My engine is knocking/pinging on 87/89 octane

[krupa33]

When I run 87 octane or even 89 (up to the avg. of 15% ethanol), the motor pings and knocks at complete random RPM's, but absolutley ALWAYS does it when the engine is under a load. For example: it's a manual, so when im in first gear, go to about 9-10 mph, shift into 2nd gear, disengage the clutch and give it some throttle, its a pretty loud ping/knock that will last approximately 1 full second until torque has developed and there's no longer a stressful load on the engine. However, at any random time, no matter what gear or MPH, it will ping or knock. The only time it doesn't do this is when it is VERY cold (I live in PA), or when i am at highway speeds. There are absolutley no CEL's. The knock sensor isnt even picking it up. The motor is completely stock. 51,000 miles. I have OCD and change the oil every 3000 miles with AMSOIL 0-20 and a WIX filter. I always let this motor warm up to 120+ degrees before driving, and baby it until it reaches fully operating temperature (coolant and oil). Oil pressure is constant a 31 PSI. I have also did a smoke test to check for any vacuum leaks and could not find any. It also does not ping/knock when revved up in neutral or at idle.

I thought for the longest time that it was a loose nut/bolt rattling around the frame or engine bay, and i searched for a "rattle" (which is the only way to describe the sound if i didn't find out later it was in fact engine ping/knock), and i couldn't find shit. i looked under that engine and inside the frame holes and checked every single nut and bolt that was exposed enough for me to touch and made sure they were at the least finger tight and not moving around. i thought maybe the vibration in that specific RPM/throttle % zone would cause a vibration throughout the chassis/engine and it was just rattling a rock or nut or bolt or something.

Fast forward to July 4. The gas station chain (Sheetz) was selling gas, in any octane, for $1.776. I was 25 miles to empty, so i filled with 93 octane. i drove home (~2 miles) and motor was still pinging. Parked it and haven't drove it...

Until yesterday. Not only did I notice NO knocking/pinging whatsoever, the entire thing runs so much smoother. No matter what load i put on the engine, how low my rpm's were, how high the gear was, it NEVER knocked or pinged one time, and it was 91 degrees here.

Heres my questions:
1 - How do i fix this? I have an aftermarket warranty, but would they replace the engine or re-tune this?
2 - Before posting this I've read threads and people say this is common? and that FCA/Jeep said to just run 91+ and keep it above 2k RPM's? is this true? this vehicle is not REQUIRED to run 91+ octane, and i would imagine there would be a recall for an engine re-tune considering this cant be good for the motor?

I can try to post video of this noise, but my doors/top is off at the moment. I can link videos extremely similar to the noise it makes that i have found on youtube if that helps.

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[Left Field]

The rattling nut or washer is an apt description.
Carbon build up in the cylinders is a common source of detonation (pinging).
The most common cause of carbon build up is the ingestion of oil vapor from the crankcase.

This can be cause by a failed PCV valve or by an internal intake manifold leak.
If your engine is consuming some oil between changes these would be candidate reasons. With a 3000 mile OCI you might not notice minor oil consumption.

A simple check you can do for an internal intake leak is to disconnect the PCV valve and cork both openings. Then remove the oil fill cap, start the engine and use a small flap of paper to cover the oil fill opening. If it sucks down, you have a leak. If it flaps up and down or lifts, no leak or a very small leak - likely no problem.

The PCV valve is not particularly expensive, you might just replace it to eliminate it from the equation.

To stop the carbon induced pinging a good method is to use a combustion chamber carbon remover product, ensuring that it is safe for the catalytic converters and O2 sensors. If the pinging goes away after using the carbon remover you've at least identified the reason for it.

On a recent vehicle I did the internal leak test, it failed and I took it to the dealer for repair (a new gasket & the carbon remover). So likely could be covered by a warranty.

LF

 

[Xcoaste]

I don't have a great answer to your question, but instead of running a higher octane fuel, try running top tier fuel. I am also from PA and never use Sheetz gas. If you aren't familiar with top tier fuel, do a quick Google. It will give you a list of nearby stations.

Might not solve your issue but worth a shot.

 

[JeepinPete]

Mine does this during the summer, but only very briefly when loafing around the back roads. Last summer the Wawa in the area added ethanol free pumps. Gave it a try to see if MPG's would improve at all (they didn't). The side effect was my knocking went away for the rest of the summer. I have no logical reason why this would be, but it is what happened. When things started warming up this year, the ping was back, but I have been doing mostly highway driving so do not notice it nearly as much.

