Another spark knock thread... sorry

[Old Jeeper]

Dude you can't compare a 20 year old straight 6 to the modern pentastar. I don't think they even share design elements. Like nothing is even remotely the same

That being said I'm pretty sure there's not only a PCM update for it but also a TSB to replace the PCV valve for excessive spark knock (especially when already running 91 octane)

Well DUDE I hate to break the news but Spark Knock has been around longer than. even I have been alive for all of the same reasons it was then, it is today. We can go back to the days of Model Ts and As and on the steering wheel of some of them was how you adjusted the spark to not knock!

In my days if you had GM engines, most of the V8 you adjusted the spark by loosening and turning in the distributor by hand or if you could afford it a timing light.

Learn something new every day...

Sponsored

 

[dstrahm]

My ‘21 JLUR has had the preignition knock (AKA Spark knock) for several years. Hardly noticeable in cool weather driving in the flatlands but very noticeable at higher altitudes pulling a slight load on the trails. Local dealership finally found a TSB referencing the issue. It’s caused by deposits on the head and top of piston due to substandard fuel. I’ll scan the TSB tomorrow and post. It is common for spark knock to subside with higher octane fuel but I’m not willing to run high test at current prices!

So what does the TSB offer as a fix? Remove the heads and clean the combustion chamber and piston head. Wow! Almost 12 hours of warranty labor! I didn’t really want my engine taken apart, but the knock will only get worse with age, so it’s scheduled for next week.

And what is and where do you get the better gas. This article gives some ideas.
https://www.consumerreports.org/car...r-gasoline-worth-the-extra-price-a7682471234/

 

[Byrds8]

In my days if you had GM engines, most of the V8 you adjusted the spark by loosening and turning in the distributor by hand or if you could afford it a timing light.

Learn something new every day...

Man those were days! My first ride, 1979 Camaro, I had to do exactly that. To this day I still miss her. If not wrecked back in 94, she would be in the garage instead of my Jeep.

 

[Byrds8]

Man those were days! My first ride, 1979 Camaro, I had to do exactly that. To this day I still miss her. If not wrecked back in 94, she would be in the garage instead of my Jeep. Before I had to replace the engine, there was a time I would turn the car off and walk away and it would still be half ass running lol.

 

[badge171]

I had the same issue with spark knock on my 3.6
The first time I herd it was on a steep hill off road
What fixed it for me was installing a UPR oil catch can
It removes 98% of oil mist that would normally enter the combustion chamber degrading the air fuel mixture. I have not herd one ping after installing the catch can
What I liked about the UPR is it is easily removable if you have to take it to the dealer
Another upgrade I installed about two mouths ago was the RpmExtreme Jeep jl fan controller

http://www.rpmextreme.com/Product/311/Jeep-JL-PWM-FAN-CONTROLLER.aspx

It lowered my coolant and oil temps by 25 to 30 degrees and to my surprise also reduced the amount of oil that the catch can was collecting (less oil mist in the crank case)
On the left before RpmExtreme Jeep jl fan controller
On the right after the RpmExtreme Jeep jl fan controller

 

[badge171]

I too installed a catch can on my 22 Rubicon 3.6, I do my own service, I usually dump the oil 4-5k miles what surprised me was I had about 2000 on the oil I started the Jeep up one morning and it started missing. It took a few minutes to clean out, and I got the smell of burnt oil . Got home . Checked the can ,overfilled with oil ! Not sure if I have something wrong with that amount of oil in the can or not? But now it's 1000 mile dump for me.

 

[Willys41]

I always emptied mine at about 1k also and was surprised on how much oil there was in the can
Another 400 miles I will be checking it again
This time it will be with the fan controller installed
I will let you know the results

 

[Old Jeeper]

Those were days. I could take one hand full of tools, combo open end and wrenches, and remove the transmission from my car.

I remember one time back in my college days my Corvette had broken off some teeth on the flywheel. So I bump start it by clicking the key until it engaged and started right up. So I saved my money over about a year or so and not have a lot of time on my hands I went to a GM shop in town and I had saved up enough coins to replace the Flywheel, clutch, pressure plate and throwout bearing.. Shop said they have it out in a couple of days.

A week later I still did not have my car. Wed afternoon was my short day in college and I dressed up to go to the funeral of a friend's dad. Then I swung by the shop and I got the real story, they could get the trans out of car (Muncie 4 sp Stick). I said WHAT? Jack it up so I roll under it and take it out. The Mech looks at me and I had taken off my sports coat, but have a white shirt...you gonna get dirty! I rolled up my sleeves rolled under and rolled out with the transmission on my chest, all the mechs were shocked. Turns out all of them could not get it out in a week and a half. Took me all of about 3 min.

LOL there is actually a technique to getting it out and I learned years before on Corvettes, and I had learned the trick.

Speaking of turning the distributor, there a better way.

Put you car in gear (stick trans) and back it up not running. Take 2 to do this and back up your car till the timing degree wheel on the front of the engine just goes slightly past how many degrees BTDC you want. Then go to the rear of the car and push forward to stop exactly on degrees you want run.

