Predetonation/spark knock

[Fizzlepop]

I've been having a recurring issue with what sounds like spark knock at lower RPMs. I've brought it to the dealer, and did a ride along with their senior tech on the issue, but because its intermittent, I had to more or less forcibly recreate the issue.

The speed limit from where I live to where I work is 20 mph with about 4-5 stop signs, and this seems to be where it happens most, always at lower RPMs. There will be a rattle in the motor for about 3-5 seconds on acceleration, and then it goes away. I can recreate the issue by pressing the gas, releasing the gas, and pressing it again. Now, I know that I'm recreating it because I'm confusing the computers VVT, but it's the only way I can reproduce the sound I'm hearing while the tech is with me.

It did not do this during the colder weather, and wont do it when the engine is cool, or even when its warm at first. After an hour or so of driving, though, it begins to do it.

I've fueled up at different stations owned by different companies, so im not convinced it's the fuel. I've also put 89 in instead of 87 with same results.

Has anyone else experienced this?

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[Biscuit]

Nope. Auto or manual? If manual, you should be no higher than second or third gear at 20 mph/~1500-2000 rpm; otherwise, you're lugging the engine

 

[xpsruler]

I'm contacting my dealer tomorrow to get the same issue looked at. Mainly seems to happen in 3rd gear when going up inclines. I use top tier 87 octane and have run 89 up to 91 as well with no luck.

Its a rattle type noise that may be knock but I'm not entirely sure.

 

[Fizzlepop]

I'm contacting my dealer tomorrow to get the same issue looked at. Mainly seems to happen in 3rd gear when going up inclines. I use top tier 87 octane and have run 89 up to 91 as well with no luck.

Its a rattle type noise that may be knock but I'm not entirely sure.

Mine is also almost always in third. I dont have hills, but because speed limit is only 20, I'm barely giving it gas when it does it.

 

[Fizzlepop]

Nope. Auto or manual? If manual, you should be no higher than second or third gear at 20 mph/~1500-2000 rpm; otherwise, you're lugging the engine

It's an auto.

 

[xpsruler]

It's an auto.

Mines an auto too.

 

[Fizzlepop]

Today it was more frequent, even in 5th.

 

[xpsruler]

How you explain it sounds very similar to what I'm experiencing. If I give the gas slight acceleration after letting off while coasting I hear it as well.

 

[Fizzlepop]

How you explain it sounds very similar to what I'm experiencing. If I give the gas slight acceleration after letting off while coasting I hear it as well.

Yep. I tried explaining that to the technician, and he told me I was confusing the computers VVT because it attempts to anticipate my driving habits.

Obviously this is not the case, as predetonation hasnt been an issue for years. Let me know if your dealer says something different, please.

 

[cabnfvr]

I've been having a recurring issue with what sounds like spark knock.... Has anyone else experienced this?

A few times, but very few and a very short lived event. I suspect it will be corrected with a future software update. Did 89 octane make a difference for you?

 

[Fizzlepop]

A few times, but very few and a very short lived event. I suspect it will be corrected with a future software update. Did 89 octane make a difference for you?

It did not, and with 91 being 70 cents more per gallon by me, I wasnt about to try it.

The rattling isnt long, 1-2 seconds on initial gas. Its frequent though.

 

[xpsruler]

Update: I brought my JL into the dealer and let them listen to it (during the test drive it was the least amount of noise the rattle ever made lol). The service rep who listened believes it may be a slight knock though. They found an update for the TCM I believe and ran that as a start to see if it will alleviate the issue. I heard it slightly on the way home but will give the Jeep some time with the update and see where it is at from there.

 

[xpsruler]

Well, I'm still hearing it... seems to be most prevelant when warm outside. The TCM update has definitely made my Jeep shift smoother so I'm at least happy about that. I will contact the service department and see what can be done.

Any updates from anyone else?

 

[jspagat]

Well, I'm still hearing it... seems to be most prevelant when warm outside. The TCM update has definitely made my Jeep shift smoother so I'm at least happy about that. I will contact the service department and see what can be done.

Any updates from anyone else?

I have the same issue... Auto....

Service department heard the knock. Scratched their heads and said... nuthin we can do about it...

 

[viper88]

Which engine, 3.6 or 2.0?

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