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Discussion Starter #1
So, I've been trying to hunt down the source of my P0301 issues.
Dealership found a burnt valve - replaced the head.
Cleared codes, came back.
They swapped injectors. Cleared codes, came back, problem did not move.
I changed the coil, plugs, wires, and EGR. O2 sensors and CAT at 160K miles
Problem still exists.
Car idles rough below 850 RPM, but otherwise is fine. Has a growly rattling noise at idle.
So, I put a timing light on it, and get weird results. When the flash is consistent, it runs rough. Periodically it flashes very fast - and runs smooth.
Harness appears to be perfectly fine.

2006 Grand Caravan, 3.8' SXT, side airbags, DVD, etc, owned since new. Trying not to replace, but it also has a transmission clunk.
Of course, this all happens after I go through the entire suspension...
Synthetic oil every 5K miles, tranny service every 30K miles. Axles replaced ones, A/C compressor replaced once, P/S pump and rack replaced once (Factory warranty issue)

Timing light results really threw me.
Ideas?

TankII

Other rides:
'91+ SHO 256K miles, '01 Stratus ES 249K miles (all new suspension and now THAT's throwing codes!), '15 C-Max Energi 36K miles.
Daughter's rides '13 Avenger SXT Rallye appearance 50K miles, '09 Focus 123K miles
 

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First, is the computer turning off the cylinder, or is it just throwing a code? Of note, the cylinder can be reset by turning the car off, and then back on.

Second, if you don't have to go thru emissions inspection, you can just ignore it.
 

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How do the plugs look?
What brand of coil pack did you use? What brand of spark plugs did you use. The coil will fire two plugs at one time per https://en.wikipedia.org/wiki/Wasted_spark. You may be seeing the double spark.
 

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So, I've been trying to hunt down the source of my P0301 issues.
Dealership found a burnt valve - replaced the head.
Which valve? intake or exhaust?
Did they or you verify valve timing is not off for that cyl?

There have been several reports of cam lobe wear on these motors, not a common issue but does happen.

Was it just a burnt valve or was the spark plug also showing symptoms of improper combustion?
What's the current compression numbers? (at least on 1-3-5 bank)
 

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Discussion Starter #5
update

Cyl 1 plug is less tan than the rest.
BTW, I switched to 10W30 and STP Oil Treatment thinking the pressure was low at idle.
Exhaust valve was burnt, it would not stop pining from day one without 89 octane.
Cyl 1 compression 152
Cyl 2 compression 151
Cyl 3 compression 151
I'm putting dielectric grease on the main harness connector too.
Swapped plugs 1 and 3.

As long as the idle is above 850, it is fine, and runs strong.
Idle at start just now was 1100. Dropped to 850, and is steady.

Running rough in gear, 725 RPM. Not quite as bad as it was.
Will reset the computer and see if the code returns.

TankII
 

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Discussion Starter #6
Sorry, compression numbers were for the same bank. Swapped plugs 5 and 1.
Oh, I always use engine oil on the sparkplug threads. Have since my first Plymouth (a '71 Cricket)

It's been 15 minutes, started it up all accessories on.
Still running rough at idle, no codes yet.
I'll let you know if any show up.

Might try moving the throttle-body stop out slightly to increase the idle RPM.

TankII
 

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Cyl 1 plug is less tan than the rest.
Does it look like cyl1 is running leaner than the rest?
It could have a higher resistance in the harness for #1 injector or a connector (like the one between main engine comp. harness and injector branch) could be bad on that wire...
 

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Discussion Starter #8
The plugs have less than 10K miles on them, so to say some have a darker tan is saying they are slightly less white.
I don't see signs of preignition on these plugs, and the pinging with 87 octane is gone with the new head.
I just used dielectric grease on the main-to-injector harness connector tonight.

I have not pulled each injector and tested for resistance on the harness. Maybe another weekend, when I have help to check timing chain slack.

It runs fine above 850 RPM, no hesitation, stumble, etc.
 

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Basics:
You have verified compression.
So that narrows it to spark or fuel.

Try to swap ignition wires with another cylinder.
Then try a spark plug swap with another cylinder (not same as wire swap) Keep a record of where everything goes when swapped.
We are trying to get the misfire to move to another cylinder, and when it does, you will know your fault.

