Rattle from engine when accelerating (sounds like keys)

[ShadowsPapa]

The pre-ignition happens on these engines because the VVT is tuned not in sync with the throttle. There is a transition spot were the valves are closed and the throttle has let in to much air and it causes a dynamic high compression event like the video. It goes away once the valves get caught up. I heard this numerous times when tuning my VVt

You still have the issue caused by heat and compression (and heat of compression).
Air has mass. Mass has properties like inertia.
Scavenging exhaust systems coupled with the right cam (talking legacy performance builds) and the right intake can raise your dynamic compression. Static compression is the ratio you get when you compare the volume of uncompressed gases to the volume of the same gases compressed. Thus, the 11.3 for example. But engines are sometimes more than 100% efficient. You need to know your engine's pumping efficiency when choosing a carburetor size.
So you have that engine pushing out exhaust gases - exhaust valve is open, piston coming up, just before piston hits the top, exhaust valve still open a bit, the intake opens. Now you have valve overlap. The exiting exhaust creates a siphon effect and starts pulling the fresh air in (in the case of my car, fuel/air mix) so the mix is starting to come in when the piston hasn't quite started the journey back down. You already have more than 100% of the air in there than what it would have normally drawn with no scavenging or overlap.
Piston almost down, intake still open, you have a nice column of air coming in - that that column is end to end (on a carbureted car) air horn to top of the piston. It's a single mass of air moving in. Piston hits bottom, intake STILL open just a bit, air still rushing in, now you have more than atmospheric pressure in the chamber and the piston hasn't really started compressing it yet. Valve closes, ideally just at the time the piston has enough movement to start pushing air back out. So with the right situation, you have OVER 11.3 dynamic compression ratio.
That's why you tune the exhaust system to work in conjunction with your cam and your intake system - perhaps a cross ram, where you have increased the length of the column of air rushing in.
I had detonation problems with my 70 390 (I found later part of it was the old radiator was partially plugged not allowing coolant flow) anyway, I put on different heads with slightly larger chambers, pistons designed to increase quench area quite a bit, measured everything to get as close a quench number as I could, picked out a nice mild cam - however, that cam had some radical ramps on it. The lift wasn't that much higher than stock, duration not that much longer, but the ramps were fast ramps, opened the valves fast, then slammed them shut fast.
In the end after consulting with some race guys we determined that while I did everything right reducing my compression ratio - I did decrease the static compression ratio, I INCREASED my dynamic compression ratio greatly - "free flow" exhaust manifolds, the cam, other factors, now I was running more air in during intake than I was before even though the head chamber area was larger.

So I was doing what was happening with some of these engines apparently - causing more air to go in, raising the dynamic compression ratio.
With a stock cam my other changes would have been fine. Even a different mild cam - a bit more lift, a tad more duration, but mine left the door open wider for a longer period.

With VVT (and VVL) you are shifting the torque up and down the RPM range, and changing the dynamic compression.
If things aren't just right - it's like David described.

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[Onebigyoshi]

You still have the issue caused by heat and compression (and heat of compression).
Air has mass. Mass has properties like inertia.
Scavenging exhaust systems coupled with the right cam (talking legacy performance builds) and the right intake can raise your dynamic compression. Static compression is the ratio you get when you compare the volume of uncompressed gases to the volume of the same gases compressed. Thus, the 11.3 for example. But engines are sometimes more than 100% efficient. You need to know your engine's pumping efficiency when choosing a carburetor size.
So you have that engine pushing out exhaust gases - exhaust valve is open, piston coming up, just before piston hits the top, exhaust valve still open a bit, the intake opens. Now you have valve overlap. The exiting exhaust creates a siphon effect and starts pulling the fresh air in (in the case of my car, fuel/air mix) so the mix is starting to come in when the piston hasn't quite started the journey back down. You already have more than 100% of the air in there than what it would have normally drawn with no scavenging or overlap.
Piston almost down, intake still open, you have a nice column of air coming in - that that column is end to end (on a carbureted car) air horn to top of the piston. It's a single mass of air moving in. Piston hits bottom, intake STILL open just a bit, air still rushing in, now you have more than atmospheric pressure in the chamber and the piston hasn't really started compressing it yet. Valve closes, ideally just at the time the piston has enough movement to start pushing air back out. So with the right situation, you have OVER 11.3 dynamic compression ratio.
That's why you tune the exhaust system to work in conjunction with your cam and your intake system - perhaps a cross ram, where you have increased the length of the column of air rushing in.
I had detonation problems with my 70 390 (I found later part of it was the old radiator was partially plugged not allowing coolant flow) anyway, I put on different heads with slightly larger chambers, pistons designed to increase quench area quite a bit, measured everything to get as close a quench number as I could, picked out a nice mild cam - however, that cam had some radical ramps on it. The lift wasn't that much higher than stock, duration not that much longer, but the ramps were fast ramps, opened the valves fast, then slammed them shut fast.
In the end after consulting with some race guys we determined that while I did everything right reducing my compression ratio - I did decrease the static compression ratio, I INCREASED my dynamic compression ratio greatly - "free flow" exhaust manifolds, the cam, other factors, now I was running more air in during intake than I was before even though the head chamber area was larger.

