Spark knocking on acceleration grand caravan

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PCV valve stuck open leaning out intake.
Plugs too hot.
Vacuum leak.
Funky coil pack(s) or wires.
Low fuel pressure.
Clogged fuel injector(s).
Bad O2 sensor.
 
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Okay, I had a T&C with the same 3.8L many years back that had the same symptoms as your van is exhibiting. Turned out to be the CMP and CKP sensors. On your year model you need a DRBIII to check the specifics of the timing cycles, but changing the sensors is really cheap and pretty easy. Just clean the areas around the sensors BEFORE you remove them to prevent debris from getting inside. Also, the PCV valve is a good thing to change as well (easy to check too) BUT make sure you have replacement hoses and gromments for the PCV valve before you attempt to remove it (ask me how I know...).

These engines have a timing chain, so the odds of the chain jumping is pretty slim. Also, have you checked the transmission flexplate (through the trans inspection port) to see if your flywheel is cracked? Pretty common issue (it is a "flexplate") with the 4th Gens for some reason - usually noticeable by the sound it makes, but in some instances no sound will be made but will affect the timing as the CKP reads off the flexplate.

From Chiltons: "The crankshaft position sensor detects slots cut into the transmission driveplate extension. There are 3 sets of slots. Each set contains 4 slots, for a total of 12 slots. Basic timing is set by the position of the last slot in each group. Once the Powertrain Control Module (PCM) senses the last slot, it determines crankshaft position (which piston will next be at TDC) from the camshaft position sensor input. The 4 pulses generated by the crankshaft position sensor represent the 69°, 49°, 29°, and 9° BTDC marks. It may take the PCM one engine revolution to determine crankshaft position."

Here's a video of a Dodge Journey with a flexplate issue (watch at the six minute mark forward) that can cause timing issues:




Now, before anyone says "it's not knocking" that is not always a symptom of a cracked flexplate; most the time - yes, but still possible without the noise. Anyway, that's a worst case. Change out the sensors first and I suspect that will fix your issue. If not, then post back and we can try more on the repair tree.
 
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Okay, I had a T&C with the same 3.8L many years back that had the same symptoms as your van is exhibiting. Turned out to be the CMP and CKP sensors. On your year model you need a DRBIII to check the specifics of the timing cycles, but changing the sensors is really cheap and pretty easy. Just clean the areas around the sensors BEFORE you remove them to prevent debris from getting inside. Also, the PCV valve is a good thing to change as well (easy to check too) BUT make sure you have replacement hoses and gromments for the PCV valve before you attempt to remove it (ask me how I know...).

These engines have a timing chain, so the odds of the chain jumping is pretty slim. Also, have you checked the transmission flexplate (through the trans inspection port) to see if your flywheel is cracked? Pretty common issue (it is a "flexplate") with the 4th Gens for some reason - usually noticeable by the sound it makes, but in some instances no sound will be made but will affect the timing as the CKP reads off the flexplate.

From Chiltons: "The crankshaft position sensor detects slots cut into the transmission driveplate extension. There are 3 sets of slots. Each set contains 4 slots, for a total of 12 slots. Basic timing is set by the position of the last slot in each group. Once the Powertrain Control Module (PCM) senses the last slot, it determines crankshaft position (which piston will next be at TDC) from the camshaft position sensor input. The 4 pulses generated by the crankshaft position sensor represent the 69°, 49°, 29°, and 9° BTDC marks. It may take the PCM one engine revolution to determine crankshaft position."

Here's a video of a Dodge Journey with a flexplate issue (watch at the six minute mark forward) that can cause timing issues:




Now, before anyone says "it's not knocking" that is not always a symptom of a cracked flexplate; most the time - yes, but still possible without the noise. Anyway, that's a worst case. Change out the sensors first and I suspect that will fix your issue. If not, then post back and we can try more on the repair tree.
This is what happened to me on a mid 2000’s Chrysler I had. The flex plate cracked but still ran and drove decent but it threw off the timing. I was getting ckp code and replaced it but code stayed until one day the flex plate broke completely and left me on the side of the road.. I also thought the noise was spark knock or something like that and replaced a bunch of ignition components.
Edit this was years ago and I did not know at the time the flex plate was cracked (never even heard of such an issue) so I replaced everything regarding to spark and even emissions..
 
