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Discussion Starter · #1 ·
Hey everyone,
I have a 2015 SRT @150k miles currently. I'm experiencing audible pinging (but no hesitation felt like a misfire) under partial throttle and when the engine is fully warmed. This doesn't occur under WOT. This mostly occurs when coasting and stepping on the gas. I think this is where the vct/vvt is in its most advanced phase.

The heads and valves were recently serviced at a machine shop when replaced all valve springs, so it's unlikely to be carbon build up.

Any ideas on what might be the causes?

Also, thoughts on going 1 step colder spark plugs? the car has CAI, 92mm throttle body, and a tune.

Thanks!
 

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If the noise is more like a tinkling sound then in the good old days it would be a loose piston pin bushing. From your description of light load and fully warmed up to produce the noise that would be my opinion. A scan tool might show a bad knock sensor but I doubt it.
 

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Discussion Starter · #7 ·
If the noise is more like a tinkling sound then in the good old days it would be a loose piston pin bushing. From your description of light load and fully warmed up to produce the noise that would be my opinion. A scan tool might show a bad knock sensor but I doubt it.
Just had the car on a dyno, no crazy knock sensor readings observed. My tuner was leaning more towards poor gasoline or a spark plug being defective since ignition timing on light load is at its most advanced, around 27 degrees if I remember correctly.
Just ordered colder ngk plugs and will report back after testing.
 

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Just had the car on a dyno, no crazy knock sensor readings observed. My tuner was leaning more towards poor gasoline or a spark plug being defective since ignition timing on light load is at its most advanced, around 27 degrees if I remember correctly.
Just ordered colder ngk plugs and will report back after testing.
I think NGK is the OE spark plug. For sure they are the best. I'd be interested to hear if a colder heat range eliminates the noise.
 

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2014 Jeep SRT8. Stock. Used buy in 2020 @61,000 mi. Brilliant black crystal pearl
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I’d stay simple and start with better fuel and plugs. The way this operates with two plugs it gives false impressions that it’s doing ok because there’s two. I have been having issues on my stock setup coming back to plugs. Couldn’t hurt. Except the pocket…..
 

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Discussion Starter · #12 ·
Liquid Automotive lighting Fluid Drinkware Gas

Household hardware Tin Gas Cylinder Auto part

Update: even though the old plugs were not in a good shape, the new colder plugs did not prevent pinging!

Also worth mentioning there were no issues with the coils reaching down enough for the plugs even though there's a height difference.
 

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When the throttle is closed, as in deceleration, or only slightly open, during transition to cruise, the cylinder pressure is very low, even on the firing stroke. Air is restricted, as is fuel, and the static compression ratio is meaningless as there is insufficient air to build any amount of pressure- just enough to start combustion if the throttle is opened slightly. If the throttle is closed the fuel is shut off and no combustion occurs. So if the noise is on deceleration or slight part throttle, it's probably mechanical in nature rather than combustion. I'm still leaning towards a pin bushing. The appearance of the used plug certainly shows a great deal of wear and use, but also shows the heat range is correct.
 

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2013 Wk2 Srt8
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From what I can see on the first photo of the plug ignition timing looks to a to advanced, this will cause pinging as the stock of the piston is to close to the top of the stroke or you have some hot points causing pre-combustion the combustion chamber in the heads is very corse from sand used in the cast poring although the shop where you just had the work done I assume would have or should have polished or smoothed out the coarse surface texture
 

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Discussion Starter · #15 ·
If it's a pin bushing that requires pretty much a complete tear down. I'll just data-log to see what exactly is happening. Also might try an octane booster hopefully to confirm whether it's the pin bushing or ignition-related.
 

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2014 Jeep SRT8. Stock. Used buy in 2020 @61,000 mi. Brilliant black crystal pearl
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Honestly man octane booster is just alcohol. You need actual fuel. Look at a motorcycle shop they should have a 5 gallon can of VP or something along those lines. Octane booster is a gimmick for real. You need real high octane fuel. Even a small airport should have pumps you can get to that have real high octane. It’s a pain in the ass but nothing you dump in the tank like an additive will do anything at all for you. They wouldn’t even make high octane they’d just sell you a bottle of that crap if it worked that good. Just going from experience man I’d get some real stuff
 

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2014 Jeep SRT8. Stock. Used buy in 2020 @61,000 mi. Brilliant black crystal pearl
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I’d still try legit fuel man. I’m not sure how much ethanol is in your fuel where your at. Over here in the states the max was upped to 15% and I noticed my R1 was pinging the other day after fresh 93. It only does that with crappy gas like the 87 octane my friend put in after borrowing once and then no more. It was 80°F out and I was in traffic and the engine was hot so it was definitely the right conditions for some detonation on the low end for me. I know I’m rambling but I guess what I’m getting at is I’m not sure the integrity of fuel at the pump right now is trustworthy. Anywhere. Just try to keep that in mind. Maybe a bad knock sensor? Failing injector? I’m still leaning toward fuel. That’s usually the cause in my experience. Let us know what you find!!! I’m curious if my fuel theory has any outcome. I’m going to hafta cut my fillups with vp now is my try.
 

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Who does your tuning? Do you still have your stock TB? If so throw that on and see if you still get the ping. Seen lots of issues and trouble tuning larger TB's over the years with funny behavior. With those few of mods there should be no reason to go one step colder on plugs
 

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Discussion Starter · #20 · (Edited)
I’d still try legit fuel man. I’m not sure how much ethanol is in your fuel where your at. Over here in the states the max was upped to 15% and I noticed my R1 was pinging the other day after fresh 93. It only does that with crappy gas like the 87 octane my friend put in after borrowing once and then no more. It was 80°F out and I was in traffic and the engine was hot so it was definitely the right conditions for some detonation on the low end for me. I know I’m rambling but I guess what I’m getting at is I’m not sure the integrity of fuel at the pump right now is trustworthy. Anywhere. Just try to keep that in mind. Maybe a bad knock sensor? Failing injector? I’m still leaning toward fuel. That’s usually the cause in my experience. Let us know what you find!!! I’m curious if my fuel theory has any outcome. I’m going to hafta cut my fillups with vp now is my try.
No ethanol over here in Saudi Arabia. The highest pump fuel available is 95 RON, equivalent to 91 octane in the US.
I will definitely have the injectors checked next since my milage is high @ 150k miles.
 
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