NOW go to your distributor and turn it until the points close, now lock it down and you will prob never need to change your timing again. Just make sure you get the distributor bolted down tight.

 

[Byrds8]

Those were days. I could take one hand full of tools, combo open end and wrenches, and remove the transmission from my car.

I remember one time back in my college days my Corvette had broken off some teeth on the flywheel. So I bump start it by clicking the key until it engaged and started right up. So I saved my money over about a year or so and not have a lot of time on my hands I went to a GM shop in town and I had saved up enough coins to replace the Flywheel, clutch, pressure plate and throwout bearing.. Shop said they have it out in a couple of days.

A week later I still did not have my car. Wed afternoon was my short day in college and I dressed up to go to the funeral of a friend's dad. Then I swung by the shop and I got the real story, they could get the trans out of car (Muncie 4 sp Stick). I said WHAT? Jack it up so I roll under it and take it out. The Mech looks at me and I had taken off my sports coat, but have a white shirt...you gonna get dirty! I rolled up my sleeves rolled under and rolled out with the transmission on my chest, all the mechs were shocked. Turns out all of them could not get it out in a week and a half. Took me all of about 3 min.

LOL there is actually a technique to getting it out and I learned years before on Corvettes, and I had learned the trick.

Speaking of turning the distributor, there a better way.

Put you car in gear (stick trans) and back it up not running. Take 2 to do this and back up your car till the timing degree wheel on the front of the engine just goes slightly past how many degrees BTDC you want. Then go to the rear of the car and push forward to stop exactly on degrees you want run.

NOW go to your distributor and turn it until the points close, now lock it down and you will prob never need to change your timing again. Just make sure you get the distributor bolted down tight.

Funny the stories we have. Around '91 or '92, I was heading out with a date. All of a sudden I hear all this clanking coming from the engine. I pulled over on the side of the road, grab some tools, pop the passenger valve cover off and see a rocker arm laying over on its side. Throw the cover back on drive to Autozone and grab a new one. About 10min later, we are out on our date. It was so easy to work on the car. I actually have a few crazy stories with that one.

 

[Old Jeeper]

Funny the stories we have. Around '91 or '92, I was heading out with a date. All of a sudden I hear all this clanking coming from the engine. I pulled over on the side of the road, grab some tools, pop the passenger valve cover off and see a rocker arm laying over on its side. Throw the cover back on drive to Autozone and grab a new one. About 10min later, we are out on our date. It was so easy to work on the car. I actually have a few crazy stories with that one.

Those were the days my friend and we thought they would never end...

 

[Dusty Dude]

My ‘21 JLUR has had the preignition knock (AKA Spark knock) for several years. Hardly noticeable in cool weather driving in the flatlands but very noticeable at higher altitudes pulling a slight load on the trails. Local dealership finally found a TSB referencing the issue. It’s caused by deposits on the head and top of piston due to substandard fuel. I’ll scan the TSB tomorrow and post. It is common for spark knock to subside with higher octane fuel but I’m not willing to run high test at current prices!

So what does the TSB offer as a fix? Remove the heads and clean the combustion chamber and piston head. Wow! Almost 12 hours of warranty labor! I didn’t really want my engine taken apart, but the knock will only get worse with age, so it’s scheduled for next week.

Back in my younger days, I used to spray a small stream of water with a spray bottle in the engine while at part throttle. The RPM’s would drop, the engine would stumble, and the exhaust would blow out a huge pile of steam and soot. Followed up with an oil change and that ended the problem.

I have a feeling that if I tried that today, it would work just as well, but it would drive the computer nuts and throw codes all over the place. One more step to do, having to clear all the codes…

 

[dstrahm]

Back in my younger days, I used to spray a small stream of water with a spray bottle in the engine while at part throttle. The RPM’s would drop, the engine would stumble, and the exhaust would blow out a huge pile of steam and soot. Followed up with an oil change and that ended the problem.

I have a feeling that if I tried that today, it would work just as well, but it would drive the computer nuts and throw codes all over the place. One more step to do, having to clear all the codes…

Been around long enough to remember all of the shadetree cures for carbon buildup. I’d try that if it was out of warranty before taking the heads-off approach advocated by Jeep.

 

[Willys41]

My had spark knock right out the door brand new
UPR oil catch can solved it

 

[Dusty Dude]

My had spark knock right out the door brand new
UPR oil catch can solved it

Good to know. I have one waiting to be installed if my Jeep ever gets here.

 

[zakaron]

OP, what is your oil consumption like? I've found, even with 21K miles, I was down just under 1/2 way on the hash marks on the dip stick from an oil change only 1300 miles ago. To me that seems like a lot, so I have the Mishimoto catch can installed and just dumped 2oz after checking the oil. All that oil getting sucked back into the intake will lower the effective octane rating once mixed in with the air/fuel mix. Not only that, but the oil getting burned, over time, can create hot spots on the tops of the pistons. This only makes the pre-detonation condition worse.

I have read about a revised PCV, so it may be worth looking into to prevent some of that oil blow by from getting ingested if you are hesitant on a catch can:
https://www.jlwranglerforums.com/forum/threads/new-version-of-pcv.113454/

Sponsored