If that does not work, then I would remove the plenum and swap injectors with another odd cylinder position. Methodical deduction dear Watson...
Then perhaps a noid light to ensure the injector is getting the signal to fire.


As long as you have compression, this is going to be easy.

I recently wrote here about a Champion factory spark plug lecture I attended years ago. The representative said if you ever drop a spark plug, and really, it happens all the time, some folks more common than others.... That if you drop a spark plug on the shop floor, that you should drop it a second time.... right into the trash. The reasoning was that the shock of being dropped could cause a micro fracture in the porcelain insulator, and although it might not happen right away, that over time and heat cycles, it could cause the plug to fail prematurely. Then you or some other schmuck is chasing their tail trying to find an elusive intermittent misfire. The spark plugs may even test fire and check out in the bench tester, but under the pressure and heat insitu, they may fail in actual installed use. Drop it once, drop it twice....

Now, that being said, I would really encourage you to make positive determination of the cause of your misfire before just going out and changing all the spark plugs and hoping it goes away.
 

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Discussion Starter #11
latest testing

Recap, new plugs, wires, coil, same problem. Spark plugs were swapped yesterday (1 and 5)
So, taking FabricGATOR's suggestion, I swapped 1 and 3 at the coil.
To my dismay, I do not get any codes after 10 minutes of running and smelling lots of unburned fuel.
Ran way rougher, of course!
I put the wires back, and at 900 RPM it is surging at idle.
Waiting for it to settle to 750 is taking forever. Listening to the engine, you hear it misfiring in waves.
Does anyone think it might be a timing chain? I haven't checked the slack yet. I need to buy a new ohmmeter - mine is 30+ years and shorted out for resistance (volts and amperes are fine). When I get or borrow one, I will pull the intake and see if any of the original injectors are green.

The roughness is in waves. You can feel it doing two second smooth, two seconds rough at idle. It's not like just one cylinder is having problems at idle.
 

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What happens if you disconnect evap purge solenoid? (other than it throwing a code at you, does the idle change?)

You'd have hard time explaining how timing chain causes 2 second bursts of misfire...

The other thing that might cycle is A/C clutch, though 2 sec interval is not normal operation.
 

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Discussion Starter #13
Evap Purge Slenoid test results

So, that was an interesting test, atoman. I disconnected the evap purge solenoid, fired it up and:
Initially, the RPMs were higher than normal when 'cold' - 1200 RPM.
Eventually, it dropped to 750, but instead of 'surging' every two seconds, it just ran consistently bad. Rattling/growl of the engine was really bad in gear, almost as bad as in gear with A/C on normally - but, much more consistent. It felt like one cylinder was misfiring for sure, at least at low RPM - the thump was pretty obvious.

Note, It's not backfiring in the intake, and it smells bad at startup cold - not raw fuel, just not fully combusted.

Next up:
Need to check timing chain slack and then fuel harness.

Also:
Has anyone experienced lifters not pumping up at idle? That's why I tried the heavier oil with more STP oil treatment. I ran the last oil fill with Marvel Mystery Oil, hoping to clear up things. Assuming it's a roller-cam engine, a full set of rollers shouldn't be bad to put in if I'm running out of other inconsistencies during testing.

If I put an oscilloscope on the coil pack input wires, what should I expect? Trying to rule out false signals in the harness...

TankII
 

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Did you disconnect the vacuum line from the purge solenoid? I meant pull the electrical connector on it :) should've said unplug
The disconnected vacuum line just causes a vacuum leak..(which you can stop by plugging the end of the line)

With oscilloscope, you should compare the amplitude and 'width' of the pulse on all 3 coils (waste spark) and compare at least #1&#3 injector pulses...
 

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:Wow1:Sorry, I did not intend for you to cross wire the ignition circuitry, my thoughts were to remove the ignition wires from say [coil 1 spark 1] and swap it with [coil 2 spark 2] position and vice versa. Observing how those two ignition wires, of about the same length, ran in another physical position.
Then a spark plug.
Then try a fuel injector.
Looking for anything that makes the slightest observable change.

But just doing one thing at a time so as to be methodical. If I were to change four things at once, and I observed a change in operation, how would I know which of the four actually made the change occur?

