Truck started missing
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Postmaster
Joined: Dec 2007
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From: Jacksonville FL
Truck started missing
One day my truck just starting missing. It seems to only do it when cruising at 45 and when around 4600+ rpms. Any other time it doesn't do it.
Had Motorcraft platinum plugs in it. They only had 900 miles on them. I replaced them anyway and put some NGK V powers in and its still missing. Swapped my Ford racing plug wires with some backups I had and its still doing it. Dist cap and rotor are 8 months old (MSD)
CEL is not on. Fuel pressure is good.
Could the coil be going bad? If so is the MSD street fire coils any good?
Had Motorcraft platinum plugs in it. They only had 900 miles on them. I replaced them anyway and put some NGK V powers in and its still missing. Swapped my Ford racing plug wires with some backups I had and its still doing it. Dist cap and rotor are 8 months old (MSD)
CEL is not on. Fuel pressure is good.
Could the coil be going bad? If so is the MSD street fire coils any good?
Senior User
Joined: Dec 2007
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From: Noblesville,IN
Yes. I've never had a CEL but I've always checked my codes. You might wanna run a compression check too.
What compression ratio do you have and what octane # gas are you putting in it?
Any bubbles or oil in the radiator coolant while the truck is running?
What compression ratio do you have and what octane # gas are you putting in it?
Any bubbles or oil in the radiator coolant while the truck is running?
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Postmaster
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From: Jacksonville FL
Ill try and check codes when I can.
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you didnt mention if the missing at 4600 was in park and pedal to the medal or when you were driving. Dont know if its that way on a truck but on some vehicles ive been told there is a cut out at about 4000 rpm if not in gear. or at least a ford dealer mechanic informed me of this on my 97 sable. i had changed my plugs due to a slight miss and was reving the engine with gear in park to check it out and it was missing and bucking like crazy and the engine wouldnt go above about 4000 rpm.
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Postmaster
Joined: Dec 2007
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From: Jacksonville FL
It misses at about 4600 when driving. I think the limiter on the Lightnings is around 5200 rpms. Its not hitting the limiter. I have taken it to 5000 rpms alot and it never did it before.
Still need to check codes though. Haven't gotten around to it.
Still need to check codes though. Haven't gotten around to it.
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the 45 mph might be a clue, im no mechanic but I have heard people say a car is missing when the tires are out of ballance. Out of balance stuff is worse at its resonant frequency as a tire. If it vibrates bad at 45 mph it will also at twice that or 90 mph. is 4600 rpm about 90 mph? maybe you slung a balance weight and you normally drive 45. I might vibrate a little at 30 to 40 but shake like the dickens at 45. Have you changed shocks or springs or done something that would make the spring response different? just a shot in the dark. Unless you have a higher voltage more power ignition, i saw some recent posts that recommended plain old copper plugs instead of platinum as the center electrode was too small diameter for standard ignition.
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86, I forgot to ask at 45 mph what is your rpm and does it miss at the same rpm in park or neutral with the engine hot? your limiter might be less than 5200 in park or neutral. the 2 speed deal makes me think it is vibration or resonance related. this could mean air flow or mechanical weight or spring. most stuff is designed to not have resonance i its operating range. but its nice in knock sensors and the fat lady breaking the glass.
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