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  #1  
Old 02-10-2012, 01:28 PM
04mudslinger 04mudslinger is offline
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P0300

My truck has threw this code a couple of times the last couple of weeks. 210,000 miles 5.4 4x4. Cleaned throttle body, changed egr, iac as maintenance. Code came up after this. Should I look into swapping coil packs as maintenance? $320 for 8 motorcraft at dieselfiltersonline. Fuel pressure seems good. Plugs were changed 40,000 ago. It does idle a little rough, but runs strong and smooth on road.
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Old 02-10-2012, 02:07 PM
Bluegrass 7 Bluegrass 7 is offline
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Have you looked up what the code is telling you?
It will tell you 'random' missifire.
Do not begin changing coils for a 'random' missfire or look at fuel hardware. To that extent, it could be water in the gas that would be random in nature through the injectors.
First place to check is the plug seating on the crank sensor.
Use the code to tell you where to begin instead of guessing.
Random means the PCM cannot tell any 'specific' cylinder is the cause or it would tell you which one it is by a code 301 through 308.
A random indication suggest a fault common to the whole system operation.
The crank sensor, plug or harness is first in line to check out.
.
If the missfire comes under a specific set of driving conditions such as in OD under light throttle, then it could well be one coil but you have not indicated that was the case.
Sorry to get on your back but you need to think about this a bit more so you can trust useing codes and their discriptions to start troubleshooting with.
The system is smarter than your guessing would be and a lot less expensive.
One of my reasons for my being here is to get owners and readers to understand what they own and how much more they have to understand about it for self help.
Good luck.
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Old 02-10-2012, 02:23 PM
04mudslinger 04mudslinger is offline
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What I've seen on that code is since it's random, it could mean a lot of things and not pinpoint any one of them since a random is hard to trace.
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Old 02-10-2012, 03:10 PM
04mudslinger 04mudslinger is offline
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I believe both times the codes came up during idle.
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Old 02-11-2012, 12:18 PM
04mudslinger 04mudslinger is offline
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Quote:
Originally Posted by Bluegrass 7 View Post
Have you looked up what the code is telling you?
It will tell you 'random' missifire.
Do not begin changing coils for a 'random' missfire or look at fuel hardware. To that extent, it could be water in the gas that would be random in nature through the injectors.
First place to check is the plug seating on the crank sensor.
Use the code to tell you where to begin instead of guessing.
Random means the PCM cannot tell any 'specific' cylinder is the cause or it would tell you which one it is by a code 301 through 308.
A random indication suggest a fault common to the whole system operation.
The crank sensor, plug or harness is first in line to check out.
.
If the missfire comes under a specific set of driving conditions such as in OD under light throttle, then it could well be one coil but you have not indicated that was the case.
Sorry to get on your back but you need to think about this a bit more so you can trust useing codes and their discriptions to start troubleshooting with.
The system is smarter than your guessing would be and a lot less expensive.
One of my reasons for my being here is to get owners and readers to understand what they own and how much more they have to understand about it for self help.
Good luck.
This thread (https://www.ford-trucks.com/forums/6...visited-2.html) is what led me to the wanting to know about the coil pack replacement and boots. My symptoms though are that the truck is fine while driving, with engine running smooth through all the gears and in overdrive, but has slight hesitation at idle. I cleared the code Thursday, and it came back this morning. It doesn't always illuminate the SES light immediately, so I don't know when exactly it happens. Occasionally I check my Edge programmer, and the code will be there with no SES light.
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Old 02-11-2012, 04:53 PM
Bluegrass 7 Bluegrass 7 is offline
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The code by it's nature and discription is not a 'hard' fault so may not cause the CEL to light.
Some logic on why the code sets.
With the rough idle tendency you see, the crank sensor measures the crank rotation time for every cylinder everytime cylinder ignition occurrs.
So the rough idle is being detected as a random missfires due to the cause of the roughness affecting 'all' cylinders in a random fashion.
To check if the EGR may be being held open a small amount due to a faulty EVR, remove the EGR hose. If the idle settles you have an issue with the EVR sticking partly open.
Otherwise water in the fuel could be a cause of random missfire, intermittant harness plugs etc. Anything that would upset continued operation on either a momentary mechanical or temperature sensitive nature.
Fuel system issues usually do not cause a random missfire and still allow the motor to run up to road speeds without an issue.
Just takes looking from these points of view until you get it.
It may be of help to look a the live data with a scanner, beyond just the codes.
Goord luck.
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Old 02-11-2012, 06:02 PM
04mudslinger 04mudslinger is offline
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Quote:
Originally Posted by Bluegrass 7 View Post
The code by it's nature and discription is not a 'hard' fault so may not cause the CEL to light.
Some logic on why the code sets.