So I was doing what was happening with some of these engines apparently - causing more air to go in, raising the dynamic compression ratio.
With a stock cam my other changes would have been fine. Even a different mild cam - a bit more lift, a tad more duration, but mine left the door open wider for a longer period.

With VVT (and VVL) you are shifting the torque up and down the RPM range, and changing the dynamic compression.
If things aren't just right - it's like David described.

So I have the exact same noise as @Gladiator847 and the video he linked and I also have the manual transmission. Only happens in second and third gear when accelerating hard right after 3k rpm and stops around 3.5 ~ 4k rpm. Now it doesn't really happen anymore or if it does it's really faint not as loud as it used to be. Could the issue still be related to what you're talking about or maybe something else?

 

[NateO]

I just posted on this a few mins ago.
Same type of issues. Any fixes yet?
Post below:
I have a 2020 Jeep Gladiator Rubicon, while driving around @ a low speed my truck will shift into 3rd at 1400rpm and will start this chattering noise kinda like spark knocking. I've taken it to the dealer and they claim they cant find any thing wrong.
Also I keep getting a check eng light. Mis-fire the dealer replaced my coils and still it happens.
One more issue. not that I like it but my Start/stop system keep disabling because there is an issue with it. Took it to the dealer they gave me this passive reply of; Well if you do a lot of in town driving the system gets drained and will cause this warning. I'm calling BS!!!
The truck just turn 17k. Any one have the same issues?

 

[ShadowsPapa]

I just posted on this a few mins ago.
Same type of issues. Any fixes yet?
Post below:
I have a 2020 Jeep Gladiator Rubicon, while driving around @ a low speed my truck will shift into 3rd at 1400rpm and will start this chattering noise kinda like spark knocking. I've taken it to the dealer and they claim they cant find any thing wrong.
Also I keep getting a check eng light. Mis-fire the dealer replaced my coils and still it happens.
One more issue. not that I like it but my Start/stop system keep disabling because there is an issue with it. Took it to the dealer they gave me this passive reply of; Well if you do a lot of in town driving the system gets drained and will cause this warning. I'm calling BS!!!
The truck just turn 17k. Any one have the same issues?

System gets drained? Most of my driving is rural and town driving, errands, etc. Granted if it SITS for a day or two I have a not ready, battery charging message on the cluster page for the ESS. But you can check that yourself- check the cluster display where it shows the ESS status. If it says not ready battery charging or something like that, you either have a battery issue or it's not yet charged up due to sitting and frequent stops. You could put a small charger on the batteries over night then drive it and check for that cluster message again. If it's not able to function, it will normally tell you why.

1400 rpm is an area I'd expect a "ping" if there was going to be one - it shouldn't do it, but if it's going to, lower RPM is the most likely area.
Minor light ping isn't normally a big deal, not for most engines, but prolonged and/or loud, it's not good. That dealer sounds like they aren't interested in trying - if they hear the ping, or you can make it happen for them - then they should be forced to dig until they find something, even contacting Jeep - perhaps star team.

The misfire issue - if you have a program like AlfaOBD and a bluetooth OBDII device, maybe you can catch it in the act, record the codes and other information and at least show if it's an ignition misfire or something else.

This is an example of what I took to our local dealer for my wife' s 3.6 when it was misfiring badly enough the thing jerked as you drove it - it's several pages long in full, but this give an idea. They saw this and had no choice but to follow through - it took them hours to figure out but they found an obscure TSB related to misfires in 2021 3.6 in the Grand Cherokee - spark plugs.
Note where it says "Error warning lamp not requested" - the MIL never came on! So I knew I had to capture it actually happening to prove it. Good thing, too, as while I drove it to the dealership, by the time I got there the misfire had stopped and the engine smoothed out.

