. If your PCM doesn't know the intake air temperature it doesn't have a prayer of getting your fuel trim correct.
I also noted that one of the people experiencing pre-ignition is running a 3" exhaust. Not exactly sure if this is playing a role, but a 3" exhaust won't properly evacuate the cylinders. This means that an excess amount of spent exhaust gases remain in the cylinder, which also means they can't take on all the air/fuel intended.
The PCM relearn process definitely occurs on both automatic and manual transmissions.
A PCM reset is definitely where to start if you experience pre-ignition. After a reset, drive the vehicle harder than normal, turning off the motor and restarting frequently. The PCM re-learn process is based on key cycles, as many as 50, so the more load you put on the engine the less likely pre-ignition will occur. Experiencing pre-ignition directly after a PCM reset is not an unlikely occurrence and I would dismiss it until I had at least a half dozen key cycles after placing a decent load on the engine.
Change of seasons and cooler weather definitely play a role. As soon as the temperatures drop below 60 my JK seems to scratch it's head with fuel trim. As the air gets denser with cooler temperatures there's a point where it definitely starts lugging. I personally use my programmer to do spring and fall PCM resets, changing octane settings and my thermostat.
Examine your IAT sensor. If it's oily, blocked or perhaps broken it can give you false temperature reads. Also check to make sure there's a good seal around the gasket. If your PCM doesn't know the intake air temperature it doesn't have a prayer of getting your fuel trim correct.
I also noted that one of the people experiencing pre-ignition is running a 3" exhaust. Not exactly sure if this is playing a role, but a 3" exhaust won't properly evacuate the cylinders. This means that an excess amount of spent exhaust gases remain in the cylinder, which also means they can't take on all the air/fuel intended.
Thread Starter
JK Enthusiast
Joined: Dec 2009
Posts: 384
Likes: 1
From: Canada
Originally Posted by bubba_zenetti
On a side note, anyone ever check their drivers side exhaust manifold for a crack? Everyone here keeps saying it sounds different from pining. You would be very surprised to know that some of them seriously sound like a small ball peen hammer hitting the manifold which seriously sounds like pre-ignition. Since we have no CELs getting thrown here I would seriously be ruling that out. Its 3 nuts and the heat shield is off. Does not hurt to look. They all crack at the between the forward runners. Sometimes it is very hard to see it but if you see a hairline on it, its cracked.
Thread Starter
JK Enthusiast
Joined: Dec 2009
Posts: 384
Likes: 1
From: Canada
Originally Posted by bubba_zenetti
Cool so now we can assume it is not that at all.
If you are dumping higher octane fuel in your machine and it goes away then indeed you have some sort of spark management issues. I think this is pre-ignition not detonation (they are two separate types of knock).
Detonation is caused by the AF mixture getting too hot and lighting off from just compressing the mixture. This would occur at all times under a load and is super destructive. You will more than likely know when this is happening.
Pre-ignition is when the spark lights off the fuel and the flame propagation begins but on the other side of the combustion chamber there is also another flame front being started and it is colliding with the original front. This is what happens when cylinder pressure rises to sharp and too early(spark too advanced). This is what you got going on more than likely. Overheating, too lean of a fuel mixture and improper spark timing are the causes of this.
You are not likely running too lean but your CAI may be causing a lean condition under load which will raise combustion temperatures up. Put your stock airbox on it and see if it goes away.
One thing that can cause this, but it is a long shot is a malfunctioning EGR. If the EGR is not circulating properly, combustion temperatures will go up and you get knock.
Sea foam wont do shit. It garbage. If you suspect it is carbon deposits, use BG44k. That shit really works but it is pricey at $25+ a can.