Am I the only one having spark knock issues?

[Jeeperjamie]

You must have just had some bad gas. Knock protection is the fundamental reason to go for higher octane. More timing, more likely to have early detonation, which the higher octane protects against. OEM's usually don't tell you what octane to run, they give you a minimum. In the Gladiator manual they just tell you that higher octane doesn't help you.

Another way to talk about it is with air temperature and/or altitude. Early detonation is more likely to happen with warmer air (less oxygen). Higher octane increases the temperature at which early detonation can occur, effectively lowering the chances of it happening at the same air temperature. Higher altitude works the same way as warmer air (less oxygen) which is why in places like Colorado you'll see 85 octane as the minimum octane sold vs 87. The cars can handle the lower octane because they're less likely to knock since their air has a lower oxygen content. All of this is why I typically will run mid grade (typically the 88 octane from Sheetz) fuel when it's really hot out and then I move back to 87 when it cools down.

I promise you it wasn't bad gas. I kept putting the higher octane in for a couple months with it knocking before I took it in to my buddies shop, who looked it over and found nothing wrong with it. He then asked if I had changed anything on it or been driving it differently, and I told him I had been running the higher octane gas and he suggested running what the manual says. He told me to run 87 octane it in for next few fill ups and see if it made a difference, well it did and the knocking went away. Like I said it knocked for two months, roughly 8,000 miles worth of driving and it took about 800 miles of regular gas to get it back to being quiet. I'm 100% positive it wasn't bad gas.

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[kelkolb]

I promise you it wasn't bad gas. I kept putting the higher octane in for a couple months with it knocking before I took it in to my buddies shop, who looked it over and found nothing wrong with it. He then asked if I had changed anything on it or been driving it differently, and I told him I had been running the higher octane gas and he suggested running what the manual says. He told me to run 87 octane it in for next few fill ups and see if it made a difference, well it did and the knocking went away. Like I said it knocked for two months, roughly 8,000 miles worth of driving and it took about 800 miles of regular gas to get it back to being quiet. I'm 100% positive it wasn't bad gas.

That's strange. That goes against all knowledge about engine knocking related to octane.

 

[Jeeperjamie]

That's strange. That goes against all knowledge about engine knocking related to octane.

Didn't make sense to me either but that's what happened. I always thought that the higher Octane helped with engine ping and knocking but that time it was the opposite. I was able to run the higher octane without knock after I used the flashpaqs, but if I'm honest I preferred running the 87 octane setting over any of them. It just felt like the jeep ran better on that setting.

I do know you don't want go opposite and run lower octane in a vehicle that requires higher octane. My son was driving our last bmw 328i and was running 87 in it because he didn't realize it required 93 and it ended up making it rough idle and I had replace two coil packs.

 

[Benbean66]

Wow... I was just thinking about how to ask this very same question, when I stumbled upon this thread. I have a slight, but noticable amount of pre-ignition mainly at low to mid rpm and while feather footing the throttle. Tried a tank of 89 to see if it changed, and it did not. Has there been any resolution to this issue, or should it be chalked up to "It's a Jeep Thing?"

 

[Logan94605]

I was noticing the smallest of like little weird sound at initial acceleration... nothing like knock I hear from YouTube videos, and I really have no way to describe it. Only at low rpm as it starts to accelerate initially and then gone. Is that what you all are talking about?

Hmmm I started getting the same thing a couple days ago. I'm around 2000 miles in and it just started a slight ping under load like on a hill or something and in a low gear. I'm wondering if it might be a winter fuel change?

 

[DanW]

I'm not sure how accurate it is to say that higher octane adds knock protection because I ran higher octane in my JKU and it began to knock. That's after about 10-12 fill-up in the beginning. I ended up switching back to Regular and after a few cycle and fill ups I was able to make the knocking noise go away. After buying the flashpaq tuner I tried again and didn't have a issue. Worth noting also that I had similar issues in a BMW 328I as well. There a reason they tell you what Type of gas to run. But I will agree that tuning them will get the best bang if you decide to run higher octane fuel. I think there is a huge misconception behind the benefits of running higher octane gas and fully synthetic oil in some cases. If I can find it I'll post the video of the study done in using lower octane in higher octane vehicles and the opposite, it's pretty interesting the results.

Then you had a problem. Octane rating is simply a measure of a fuel's resistance to predetonation, which is the cause of pinging/knocking. I'd get that looked at, pronto. The Pentastar should not be pinging or knocking on 87 octane, at all.

I've got the same engine as you, and at 37k miles, it experiences none of that. In fact, no Pentastar I've ever driven has done it. My 08 JK's 3.8 will do it, but only when there is carbon build up.