2021/01/04 11:56:32.011: Faults found: P0303
2021/01/04 11:56:35.970: Faults found: P0303
Error code: P0303
Cylinder 3 ignition failures
Test not complete
Error intermittent
Error warning lamp not requested
CARB Freeze Frame:
___________________
Fault code: P0303
PCM Mileage since MIL On: 0.00 miles
PCM Odometer: 950.27 miles
Open Loop - Bank 1: No
Closed Loop - Bank 1: Yes
Open Loop due to Driving Conditions - Bank 1: No
Open Loop with DTC - Bank 1: No
Closed Loop with DTC - Bank 1: No
Open Loop - Bank 2: No
Closed Loop - Bank 2: No
Open Loop due to Driving Conditions - Bank 2: No
Open Loop with DTC - Bank 2: No
Closed Loop with DTC - Bank 2: No
Engine load: 30.20 %
Freeze Frame Engine Coolant Temp: 66.00 Deg.C
Intake Air Temperature: 215.00 Deg.C
Ambient Air Temperature: 12.00 Deg.C
Short Term Fuel Trim - Bank 1: 12.49 %
Long Term Fuel Trim - Bank 1: -3.13 %
Short Term Fuel Trim - Bank 2: 9.37 %
Long Term Fuel Trim - Bank 2: -7.04 %
MAP Voltage: 1.96 V
MAP: 46 kPa
Atmospheric pressure: 97 kPa
Engine RPM: 875.00 rpm
Vehicle speed: 0 MPH
Throttle Position Sensor 1 Percent: 12.94 %
Battery voltage: 14.58 V
Fuel level: 95.69 %
Purge Solenoid Current: 0.00 mA
Purge Duty Cycle: 0.00 %
Idle Air Control (IAC) Current: 0.00 mA
Idle Air Control (IAC) Duty Cycle: 0.00 %
EGR Flow: 0.00 g/s
Current Adaptive Cell ID: 24
Spark advance: -2.00 Deg
AC Clutch: Disengaged
EGR Gassed Flowing: No
Power Steering High Pressure: No
AC Switch: Off
PRNDL in Gear: No
Brake switch: Pressed
Low Ethanol PWR Enrich Flag: No
Low Ethanol Therm Management Flag: No
Ethanol Gas For Sure: No
Ethanol Mode: No
Ethanol - 0% Blend Direction: No
Ethanol - 85% Blend Direction: No
Ethanol - Open Loop Fuelling: No
Ethanol Fine Tune Complete Previous: No
Ethanol Fuel Volume Changed: No
Ethanol Low Fuel: No
Ethanol Trigger On Fuel Volume Fault: No
Ethanol Trigger During Learn: No
Ethanol Learn: Disabled
Ethanol Course Update Ready to Learn: No
Ethanol Course Update: Not completed
Ethanol Fine Tune: Not completed
Actual Torque: 0.84 Nm
Potential Torque: 78.16 Nm
Target throttle position: 2.56 V
Electronic Throttle Control (ETC) Motor Directional Duty Cycle: -20.67 %DC
Electronic Throttle Control (ETC) Motor Duty Cycle: 20.67 %DC
Throttle position sensor 1: 2.58 V
Throttle position sensor 2: 17.42 V
Accelerator pedal sensor 10.44 V
Accelerator pedal sensor 20.22 V
Accelerator pedal position: 0.00 %
Brake switch 1: Released
Brake switch 2: Released
H-Bridge Circuit: Enabled
Ignition Run/Start Switch: On
Throttle Flow Adaptive: 0.13 g/s
Throttle Flow Multiplicative Adaptive: 2.00
PHI Adaptation Value: 0.00
Calculated MAP: 46.59 kPa
Ethanol Percent: 0.00 %
Turbo Boost Timer: 0.00 ms
Throttle Inlet Pressure: 0.00 kPa
Throttle Inlet Pressure Voltage: 320.34 V
Turbo Airport Mass Flow: 3.45 g/s
Turbo PRatio: 1.00
Turbo Torque Count: 0
Turbo Speed: 65535 rpm
Turbo Wastegate Duty Cycle: 200.01 %DC
Time since Run/Start: 45 sec
___________________
First Service Freeze Frame:
___________________
Fault code: P0303
PCM Mileage since MIL On: 0.00 miles
PCM Odometer: 950.27 miles
Open Loop - Bank 1: No
Closed Loop - Bank 1: Yes
Open Loop due to Driving Conditions - Bank 1: No
Open Loop with DTC - Bank 1: No
Closed Loop with DTC - Bank 1: No
Open Loop - Bank 2: No
Closed Loop - Bank 2: No
Open Loop due to Driving Conditions - Bank 2: No
Open Loop with DTC - Bank 2: No
Closed Loop with DTC - Bank 2: No
Engine load: 30.20 %
Freeze Frame Engine Coolant Temp: 66.00 Deg.C
Intake Air Temperature: 215.00 Deg.C
Ambient Air Temperature: 12.00 Deg.C
Short Term Fuel Trim - Bank 1: 12.49 %
Long Term Fuel Trim - Bank 1: -3.13 %
Short Term Fuel Trim - Bank 2: 9.37 %
Long Term Fuel Trim - Bank 2: -7.04 %
MAP Voltage: 1.96 V
MAP: 46 kPa
Atmospheric pressure: 97 kPa
Engine RPM: 875.00 rpm
Vehicle speed: 0 MPH
Throttle Position Sensor 1 Percent: 12.94 %
Battery voltage: 14.58 V
Fuel level: 95.69 %
Purge Solenoid Current: 0.00 mA
Purge Duty Cycle: 0.00 %
Idle Air Control (IAC) Current: 0.00 mA
Idle Air Control (IAC) Duty Cycle: 0.00 %

