Originally Posted by m998dna

And if the combustion chamber got hot enough it could diesel (run on) when you turned off the motor ... because that's how diesels work.

Originally Posted by therza

Have heard the diesel reference a couple of times now. I have had cars that had terrible dieseling issues. But I don't see how that is possible in a modern, fuel injected motor. In the old days, the carburator was full of fuel so it could continue to feed the dieseling motor. In addition, the fuel pumps were mechanical so as long as the crankshaft was turning, it would feed fuel into the carb. With modern engines, when you turn the key off, the injectors are closed. Period. Unless they are leaking AND you have carbon build up, I don't see how dieseling could occur. In addition, turning the key off shuts the fuel pump off. Now there is residual pressure in the fuel line, but the injectors are "locked" in the closed position. What would be the fuel source for dieseling??? I think my point is that you could have carbon build up without dieseling. But BG44K would remove it. It works!

Originally Posted by m998dna

I agree 100%... and I'm glad you've clarified this. I haven't heard detonation or dieseling on a gas motor in over 20 years.

This motor has been running on the edge for 55,000000KMs or whenever he started opening up the air intake and exhaust and now carbon build up has increased the compression ratio which is probably causing detonation... however one would think the timing would retard itself through adaptives... I don't know.

He could have a failing sensor.. I would run this stuff you mentioned and if that doesn't work then his electronics are probably hosed or the noise is something different.

I feel his frustration and appears to be walking in circles.

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Originally Posted by itsajeepthing91

I'm hoping the culprit is dirty injectors and that after I run this tank out all will be well if not I ordered a knock sensor and that's where I'll start

Originally Posted by bubba_zenetti

Your crank position sensor. From there the ECU figures out torque doing a little math. In actuality, its reading off the flex plate. There is a ring around it that produces a hall effect. That ring slips over the converter as it is bolted to the flex plate.

Originally Posted by bubba_zenetti

You would be correct.

From there it calculates shift schedule, torque management for the transmission on automatics, etc. In the 6 speed I have no idea if there is adaptive learning the same way the automatics do it.

But my theory on this whole thing if it is truly pining is that it probably is not carbon buildup. If it was it would ping more under WOT as it would be getting even hotter then. That and its going to ping no matter what in most cases not come and go.

Since this pinging in one case is under a load but not WOT it would be safe to assume that the timing advance might be too steep in the timing curve. You have base spark and spark advance, where the timing is at idle and where it is going when you step on the skinny pedal. If base spark is up to high the timing curve is steep and it will ping until the motor gets up to speed. Kinda like having a spring break off the weights on an old distributor, the timing goes advance way to fast and it pings. But in the case where the computer is in control, it keeps advancing timing, detects best power output/most efficient burn and stops when it detects some sort of event such as torque drop off, knock sensor event or the o2 sensor tells it to back off a tad.

So with the 6 speed I am pretty sure it has some sort of adaptive learning table for the timing. It probably is not fast enough to learn changes in driving style. Since there is no way in hell one can let out the clutch and step on the gas every single time, the ECU is constantly changing the timing and its not always relearning fast enough. Only a theory but if one were to datalog the ignition timing I bet you might notice something there. Perhaps this is why its guys with 6speeds and not autos.

In order for you to erase the adaptive learning tables you need to discharge the capacitors inside the ECU that maintain last stored parameter data. Simply ground the positve battery terminal for a good 10 minutes or more. Then turn on the key and step on the brake pedal a few times. Just DCing the battery wont do it, it needs to be completely discharged or it will still store it. Or if you have access to a Snap On Versus or Mopar Star Scan you can reset the tables there for sure. The battery cable trick does not always work.

But yeah, thats about what I would be trying at this point. Not convinced it is carbon buildup, just bad timing management. There are motors out there with wayyyyy more carbon buildup than a JK with 16k on it and they do not have issues like this that often. This is because your ECU is suppose to take care of little issues like that for optimal clean air coming out of the tail pipe as out government mandates.

