Misfiring, can't solve this. HELP!
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New User
Joined: Sep 2007
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I just did all of that for the second time 
**Update:
Now that I have checked the coils and replaced the plugs once more, it is still misfiring but UNDER DIFFERENT CONDITIONS!
Now, it can/will misfire constantly once I reach a certain engine load, i.e. in any gear at any speed if I press the accelerator past far enough it starts missing constantly.
What the heck could cause this??
**Update:
Now that I have checked the coils and replaced the plugs once more, it is still misfiring but UNDER DIFFERENT CONDITIONS!
Now, it can/will misfire constantly once I reach a certain engine load, i.e. in any gear at any speed if I press the accelerator past far enough it starts missing constantly.
What the heck could cause this??
Elder User
Joined: Jan 2009
Posts: 576
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From: Oneida, NY
my 00 5.4 did the same thing. i just got up in there and kept unplugging the coils one at a time and i got to one where when i unplugged it nothing changed so i replaced that coil and it worked. i carry new coils in the tool box. they go often unless u replace all of them. hope this helps
Junior User
Joined: Feb 2009
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Here is something else to think about. you said that it has been happening for about a year. Did it do it after you did an oil change as well? If not, how soon after an oil change did it start? Do you think that it could be a sticky valve or lifter? Had that on my '89 that caused a effect like it and wouldnt do it after oil added or changed for about a week then would come back again. chugged and spat everywhere under load but fine at idle. also maybe check your oil pump to make sure it is not going bad. No oil up top=fun ride. I know from experience and it is just like what your describing. Does it make a funny noise to go along with it? I know it is far fetched but it could be something like that. Good luck to you!!!
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From: Long Island USA
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Thread Starter
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New User
Joined: Sep 2007
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Here is something else to think about. you said that it has been happening for about a year. Did it do it after you did an oil change as well? If not, how soon after an oil change did it start? Do you think that it could be a sticky valve or lifter? Had that on my '89 that caused a effect like it and wouldnt do it after oil added or changed for about a week then would come back again. chugged and spat everywhere under load but fine at idle. also maybe check your oil pump to make sure it is not going bad. No oil up top=fun ride. I know from experience and it is just like what your describing. Does it make a funny noise to go along with it? I know it is far fetched but it could be something like that. Good luck to you!!!
I have cleaned the MAF and all connections between COPs with electrical contact cleaner, and that also did nothing.
Is it possible, just maybe, that a bad fuel injector could be doing this? I've never had one go bad on any of my vehicles, so I don't know what it would be like. Also, if I were to take them (by themselves) to a shop, how much do you think it should cost to have them bench tested?
New User
Joined: Mar 2009
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Same problem here
i've had my 99 F350 V10 crew for approx. 2 mos now and have the same random misfire. p0300 was the code but it doesn't happen all the time, only when hot and at mid 2k rpms. i'll try the suggestions, did they work? also a few questions, 1)How do you test the resistance on the coil on plugs? 2)how can i determine whether i am obd I or II?
New User
Joined: Mar 2009
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scan tool
i do not have a an o2 sensor posterior the catalytic conv. i assume you have obd 1 or do you have the post catalytic converter o2 sensor. i'm looking for a scan tool and am undecided because no co. will say it works for my 99 f350 v10 crew. still happy with yours though? this is in reference to the scan guage II post.
Last edited by rwchugger; Mar 26, 2009 at 02:11 PM. Reason: didn't go to desired user
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No, they are not.
They have an OBD-II interface. But not all are "OBD-II compliant". See the following link:
https://www.ford-trucks.com/forums/5...t-come-on.html
Up until I think 2005 or 2007, anything above 8500lbs GVWR was not required to be OBD-II compliant. The Superduty is such a vehicle.
2005, the Superduty went fully OBD-II compliant.
They have an OBD-II interface. But not all are "OBD-II compliant". See the following link:
https://www.ford-trucks.com/forums/5...t-come-on.html
Up until I think 2005 or 2007, anything above 8500lbs GVWR was not required to be OBD-II compliant. The Superduty is such a vehicle.
2005, the Superduty went fully OBD-II compliant.