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Try running something through a vacuum line, to remove possible carbon buildup on your pistons; an Italian tune-up may also help.
 

ram_man

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So an update. I replaced the aftermarket EGR valve with a Mopar EGR valve since the quality of be aftermarket EGR valve that I had installed earlier this year had some questionable quality concerns ....no luck still spark knocks, that's what it sounds like any way. Something I did notice is that it seems to have the problem worse when the gas level is below half a tank. From fuel to 1/2 it won't do it or if it does it's very subtle and minor. Below half it starts to do it more often.
There isn't an easy way to check fuel pressure. Fuel trims look good. short term fuel trim is between +3 and 0 long term is +5 at most. When you drive it they don't go much in the negative either and are pretty stable and decent. Plugs are newer wires are new, coil seems ok, no codes, no vacuum leaks. I'm at a loss. Maybe a fuel pump getting a hair weak? I hate to replace it and not be sure though.
 
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So an update. I replaced the aftermarket EGR valve with a Mopar EGR valve since the quality of be aftermarket EGR valve that I had installed earlier this year had some questionable quality concerns ....no luck still spark knocks, that's what it sounds like any way. Something I did notice is that it seems to have the problem worse when the gas level is below half a tank. From fuel to 1/2 it won't do it or if it does it's very subtle and minor. Below half it starts to do it more often.
There isn't an easy way to check fuel pressure. Fuel trims look good. short term fuel trim is between +3 and 0 long term is +5 at most. When you drive it they don't go much in the negative either and are pretty stable and decent. Plugs are newer wires are new, coil seems ok, no codes, no vacuum leaks. I'm at a loss. Maybe a fuel pump getting a hair weak? I hate to replace it and not be sure though.
If the fuel pump were having trouble keeping up, I’d expect lean fuel mixture and cylinder misfire DTCs or something similar to get set.

If you have the ability to view PIDs other the fuel trims, log the knock sensors’ output and see if the audible noises you hear correspond to extreme spikes in those sensors’ voltage readings. If not, time to investigate broken or loose engine/suspension/exhaust parts as the source of the noise I think.
 

ram_man

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If the fuel pump were having trouble keeping up, I’d expect lean fuel mixture and cylinder misfire DTCs or something similar to get set.

If you have the ability to view PIDs other the fuel trims, log the knock sensors’ output and see if the audible noises you hear correspond to extreme spikes in those sensors’ voltage readings. If not, time to investigate broken or loose engine/suspension/exhaust parts as the source of the noise I think.
I've already checked the suspension not for this but just to be proactive. The noise is definitely an engine noise and corresponds directly to throttle input.
 

OVERKILL

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So an update. I replaced the aftermarket EGR valve with a Mopar EGR valve since the quality of be aftermarket EGR valve that I had installed earlier this year had some questionable quality concerns ....no luck still spark knocks, that's what it sounds like any way. Something I did notice is that it seems to have the problem worse when the gas level is below half a tank. From fuel to 1/2 it won't do it or if it does it's very subtle and minor. Below half it starts to do it more often.
There isn't an easy way to check fuel pressure. Fuel trims look good. short term fuel trim is between +3 and 0 long term is +5 at most. When you drive it they don't go much in the negative either and are pretty stable and decent. Plugs are newer wires are new, coil seems ok, no codes, no vacuum leaks. I'm at a loss. Maybe a fuel pump getting a hair weak? I hate to replace it and not be sure though.
Stupid question:

How easy is the fuel filter on this to replace?
 

ram_man

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Oh, that's funky! My Ford stuff has always had both, haven't owned a Mopar long enough for it to be a concern for me as of yet.
I don't think any Chrysler has had a fuel filter since the mid 90s I could be wrong but I do believe they got away from them on most if not all vehicles.
 

OVERKILL

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I don't think any Chrysler has had a fuel filter since the mid 90s I could be wrong but I do believe they got away from them on most if not all vehicles.

I just looked, looks like they integrated the filter in the regulator in the early 2000's, putting it on the top of the tank as part of the pump assembly for the Cherokee and Wrangler:
30961_jee_4.jpg


Interesting move.... lol.
 

OVERKILL

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It looks like yours MIGHT be the same way? I'm just whinging it with some pics from Rockauto here:
E7172M-1__ra_p.jpg


But going lean when fuel level is low(er) can point to a plugged fuel filter or pick-up assembly. It's too bad monitoring FP sounds like it's not viable, as that would help confirm whether that could be the culprit or not.
 

ram_man

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It looks like yours MIGHT be the same way? I'm just whinging it with some pics from Rockauto here:
E7172M-1__ra_p.jpg


But going lean when fuel level is low(er) can point to a plugged fuel filter or pick-up assembly. It's too bad monitoring FP sounds like it's not viable, as that would help confirm whether that could be the culprit or not.
Yeah they don't make it easy no test port or pid information..... Ugh
 
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