Pete

 

[Nvdardx28]

I don't have a very well defined scientific experiment to make a claim on my results but I had added one of those aftermarket catch cans to help eliminate the blow-by on the higher compression V6 and it had seemed to eliminate most of the pinging that I was experiencing. Sometimes I forget to empty the catch can and I am reminded by the pinging starting up again. I empty the catch can and the pinging goes away.

I tried running higher octane fuels in the past and only saw very mild improvements.

 

[Old Jeeper]

When I run 87 octane or even 89 (up to the avg. of 15% ethanol), the motor pings and knocks at complete random RPM's, but absolutley ALWAYS does it when the engine is under a load. For example: it's a manual, so when im in first gear, go to about 9-10 mph, shift into 2nd gear, disengage the clutch and give it some throttle, its a pretty loud ping/knock that will last approximately 1 full second until torque has developed and there's no longer a stressful load on the engine. However, at any random time, no matter what gear or MPH, it will ping or knock. The only time it doesn't do this is when it is VERY cold (I live in PA), or when i am at highway speeds. There are absolutley no CEL's. The knock sensor isnt even picking it up. The motor is completely stock. 51,000 miles. I have OCD and change the oil every 3000 miles with AMSOIL 0-20 and a WIX filter. I always let this motor warm up to 120+ degrees before driving, and baby it until it reaches fully operating temperature (coolant and oil). Oil pressure is constant a 31 PSI. I have also did a smoke test to check for any vacuum leaks and could not find any. It also does not ping/knock when revved up in neutral or at idle.

I thought for the longest time that it was a loose nut/bolt rattling around the frame or engine bay, and i searched for a "rattle" (which is the only way to describe the sound if i didn't find out later it was in fact engine ping/knock), and i couldn't find shit. i looked under that engine and inside the frame holes and checked every single nut and bolt that was exposed enough for me to touch and made sure they were at the least finger tight and not moving around. i thought maybe the vibration in that specific RPM/throttle % zone would cause a vibration throughout the chassis/engine and it was just rattling a rock or nut or bolt or something.

Fast forward to July 4. The gas station chain (Sheetz) was selling gas, in any octane, for $1.776. I was 25 miles to empty, so i filled with 93 octane. i drove home (~2 miles) and motor was still pinging. Parked it and haven't drove it...

Until yesterday. Not only did I notice NO knocking/pinging whatsoever, the entire thing runs so much smoother. No matter what load i put on the engine, how low my rpm's were, how high the gear was, it NEVER knocked or pinged one time, and it was 91 degrees here.

Heres my questions:
1 - How do i fix this? I have an aftermarket warranty, but would they replace the engine or re-tune this?
2 - Before posting this I've read threads and people say this is common? and that FCA/Jeep said to just run 91+ and keep it above 2k RPM's? is this true? this vehicle is not REQUIRED to run 91+ octane, and i would imagine there would be a recall for an engine re-tune considering this cant be good for the motor?

I can try to post video of this noise, but my doors/top is off at the moment. I can link videos extremely similar to the noise it makes that i have found on youtube if that helps.

That engine has a compression ratio of 10.6:1 and should burn 87-89 with no issue. If it knocks on 93 Octane then something is really wrong. 93 Octane will support about a 12:1 CR and not many cars run that kind of CR.

What does you temp gage show under normal driving?


Several years ago I put a Supercharger on my straight 6 2003 engine an it had a 8:1 Cr and I was running a 7 lb boost. Things worked great until a Hottie showed up her name was Summer and knocking got so bad I could only drive on city streets at 40 mph or below.

Being the engineer I am I was determined to fix the problem and I did. I installed hood vents to reduce engine bay temps. Helped but still could not hit the freeways or interstate speeds.

The I added TRUE CAI Cold Air Intake and problem solved. Back story: A friend bought a barn Jeep, CJ 5. Jeep was all OEM and used on a farm for only a few years and put in the barn. Rotted out for sure but other than that it was a 10. I helped him get it home on his trailer.

I opened the hood and what did I see an OEM CAI. Flext tube from Air cleaner to behind the Headlight bucket..

So I fabbed one up, ran it from my SC intake to my headlight bucket and knock knock left the building and I drove it like that for another 80k miles, never knocked again and I was 87-89 octane.

Take Away: Your engine may be getting too hot due to a thermostat issue????

You have Pre-Detnation aka Pre-Det. This would indicate an issue with timing, some where some how your timing has got off. Not sure how many miles you have on your Jeep but you may have a Timing Chain or Belt that has slipped and altered the timing. I say most likely this is your issue...

