Misfire on #7 AGAIN
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Elder User
Joined: Sep 2004
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From: N. Georgia
Misfire on #7 AGAIN
My son's truck. 1997 F150 XLT 5.4 Auto. This is a problem that keeps rearing it's ugly head. About a month and a half ago the truck started to run extremely rough. Pulled the codes with Auto Enginuity and it said #7 misfire. Cleared the codes and test drove it. Ran fine for about 3 miles and then it started doing it again. Pulled the codes again, same thing so we replaced the #7 COP and all 8 new plugs. The truck ran fine for a week and then it started it again. Pulled the codes, it was #5 this time. Bought another one and replaced #5. Fast forward 1 month. It started running rough again, scanned code for #7 misfire. Cleared the codes and it runs fine. Took it on a 30 minute drive and everything is fine.
The question is, what causes it to start running rough and set this code and then why does it go away when I reset it. Nothing else done to it, just reset the codes. It has to be something that is causing the cylinder to start misfiring other than the COP failing. Wiring to the COP maybe? And then how does clearing the code make it clear up and start running right?
HELP. This is his daily driver for work and he's getting fed up with it crapping out on him.
Joe
The question is, what causes it to start running rough and set this code and then why does it go away when I reset it. Nothing else done to it, just reset the codes. It has to be something that is causing the cylinder to start misfiring other than the COP failing. Wiring to the COP maybe? And then how does clearing the code make it clear up and start running right?
HELP. This is his daily driver for work and he's getting fed up with it crapping out on him.
Joe
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Elder User
Joined: Sep 2004
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From: N. Georgia
Here's an update. From a cold start today it reset the ses light within 15 minutes. If you read the codes and erase them the truck will run fine.
Anybody have any ideas on this? Joe
Anybody have any ideas on this? Joe
Hotshot
Joined: Jul 2005
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erasing the code does not make the truck run better. if you have an oops or upset, you get a code recorder that tells you what it was. it may go away on its own, it may be intermittant. the light just tells you a code has been recorded. what type plugs did you use? the 5.4 seems to like Motocraft better than others.
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Elder User
Joined: Sep 2004
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From: N. Georgia
The truck will be back at my house tonight so I'll work on it again when I get home from work. I don't remember which brand of plugs they were but I'll look tonight. They were platinum but weren't Motorcraft, that much I know. I did use dielectric grease on the boot but maybe I didn't use enough. I'll pull the COP tonight and check on the moisture.
Thanks for the help, Joe
Thanks for the help, Joe
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Elder User
Joined: Sep 2004
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From: N. Georgia
OK, here's the latest. Pulled #7 COP and the hole had water in it. I have no clue where it came from. Dried the COP off and the water out of the hole, re-greased and swapped #7 and #6 around and reinstalled them. Same thing happened again. Drove for a mile and it started again #7 misfire. Saturday we'll buy a new Motorcraft plug and replace the #7 plug (Bosch platinum in there now). Does anyone have any other suggestions on what to do or how to test this problem.
Joe
Joe
Freshman User
Joined: Jul 2006
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I had a similar problem. Is there a k&n if too much oil gets on it and in the mass air flow sensor. your computer can go haywire.
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Elder User
Joined: Sep 2004
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From: N. Georgia
No. No K&N, straight factory paper filter. Maybe it's the mass air flow anyway. Any clues how to test it?
Thanks for your help, Joe
Thanks for your help, Joe
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Elder User
Joined: Sep 2004
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From: N. Georgia
Here is the end to the story (I HOPE). Pulled#7 COP to replace the plug with a Motorcraft brand (we wound up having to go to Ford $11 for 1 plug). The hole still had a little water down in it. Blew it out and then vacuumed it out. Changed the plug and so far it's gone 15 miles without messing up. Maybe it's fixed, we'll know next time it rains. Still can't figure out where the water comes from.
Thanks so much for y'alls help, Joe
Thanks so much for y'alls help, Joe
New User
Joined: Apr 2020
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Water in plug
I had a similar problem on my 97 F150. I finally found that water was leaking in around the windshield washer nozzles that are located on the hood. I put some clear silicone around the base of the nozzles and problem solved.
Tuned
Joined: Apr 2001
Posts: 467
Likes: 25
From: Central Callifornia
Yeah, I remember the 5.4s had a problem with water leaking down into the #7 causing misfire. Can't remember a specific source.