With the rough idle tendency you see, the crank sensor measures the crank rotation time for every cylinder everytime cylinder ignition occurrs.
So the rough idle is being detected as a random missfires due to the cause of the roughness affecting 'all' cylinders in a random fashion.
To check if the EGR may be being held open a small amount due to a faulty EVR, remove the EGR hose. If the idle settles you have an issue with the EVR sticking partly open.
Otherwise water in the fuel could be a cause of random missfire, intermittant harness plugs etc. Anything that would upset continued operation on either a momentary mechanical or temperature sensitive nature.
Fuel system issues usually do not cause a random missfire and still allow the motor to run up to road speeds without an issue.
Just takes looking from these points of view until you get it.
It may be of help to look a the live data with a scanner, beyond just the codes.
Goord luck.
Makes sense. After your describing that, I'm trying to correlate this code to the routine work (every 200,000 ) I just did with cleaning the throttle body and manifold spacer (elbow), cleaning MAF sensor, replacing iac valve, replacing EGR valve, replacing cracked hose from evap to throttle body, new CAI, new air filter, and new pcv valve and elbow. I've pretty much ruled out vacuum leaks as I've checked all my connections. I checked the coil plugs to make sure none were loose from my work. Since the code just now appeared, could it possibly be because before the cleaning the idle speed was lower, therefore making the crank position sensor not have to read as many revolutions at idle?
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Old 02-12-2012, 10:35 AM
04mudslinger 04mudslinger is offline
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Now that I think about it, my truck occasionally has a "hard" start where it takes the about the right amount of time to fire when cranking, but the fire may not be absolutely smooth every time. Is this a symptom of a crank position sensor problem?
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Old 02-12-2012, 01:00 PM
Bluegrass 7 Bluegrass 7 is offline
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Could be.
Check the sensor plug seating first.
Up front near to the A/C compressor behind the crank pulley..
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Old 02-12-2012, 07:29 PM
04mudslinger 04mudslinger is offline
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Quote:
Originally Posted by Bluegrass 7 View Post
Could be.
Check the sensor plug seating first.
Up front near to the A/C compressor behind the crank pulley..
Connection is tight. I pulled it to inspect, and I noticed the interior of the plug and the prongs on the sensor are slightly oily with motor oil. Is this normal?
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Old 02-12-2012, 09:07 PM
Bluegrass 7 Bluegrass 7 is offline
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Well not desireable but not uncommon with front crank oil seal leaks and anything coming down from the top of the motor over time.
Spray it out with throttle body cleaner and pack with a little of the special factory type connector grease to seal out the outside.
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Old 02-12-2012, 09:40 PM
04mudslinger 04mudslinger is offline
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Quote:
Originally Posted by Bluegrass 7 View Post
Well not desireable but not uncommon with front crank oil seal leaks and anything coming down from the top of the motor over time.
Spray it out with throttle body cleaner and pack with a little of the special factory type connector grease to seal out the outside.
A couple more questions, would the coating of motor oil on the prongs cause a bad connection? And is the grease you're referring to the same thing as dielectric grease?
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Old 02-12-2012, 10:58 PM
Bluegrass 7 Bluegrass 7 is offline
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Motor oil combined with dirt etc may cause poor contact.
I'm not sure what difference there is between dielectric grease and the grease used for connectors.
The connector grease is usually pure white as opposed to semi clear dielectric grease.
There is a type called NO-OXIDE-A but don't think you could ever locate any on the consumer market.
It's used in industry for battery buss bar connections in high current power systems and sticks like permant and totally water resistant and very sticky.
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Old 02-14-2012, 09:31 PM
04mudslinger 04mudslinger is offline
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Quote:
Originally Posted by Bluegrass 7 View Post
Motor oil combined with dirt etc may cause poor contact.
I'm not sure what difference there is between dielectric grease and the grease used for connectors.
The connector grease is usually pure white as opposed to semi clear dielectric grease.
There is a type called NO-OXIDE-A but don't think you could ever locate any on the consumer market.
It's used in industry for battery buss bar connections in high current power systems and sticks like permant and totally water resistant and very sticky.
I cleaned it with electronics cleaner and added dielectric grease to the contacts. So far, so good. I've also added seafoam to my gas tank, and it seems to have smoothed out.

Also, my tranny seems to be downshifting more normally since I've put more miles on the reset computer. After I got the p1740 code and I reset it, it seemed to have corrected itself.
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Old 02-15-2012, 12:14 AM
Bluegrass 7 Bluegrass 7 is offline
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It's been quite a learning curve for you.
Hope the TCC code does not come back to haunt.
Once there is a detected issue it usually does not fix it's self permantly.
The PCM constantly monitors for shorts, opens and slow or stuck operations by looking at the operating current 'signiture' during operation by comparing to an information table in software, but good luck to you..
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