The first thing I'd do is run a tank or 2 of Shell V-Power or Chevron supreme with Techron through it. Then, start running Shell 87 for several tankfuls. At a minimum, I'd only run Top Tier certified fuel. Carbon buildup is probably the most common cause of pinging. Some engines described in this thread are pretty new to be experiecing it, even though it doesn't take many tanks of lower quality fuel to cause buildup. I'd also make sure the oil you are running is API SN+ or SP rated, along with Dexos 1 Gen 2. They are designed to prevent low speed pre-ignition in direct injected engines. If the pinging is caused by carbon buildup, then it might help.

 

[DanW]

Didn't make sense to me either but that's what happened. I always thought that the higher Octane helped with engine ping and knocking but that time it was the opposite. I was able to run the higher octane without knock after I used the flashpaqs, but if I'm honest I preferred running the 87 octane setting over any of them. It just felt like the jeep ran better on that setting.

I do know you don't want go opposite and run lower octane in a vehicle that requires higher octane. My son was driving our last bmw 328i and was running 87 in it because he didn't realize it required 93 and it ended up making it rough idle and I had replace two coil packs.

I'd switch fuel suppliers. That makes no sense at all. Have you tested the octane of the fuel? Have you run high octane fuel from another gas station? What brands of gas are near you?

 

[Jeeperjamie]

Then you had a problem. Octane rating is simply a measure of a fuel's resistance to predetonation, which is the cause of pinging/knocking. I'd get that looked at, pronto. The Pentastar should not be pinging or knocking on 87 octane, at all.

I've got the same engine as you, and at 37k miles, it experiences none of that. In fact, no Pentastar I've ever driven has done it. My 08 JK's 3.8 will do it, but only when there is carbon build up.

The first thing I'd do is run a tank or 2 of Shell V-Power or Chevron supreme with Techron through it. Then, start running Shell 87 for several tankfuls. At a minimum, I'd only run Top Tier certified fuel. Carbon buildup is probably the most common cause of pinging. Some engines described in this thread are pretty new to be experiecing it, even though it doesn't take many tanks of lower quality fuel to cause buildup. I'd also make sure the oil you are running is API SN+ or SP rated, along with Dexos 1 Gen 2. They are designed to prevent low speed pre-ignition in direct injected engines. If the pinging is caused by carbon buildup, then it might help.

For one it wasn't a penastar engine it was a JKU with the 3.8 not the JT that I had the issue in.

 

[Jeeperjamie]

I'd switch fuel suppliers. That makes no sense at all. Have you tested the octane of the fuel? Have you run high octane fuel from another gas station? What brands of gas are near you?

Shell and BP and Chevron are the only ones I use, mainly BP and that's more than one station. I have never had a issue before from any of them out of any vehicle.

 

[DanW]

For one it wasn't a penastar engine it was a JKU with the 3.8 not the JT that I had the issue in.

Ok, then knocking pinging makes more sense, as that engine is more prone to it, partly due to being more prone to carbon buildup. Mine has stopped doing it since I've been running SN+ oil in it and also since Shell updated their additive pack in their regular fuels. But before that I'd get pinging after 3k to 5k miles. I'd run a tank of V-Power and do a few Italian tune-ups and it would clear it out for another few thousand miles. But higher octane ALWAYS stopped it. Even 89. But again, I ran Shell gas probably 95% of the time.

What spark plugs are you running? I once ran NGK's top of the line irridium plugs and the think knocked like crazy. I went back to the OEM spec Champion double platinum plugs. I gap them myself, at .050. An old Chrysler tech told me that engine simply doesn't do well with any other plug than the OEM Champion. I was shocked at how quickly and badly the NGK's started to ping. I also change the Champion plugs every 40-50k, as the gaps will start to open. They can easily go 100k, but I'd still pull them and re-gap at 50k.

If you pull the plugs, post pictures. Their color, gap, and condition might give us an idea of what is happening.

 

[Jeeperjamie]

Ok, then knocking pinging makes more sense, as that engine is more prone to it, partly due to being more prone to carbon buildup. Mine has stopped doing it since I've been running SN+ oil in it and also since Shell updated their additive pack in their regular fuels. But before that I'd get pinging after 3k to 5k miles. I'd run a tank of V-Power and do a few Italian tune-ups and it would clear it out for another few thousand miles. But higher octane ALWAYS stopped it. Even 89. But again, I ran Shell gas probably 95% of the time.