 

[HeartwoodJT]

Add mine to the list. 8k miles, auto. Has been doing it all summer, could have been longer because I noticed it with the top off. Just switched from 87 to 91 oct and it seems to have gotten mostly better, but not gone. Only happens when lugging in low RPMs accelerating. I’m afraid to take it to the dealer because I’m afraid they will void my warranty d/t lift and tires.

 

[DAVECS1]

So checkout the throttle sensor voltage and your map. If the valves are doing what is expected from a low lift cam vacuum should be atleast 10kpa lower. The cam is phazed in a way it is restricting intake and pushing everything out the exhaust thus making the chamber closer to atmospheric and creating a low fuel high combustion potential. Which basically gives you unstable burn time.

 

[Higher_Ground]

I'm at just under 8k miles. I had noticed it intermittently but I've narrowed down to pretty much low speed driving (10-15 mph) in 3rd gear. I will try using 91 and see if it helps.

I mentioned before I have to drive over a lot of speed humps. They are signed for 15 mph on roads typically 25 mph. So I let off the accelerator, maybe brake lightly, and then accelerate again after I'm over the hump. Unless I'm really, really easy on the accelerator it starts to rattle/ping for about half of a second. It doesn't keep pinging and it's not loud - you need the top off and radio down to hear it.

It doesn't do it during normal driving or accelerating from stop lights.

There seem to be 3 steps involved to make it happen:
1) truck is moving around 10-15 mph with normal throttle
2) let off throttle entirely, truck decelerates ~5 mph (over speed hump)
3) hit the gas -> around 1/2 sec of pinging.

I have the Sport S, automatic transmission, 3.73 gears and larger tires (LT285/75r17) for what it's worth. Is this something that's going to destroy the engine long before I hit 100k or just increase wear?

 

[ShadowsPapa]

I've now seen several posts where ping could be expected because the engine is being forced into "lugging" - low RPM, heavy throttle, it's struggling.
My solution - lower gear, downshift, or give it enough "gas pedal" to force an automatic into downshift.
Keeping them in a high gear and giving throttle at RPMs under say, 1600 - that's asking for conditions to ping. That's called "lugging the engine" and it's not good. Heck, if I try to take a hill in 3rd gear in my car at 1400 RPM I can force it to ping it I try. So I downshift to 2nd and make the RPM climb out of that range.
Stay out of the mid-teens RPM-wise. Downshift, or give it more throttle and force a downshift.

 

[Hootbro]

................... - it took them hours to figure out but they found an obscure TSB related to misfires in 2021 3.6 in the Grand Cherokee - spark plugs.
.........

I assumed they changed the spark plugs and that fixed the problem?

Reason I ask is that have a random P0304 #4 misfire code that is pending but never posting the MIL. Found it when I was getting an occasional ESS not available lamp icon posting.

Only seems to happen on a 8 hour+ sitting cold start. Checked it with JScan I would have a misfire count on #4 of 30 to 50 something. Seems anything about a 50+ count will trip the pending P0304. Misfire count on #4 seems to smooth out within 10 seconds or so after starting and is fine for the rest of my drive. Subsequent hot starts and no issue.

I am pretty sure the #4 cylinder is on the drivers left bank and the intake covers the coil, plugs and injectors on that side. Otherwise, I would done some swaptronics on all three to see if it traveled.

Spark Plugs are a 100K mile change interval but seriously debating doing it shortly when I hit 30K miles. Just do not want to deal with the dealership bufoonery since a hard MIL code is not posting and the pending P0304 code resets after a couple ignition cycles to only happen again a week or two later.

 

[ShadowsPapa]

I assumed they changed the spark plugs and that fixed the problem?