Of course it never hurts to clean out carbon. BG44k WORKS. The rest of it, Techron, Seafoam, Berrymans is all junk at best. BG44K seriously is voodoo black magic. I never use chemical fixes for good old fashioned cleaning because in 30 years of wrenching, I know that there is no substitute for just taking it apart and cleaning it. I with my own eyes watched this stuff clean the tops of pistons by sticking a bore scope in a spark plug hole and I kid you not a motor with 50k on it had shiny piston tops after one treatment. It also cleans injectors.

Cost. $25 -$50 a can online.

Originally Posted by bubba_zenetti

You could not be any more wrong. Just a small FYI, I am a 33 year veteran of the powersports industry and shop owner. I have built winning race motors and have a very good understanding of what preignition is all about. And it is surely not caused by dirty oil, thin oil, plugged PVC valves and too much air in the tires.

An exhaust leak has a metallic rapping sound if it coming from a crack. It can be confused for pinging. It can come and go as it heats up and seals the crack from heat expansion. Of course this is just an educated guess on what the sound could be as a modern vehicles are not likely to preignite fuel mixtures. There are too many fail safes that would prevent it from preigniting in the first place. A JK with a cracked exhaust manifold will make pining sounds (what do I know, I have only replaced 4 sets this year.)

If a plug is fouled it will not fire. If it does not fire, there is no ignition source to cause detonation unless there is a hot spot in the combustion chamber. In which case it will probably diesel (run on) after the key is turned off. Plug fouling will never cause detonation or preignition.

A clogged PCV valve will not cause plugs to foul. It will cause seals to start leaking from excessive pressure in the crankcase. It plays absolutely no role in the combustion process outside of recycling crankcase vapor and it is merely a one way valve to suck blow by out of the crankcase and route it back into the combustion chamber so that any unburned HC trapped in the crankcase will be burned. If anything a clogged PVC valve will lessen plug fouling as it is not going to be dumping anything into the combustion chamber for recycling. You could vent the PVC to the atmosphere (how mine is set up) and the vehicle could care less.

A sign of preignition is bone white plug tips that may be blistered and cracked. Melted electrodes are definitely going to show up in extreme cases. But there is no way you can run too lean without your JK knowing about it. If target AFR moves to far past 14.7:1 the ECU will log it and throw a P0171 and P0172 codes indicating that the fuel mixture is too lean on the left and right bank. So unless you have that, you are probably not too lean. Pull your plugs and look at them.

Preignition sounds like marbles dropping in a coffee can and it is pronounced under a load. You will KNOW when you are pinging. In this day and age not many people will know that sound because it just does not happen unless you own some old POS from the 80s or earlier. So with the OP trying so many random things to cure the problem, how do we even know if the OP knows what pinging really sounds like? Rod bearings failing, timing chains slapping the case, exhaust leaks have all brought me customers who thought their motorcycle was pinging but in fact it was something else.

Just saying ya know

Originally Posted by bubba_zenetti

BG44k is going to clean it up. It may stop the pre-igntion but your real issue is poor spark management. On a modern vehicle, carbon buildup should never be a real issue because the entire fuel management system should be making sure that everything is always optimal. Think about if for a sec, if every car gets carbon buildup in it, then they would all knock. Well they really cannot have that happening so there are measures built in to control these problems. To some degree, too much carbon and yeah none of this matters any more but its just not that big of an issue with <100k motors unless something is not right with spark timing.

There are way too many factors that control spark timing, not just how you drive and how it learns. Readings from the 02 sensor, the MAP sensor, your engine coolant temp, the only real way to find out is datalog it a bit and see just exactly what it is doing.

If you do have access to Starscan, find some way to clear the adaptive learning tables and see if that gets rid of it. Sometimes the ECU learns something that is not right. The cheap power mod, clear it out, get 4 or more of your largest friends in the Jeep and drive the piss out of it as hard as can up a hill or something. This will cause it to re learn your driving habits and trim for best power. But I would just clear out the tables and drive it normal and see if the problem goes away.