 

[Gorilla57]

That engine has a compression ratio of 10.6:1 and should burn 87-89 with no issue. If it knocks on 93 Octane then something is really wrong. 93 Octane will support about a 12:1 CR and not many cars run that kind of CR.

What does you temp gage show under normal driving?


Several years ago I put a Supercharger on my straight 6 2003 engine an it had a 8:1 Cr and I was running a 7 lb boost. Things worked great until a Hottie showed up her name was Summer and knocking got so bad I could only drive on city streets at 40 mph or below.

Being the engineer I am I was determined to fix the problem and I did. I installed hood vents to reduce engine bay temps. Helped but still could not hit the freeways or interstate speeds.

The I added TRUE CAI Cold Air Intake and problem solved. Back story: A friend bought a barn Jeep, CJ 5. Jeep was all OEM and used on a farm for only a few years and put in the barn. Rotted out for sure but other than that it was a 10. I helped him get it home on his trailer.

I opened the hood and what did I see an OEM CAI. Flext tube from Air cleaner to behind the Headlight bucket..

So I fabbed one up, ran it from my SC intake to my headlight bucket and knock knock left the building and I drove it like that for another 80k miles, never knocked again and I was 87-89 octane.

Take Away: Your engine may be getting too hot due to a thermostat issue????

You have Pre-Detnation aka Pre-Det. This would indicate an issue with timing, some where some how your timing has got off. Not sure how many miles you have on your Jeep but you may have a Timing Chain or Belt that has slipped and altered the timing. I say most likely this is your issue...

Actually, the old 3.6L had a compression ratio of 10.2:1 and the new 3.6 is 11.3:1

 

[Old Jeeper]

Actually, the old 3.6L had a compression ratio of 10.2:1 and the new 3.6 is 11.3:1

I looked it up for a 2018, Jeep Wrangler V6 3.6 and it said 10.6...THAT said changing CRs is done all the time to meet mpg and hp and EPA standards etc, nothing unusual...that why I looked it up!

 

[NWJeepr]

The timing is variable and is controlled by the computer. FCA/Stellantis seems to have all 3.6's programmed to advance the timing as much as possible given the conditions, maybe just a little too much for certain conditions. When I had mine, this is what a dealer tech told me, and he also said the frequency and volume of the pinging was harmless. Using higher octane in warmer weather seemed to be an anecdotal cure for the noise. However, I never felt more power or got better MPG with higher octane.

 

[flyer92]

I recently discussed this same issue in a related thread, although my JL's pinging only seems to manifest for half a second between 20 and 40 mph and is very faint. In that thread, I was reminded of the excerpt below from the owner's manual. Granted, the terms "light knocking" and "heavy knocking" are very subjective, but just something to consider. Hope you get this figured out and please keep us posted.

 

[JT1]

I looked it up for a 2018, Jeep Wrangler V6 3.6 and it said 10.6...THAT said changing CRs is done all the time to meet mpg and hp and EPA standards etc, nothing unusual...that why I looked it up!

There were 2 models of wranglers (JK and JL) sold in 2018. The versions in the JL are 11.3:1

 

[Old Jeeper]

There were 2 models of wranglers (JK and JL) sold in 2018. The versions in the JL are 11.3:1

It was the JK...

 

[JT1]

It was the JK...

Jeeps fault for not calling the JL a 2019.. ANY data for 2018 is liable to be wrong.

 

[flyer92]

Interestingly, I own a 2016 GC with the previous generation of the 3.6L Pentastar and have never experienced knocking/pinging under any conditions, nor any of the other issues identified in the forums. I suspect this is caused by Stellantis trying to better reduce emissions and comply with CAFE standards in an existing engine without having to develop an entirely new one. From their perspective, this is a good business decision because it saves money (for the short term anyway). From our perspective, we're left with an engine that's as pingy (in many cases) as my dad's 1971 Dodge Dart. Can't believe we're still dealing with these same issues more than 50 years later.

 

[oldcjguy]

The knock sensor isnt even picking it up. The motor is completely stock. 51,000 miles.

This statement concerns me. Are you assuming it's not picking it up or you've monitored the pid and it's not picking it up? A knock sensor should be picking up detonation pinging way before your ear can. If you're hearing it and it's not being picked up by the sensor, either the knock sensors are bad or it's not pinging, but some other rattle. I understand it stopped after the 93 octane. Could that be because the engine is running smoother with 93 and not causing the rattle?

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