1998 Ford F-150 Cylinder misfire at acceleration

Tiny
JAYBEEZMAIL
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  • 1998 FORD F-150
Engine Performance problem
1998 Ford F150 V8 Two Wheel Drive Automatic

Truck seems to idle perfectly. Usually runs strong for about a mile, then it starts to vibrate at acceleration only. Then seems to cruise fine until I accelerate again. Replaced fuel filter, oil and filter, plugs, plug wires, tested the 2 coil packs, repaired (I think) leak in pcv hose - will check it again. Coded a misfire on cylinder #2. Tested resistance on fuel injector and the wiring harness is producing 12 13 volts. When I cleaned the wire harness that connects to that injector, the problem went away for about a month but now I can't seem to replicate that. Problem persists. Also checked fuel pressure. Could this be that pcv hose or might it be a problem with the cylinder itself?
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Tuesday, May 18th, 2010 AT 12:40 PM

11 Replies

Tiny
BMRFIXIT
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Check if coil firing the cylinder
check if injector pulsing
check compression
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Tuesday, May 18th, 2010 AT 8:13 PM
Tiny
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Thank You. I did pull the wire from that plug while running. It was sparking. I put a long screwdriver to the fuel injector and it was clicking like the others. I also pulled the rail up and applied 12 volts to that injector and it sprayed well. Compression - I guess I'll have to pay for that. Or is there another way to check it?
Thanks again!
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Tuesday, May 18th, 2010 AT 9:48 PM
Tiny
BMRFIXIT
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You can buy or rent one

not much money to rent or buy the gauge
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Tuesday, May 18th, 2010 AT 10:18 PM
Tiny
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Okay, I see I can get one for like $20.00. I'll do that. What keeps throwing me though is the fact that each time I removed the injector wire harness from that cylinder ( when checking plugs, replacing plugs, testing plug wires, replacing plug wires) the car ran perfect for days. When I then cleaned and scraped the injector contacts, it ran perfectly for over a month. Seems to have had an effect. Could that just be coincidence? The harness does provide 12 volts and the injector does function. Just seems odd to me. Any thoughts?
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Wednesday, May 19th, 2010 AT 12:23 PM
Tiny
BMRFIXIT
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A leaky injector may be at fault mark the injector and switch it with another good cylinder
if code move on with the injector
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Wednesday, May 19th, 2010 AT 5:09 PM
Tiny
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Excellent. I was thinking about trying that but never thought about a leaky injector. Thank You, I'll give that a shot.
Jaybee
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Thursday, May 20th, 2010 AT 10:12 AM
Tiny
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Well, I swapped fuel injectors for cylinders #1 and #2 - the original code was #2 misfire - had the code checked again, and this time I get #4 misfiring. It is on the same fuel rail, so when the engine cools down, I'll pull that rail again and see if I got gunk on that #4 injector when I lifted that rail to swap #1 and #2. Any others thoughts anyone?
Oh ya, they also told me the DPFE is definitely bad, but would not cause this problem.
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Friday, May 21st, 2010 AT 2:53 PM
Tiny
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Just checked and cleaned the injectors. I took it for a ride and it ran smooth but not quite perfect for about a mile. Then, it started shaking hard at acceleration, the CEL started flashing, then settled into a solid on. Am I looking at electronics here possibly?
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Friday, May 21st, 2010 AT 5:13 PM
Tiny
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After reading some other posts, I decided to try unplugging the egr valve and blocking both ends. (Hose and tube where it connects to egr), took it for a ride and got the same thing. Idled great and ran great for about a mile, then started missing horribly upon acceleration. At that point, it may be missing the whole time, but it runs along so smooth until you accelerate that you cannot tell. So, does that rule out any egr issue, or did I do the test wrong?
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Sunday, May 23rd, 2010 AT 11:28 AM
Tiny
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OMG, I may have just discovered my problem! We'll see. I went to pull my currently misfiring plug #4 out and discovered there was oil surrounding my plug deep down in that hole. That reminded me that one of the first things I suspected was the oil I found around my #2 cylinder. I forgot, because I steam cleaned the area and it never came back. I don't know, perhaps that small leak plugged itself and the oil forced itself out in another place - I understand old gaskets can do that. So, I cleaned it all up and added quite of bit of dielectric grease in and around the boot. I just drove a few miles and it feels like a brand new truck. When I got back and looked at #4, there was no oil around it. Maybe it's a very slow leak. So, I am assuming this would be the valve cover gasket? Your opinion would be appreciated.

Thanks for all the advice bmrfixit!
Jeff
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Sunday, May 23rd, 2010 AT 1:00 PM
Tiny
BMRFIXIT
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Good news
clean it and happy driving
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Monday, May 24th, 2010 AT 5:37 AM

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