Reason I ask is that have a random P0304 #4 misfire code that is pending but never posting the MIL. Found it when I was getting an occasional ESS not available lamp icon posting.

Only seems to happen on a 8 hour+ sitting cold start. Checked it with JScan I would have a misfire count on #4 of 30 to 50 something. Seems anything about a 50+ count will trip the pending P0304. Misfire count on #4 seems to smooth out within 10 seconds or so after starting and is fine for the rest of my drive. Subsequent hot starts and no issue.

I am pretty sure the #4 cylinder is on the drives left bank and the intake covers the coil, plugs and injectors on that side. Otherwise, I would done some swaptronics on all three to see if it traveled.

Spark Plugs are a 100K mile change interval but seriously debating doing it shortly when I hit 30K miles. Just do not want to deal with the dealership bufoonery since a hard MIL code is not posting and the pending P0304 code resets after a couple ignition cycles to only happen again a week or two later.

Yes, they changed the spark plugs (and where those are makes me glad I'm retired) and the thing has been perfect since.
Note that my diagnostics specifically said "ignition". I need to see if I can find a copy of that TSB to see just how it reads.
WEIRD, not even a thousand miles - and spark plug causing a misfire. I'd love to know the difference between what it came with and what they put in - same exact number? Same heat range?


2021/01/04 11:56:32.011: Faults found: P0303
2021/01/04 11:56:35.970: Faults found: P0303
Error code: P0303
Cylinder 3 ignition failures
Test not complete
Error intermittent
Error warning lamp not requested

 

[Hootbro]

Yes, they changed the spark plugs (and where those are makes me glad I'm retired) and the thing has been perfect since.
Note that my diagnostics specifically said "ignition". I need to see if I can find a copy of that TSB to see just how it reads.
WEIRD, not even a thousand miles - and spark plug causing a misfire. I'd love to know the difference between what it came with and what they put in - same exact number? Same heat range?


2021/01/04 11:56:32.011: Faults found: P0303
2021/01/04 11:56:35.970: Faults found: P0303
Error code: P0303
Cylinder 3 ignition failures
Test not complete
Error intermittent
Error warning lamp not requested

Attached is the 09-013-20 REV. A TSB for the Spark Plugs. It was a bitch to get as it was not on the interwebs anywhere. Had to go to Tech Authority and pull it up there. Does not seem to be assigned by VIN to anything I tried to input. They seem to really want this one buried.

What is interesting is they list other 2020-2021 models as being affected but only 2021 for the Gladiator and Wrangler. Then the build on and after and before info is contradictory. I think this has been an issue with bad crack spark plugs on the Gladiator from the get go of the 2020 model year even with the early 2019 build date models.

Seems the MOPAR OEM spark plugs are made by Champion and that would explain a lot with the crappy quality.

 

[flipmode]

Really appreciate this information @Hootbro. Do we have preferred high quality spark plugs for our 3.6's. I'll do some of my own research now and report back- but if anyone has experience and quality recommendations I'd love to have them, Thanks!

Note: My JT fits squarely in the date outlined in note 2 (September 2 through November 12, 2020).

 

[ShadowsPapa]

Really appreciate this information @Hootbro. Do we have preferred high quality spark plugs for our 3.6's. I'll do some of my own research now and report back- but if anyone has experience and quality recommendations I'd love to have them, Thanks!

Note: My JT fits squarely in the date outlined in note 2 (September 2 through November 12, 2020).

The spark plug is a misfire issue - not a rattle or "ping".
You can change them but the effect on any "rattle" is unlikely.

(I use Champion plugs in everything I have - Eagle, Jeep, Javelin (both) and every car I've had. I have never had any issues ever. The plugs in my wife's WK were a rare case of defects from the factory for THAT plug)

 

[Higher_Ground]

So I finally managed to fill up with premium gas (Shell 93) and hit my normal speed bump infested route.

No noise that I could tell. I will check again with the top off/windows down but seems like the issue is indeed fuel related.

Sucks because it was nearly $1 more per gallon than regular. That being said, I am going to try midgrade (89) next time and see if it's still problem free.

 

[ShadowsPapa]

So I finally managed to fill up with premium gas (Shell 93) and hit my normal speed bump infested route.

No noise that I could tell. I will check again with the top off/windows down but seems like the issue is indeed fuel related.

Sucks because it was nearly $1 more per gallon than regular. That being said, I am going to try midgrade (89) next time and see if it's still problem free.

You have problems if higher octane fuel resolves a noise. The resolution is for them to fix it, not for you to keep buying expensive fuel that otherwise has no benefit.

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