High voltage ignition wires have a great silicon based insulation, but even new, they have a tendency to leak. Observed as corona discharge. (that is how induction sensors, such as the trigger for a timing light work) High voltage looks for the shortest path to ground. The path of least resistance. With all the silicone insulation, the plastic insulator at the wire loom, even ignition wires touching other ignition wires, or slack draped wire touching the cylinder head or valve cover can drain some of the high voltage out of the wire. Older ignition wire, the insulation qualities are broken down more. Over time, the corona can even wear a path through the insulation and across the wire loom plastic insulator to ground. I believe in isolation as much as insulation. I try to position wires so as to not touch anything if that is at all possible. Under severe conditions, touching ignition wires can even cross talk and cause pre-ignition of a cylinder that is not at the right position BTDC...

So, by swapping two ignition wires, they would likely be positioned differently, clamped into the wire loom at a different spot along the wire, touching different things at different spots. Unlikely that IF there were an HV leak path, that it would align at another possible ground opportunity. And if it did by happenstance, find a path to ground, it would move your fault to another cylinder, P0302?
Even if you had brand new ignition wires, while mostly unlikely, there could still be the possibility of a defect.

Please understand that I (we) are not standing there looking at the condition of your vehicle, nor do we know your knowledge base, skill set, experience level or even chosen career. Don't mistake my simplistic approach to removing these unknown factors from the equation. These are steps that I might take to discover why this machine is not performing as designed.

Now, anyone who inquires about the wave pattern on an oscilloscope know a tad more than say a short order cook at Denny's. That being said, I know of at least one excellent fry cook who is an amateur HAM and can repair an oscilloscope...
 

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In the old days, we would look at the engine running in the dark. If we saw ghost flashes, we knew it needed new spark plug wires. Should apply even more with today's higher voltage ignitions. If you still suspect spark, get an in-line spark flasher from Harbor Freight (~$6) and put on each plug, looking for steady flashing at idle. Of course if rpm is also varying, the sparking will also, so hard to tell cause and effect. For fuel, you can try running on starter fluid. Pull out the fuel pump relay so the injectors don't spray. If still noisy, that might be in the belt drive (esp. if yours has an AOD pulley on alternator). Idle speed is caused mainly by air flow, which the IAC controls at idle. Insure the throttle plate is fully closing at idle (no carbon, good spring) so the IAC can do its job. But IAC reacts slowly, so if a vacuum leak is changing erratically, it can't compensate. Try plugging off all vacuum ports, esp the giant hose to the power brake booster, which is the #1 suspect, #2 PCV, #3 charcoal canisters. Toughest would be a failed gasket on the intake manifold, which happened in our 1996 2.4L Voyager. Good luck.
 

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So, that was an interesting test, atoman. I disconnected the evap purge solenoid, fired it up and:

Has anyone experienced lifters not pumping up at idle? That's why I tried the heavier oil with more STP oil treatment. I ran the last oil fill with Marvel Mystery Oil, hoping to clear up things.

TankII
If you've got a lot of upper engine valve chatter/noise and you've not recently replaced the oil pickup tube o-ring then that might be the cause. This o-ring seals between the pickup tube and the block where it attaches; however, it hardens over time and begins to allow air to be pulled in since this connection point is above the oil level in the pan. Don't know if it would potentially cause missing, but maybe if it got bad enough?
 

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Here's a part number for the OEM kit with both the oil pan gasket and the pickup tube o-ring:

05241062AB

Would recommend anyone doing an oil pan gasket to go ahead and do the pickup o-ring while you are in there. If your oil pan gasket has dried-out/hardened then the o-ring likely has as well. My oil pan gasket was leaking and my pickup tube o-ring was allowing air to be pulled into the oil pump by somewhere around 145,000 miles. Drove myself nuts trying to resolve the upper engine valve-train chatter until I found out about this o-ring and replaced it. This definitely quieted down my upper engine valve noise. Your story does make me wonder if improper lash adjustment due to air pulled in around this o-ring might potentially result in damage to a valve or valve seat that could ultimately end in a burned valve?

Anyway, if needed, I believe the separate part numbers are:

04448896AB - Engine Oil Pan Gasket
06032920 - Engine Oil Pickup tube O-ring
 

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Fwiw

I just solved my P0305, and rough running issues with a new DURALAST coil pack. I got it from autozone, where I don't usually shop. First time in the life of the van I think I've fixed a misfire with a coil pack, but I'm beginning to wonder what brand pack it was I took off...
 
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