What spark plugs are you running? I once ran NGK's top of the line irridium plugs and the think knocked like crazy. I went back to the OEM spec Champion double platinum plugs. I gap them myself, at .050. An old Chrysler tech told me that engine simply doesn't do well with any other plug than the OEM Champion. I was shocked at how quickly and badly the NGK's started to ping. I also change the Champion plugs every 40-50k, as the gaps will start to open. They can easily go 100k, but I'd still pull them and re-gap at 50k.

If you pull the plugs, post pictures. Their color, gap, and condition might give us an idea of what is happening.

I always run the autolites, never had a issue out if them in any vehicle I use them in. I haven't changed them in the JT yet. In the JKU the pinging stopped after I quit running high octane and went back to 87, I always ran 87 octane most of the time and 10w30 mobile 1 oil and changed it every 3,000 miles. Autolites spark plugs as well

 

[DanW]

I always run the autolites, never had a issue out if them in any vehicle I use them in. I haven't changed them in the JT yet. In the JKU the pinging stopped after I quit running high octane and went back to 87, I always ran 87 octane most of the time and 10w30 mobile 1 oil and changed it every 3,000 miles. Autolites spark plugs as well

They are great, but I'd bet you are having an issue with them in this engine. older Chrysler engines are generally notorious for not running well on non-OEM plugs. Get the OEM plugs, gap them properly, and you stand a very good chance of curing the problem. The NGK's I ran were their top of the line. They pinged TERRIBLY after only a few hundred miles and they did it even on 93 octane, which I've never seen before. It'd be well worth a try and would set you back about 36 bucks. I've lived with that 3.8 for 145k miles. My brother had one in a mini van. Same deal. He had his for over 200k. Ran better on Champions. They are part number 7440. Ask a tech at a Jeep dealer who knows this engine. They'll tell you to go with the Champions. It is what the engine was designed and tested on.

I'd do this before messing with gas, oil, or anything else. $36 is a small price to pay for even a chance to rid your engine of that issue.

If you get no pinging with 87 octane, then you are fine. Just stick with that. But this engine IS picky.

 

[Jeeperjamie]

They are great, but I'd bet you are having an issue with them in this engine. older Chrysler engines are generally notorious for not running well on non-OEM plugs. Get the OEM plugs, gap them properly, and you stand a very good chance of curing the problem. The NGK's I ran were their top of the line. They pinged TERRIBLY after only a few hundred miles and they did it even on 93 octane, which I've never seen before. It'd be well worth a try and would set you back about 36 bucks. I've lived with that 3.8 for 145k miles. My brother had one in a mini van. Same deal. He had his for over 200k. Ran better on Champions. They are part number 7440. Ask a tech at a Jeep dealer who knows this engine. They'll tell you to go with the Champions. It is what the engine was designed and tested on.

I'd do this before messing with gas, oil, or anything else. $36 is a small price to pay for even a chance to rid your engine of that issue.

Yeah, I'm not having a issue in my JT and I planned on running champion in it when the time came. Had 132,000 miles on the JKU when I sold it and it was running great. Sold it to the dealership for $11,000 when I was buying the JT.

 

[ShadowsPapa]

A healthy Pentastar shouldn't be knocking or pinging on regular 87 gas. I'd take it in and try and get them to do something about it. Also, I'd run a newer SP GF6 oil.

What's oil certifications got to do with pinging from detonation?

 

[ShadowsPapa]

Wow... I was just thinking about how to ask this very same question, when I stumbled upon this thread. I have a slight, but noticable amount of pre-ignition mainly at low to mid rpm and while feather footing the throttle. Tried a tank of 89 to see if it changed, and it did not. Has there been any resolution to this issue, or should it be chalked up to "It's a Jeep Thing?"

Whoa - pre-ignition is ignition BEFORE the spark.
Detonation is a second flame front that happens AFTER the spark.
Octane resists self-ignition - PERIOD.
Detonation is caused when the normal progressing flame front forces unburned mix "into a corner" and raises the pressure and thus temperature to the point it self-ignites. Then you have a second flame front advancing and the ping is the sonic boom caused by the collision.

Higher octane fuel has longer chains that resist self-ignition.

PRE-IGNITION is a TOTALLY different animal and is caused by HOT SPOTS - such as the wrong heat range spark plug, carbon build-up, sharp edges on valves after a crappy valve job and so on.

Let's not get the two - detonation and pre-ignition - mixed up or intertwined. They are two distinct things.

Also - spark plugs have ZERO to do with detonation. That's because detonation is a problem with a SECOND flame front, AFTER the plug fires. Octane and/or timing deal with that.

Spark plugs CAN cause preignition if they run too hot. Most of the issues with spark plugs isn't the quality of the plug, it's how hot it runs, how it cools, length and so on.

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