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scanner diagnostic figures - p0301 misfire

 
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Old 12 Jul 2013, 01:31 pm
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Default scanner diagnostic figures - p0301 misfire

2007 2.4 base - 85k mi

have a p0301 cyl 1 misfire and noticeable stumble at idle. CEL blinks if left idling too long but stops if I rev the engine @ 1500+ for about 5 secs.

started after I changed the plugs to platinums during routine maintenance. left them in about a week before switching to coppers. I think the new plugs upset parts that had worn down together but was still within specs.

have done some preliminary swapping of components to troubleshoot - swapped 1 and 4 plug wires, 1 and 3 plugs, leak checked the intake, but condition persists. broke down and bought an Actron scanner and been watching scannerdanner troubleshooting videos to understand what normal readings look like.

case 1: my upstream O2 sensor readings swing but not as rapidly as online examples of good O2 sensors. scanner is regularly showing low swings BELOW .1v ... At times I'm getting .018v - high swings are about .875 -> what's the low threshold on O2 sensors? I have not checked the voltage directly.

case 2: ST fuel trim seems normal compared to online examples BUT the difference between high vs low seems twice as much as they show it should be. say -8.0 <-> +8.0 - long term trim is 0% -> -3%

case 3: TPS is 17% at idle and 68.75% WOT -> isn't 12% -> 75% normal for Chryslers? I haven't taken a voltage reading yet.

case 4: ignition advance is 12 degrees at idle and 35 degrees under normal load.

case 5: engine load is about 30% -> 35% at idle.

I'm not interested in buying parts to hopefully find the problem -> I'd rather understand what's causing the problem (before I melt my cat!)

thanks in advance!
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Old 12 Jul 2013, 06:27 pm
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Exclamation Re: scanner diagnostic figures - p0301 misfire

You didn't mention what the are plugs gapped at?....(0.040)
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Last edited by randyincctx; 12 Jul 2013 at 06:30 pm.
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Old 12 Jul 2013, 07:04 pm
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Exclamation Re: scanner diagnostic figures - p0301 misfire

between the A and the T

Quote:
Originally Posted by randyincctx View Post
You didn't mention what the are plugs gapped at?....(0.040)
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Old 13 Jul 2013, 11:04 am
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Default Re: scanner diagnostic figures - p0301 misfire

.040 - specifically used a gap tool on the coppers after such bad luck with the platinums.
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Old 13 Jul 2013, 02:57 pm
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Lightbulb Re: scanner diagnostic figures - p0301 misfire

Probably need to do some more 'process of elimination'....Start simple and go from there:P0301 help
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Old 13 Jul 2013, 05:34 pm
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Default Re: scanner diagnostic figures - p0301 misfire

went out and scanned it under a variety of conditions. this time I actually watched the live feed instead of the recordings which is a huge dif on this scanner.

my upstream o2 worked as expected, my ST trim looked funky at idle but normalized negative while holding the throttle at 2k. the tps now goes from 17% -> 75% .. would only do 69% because the floor mat was preventing the pedal from WOT. Cat does not get to 1200 degrees at idle, even with the engine warmed up. (rich misfire?)

thought about it after checking the TPS and decided to check the engine cranking at WOT -> this shuts off the injectors to clear flooding while cranking and doubles as an easy way to listen to how evenly the turns over - lazy man's compression check.

noticeable, car shaking unevenness from def one cylinder (ba ba ba boo ba ba ba boo) :/ - am leaning towards a fouled or burnt valve now ... gonna double check with the coil disconnected later tonight to verify I'm not getting partial combustion from a leaky injector which can also cause a misfire.

<sighs> we started calling dealerships to see new cars on Mon - the new Darts look pretty cool! lol
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Old 13 Jul 2013, 07:19 pm
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Exclamation Re: scanner diagnostic figures - p0301 misfire

A fellow member had a similar problem with a P0303(Misfire on Cyl#3)....He went round & round doing alot of the same things and then some to fix it to no avail.....Finally found it was a burnt exhaust valve on #3 cylinder.(Yours would be Cyl#1=P0301)...He bought a swap-out head and had a shop install it (after he got in WAY over his head trying to replace it himself,because of damn motor mounts);The valve was visibly out of round and burnished.......One of the real pros on those kinds of things is Busted_PT,he's built several PT's from the ground up!
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Old 13 Jul 2013, 08:37 pm
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Default Re: scanner diagnostic figures - p0301 misfire

yeah, I just tested with the coil disconnected and still the same shaky cranking. Also did the handkerchief over the tailpipe at idle and it sucked it in.

Am gonna call it as a burnt valve and not waste anymore time or money. I have no interest in dumping money into a car that's coming to the (obvious) end of it's natural life cycle.

Thanks for the help ppls!
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