OK, usually this happen when it's hot, the a/c is on or I am towing. Lots of misfires, every 2-3 seconds, does it with bad gas, good gas, octane boost, w/o octane boost?

I just dont know why, sometimes it's more than one cylinder that is droping off, and you can feel the HP loss.

 

I have used octane boost, however not very recently, and the plugs have about 8k on them, I drive about 100-200 miles a day, fill up with gas bout' every 2 days and it does it with all types of gas. It runs clean as a wistle out the exhaust, I dont know, Thanks JMC.

 

Oh yeah, she also has 76k on her, 99'Lariat.

 

You might want to check the plug wires. My '98 had a problem with misfires and it turned out to be the wires. Ford had trouble diagnosing the problem on their equipment but a mechanic at a private garage took off the wires and inspected them and the additional handling made the problem worse. One new set of wires later, the truck is running like new again. Good Luck, GlennMc.

 

No plug wires on a 5.4L. Individual coil packs for each plug. I am only guessing that is what engine he has because of his username.

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1997 F150 4x4 Off Road, SuperCab, Short Box, 5.4, Royal Blue/Silver, K&N, Gibson SS, LT265/75/16 Wild Country APT's

 

Good observation, I guess that rules out the wires!!

 

Is it always the same cylinders misfireing? Are the coils dirty and the damp making the spark track? ( happened on old 86 of mine, cleaned the coil and its fine.) Injector wires loose?

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97, 4.6, 3.55LS, Dk red 265/75/16, Leer cap, Rhino bed, rose wood dash kit, CD player, High performance cross drilled rotors

 

Does this happen at idle too? Mine will "miss" every now and then at idle. Not while at highway speeds. Anything changed since before "it didn't used do this" time frame..... Loaned it to a buddy..... someone else drove it before you..... Can't really come up with an answer yet...

 

Have you used Octane boost before the misfires? This ***** has been known to coat the plugs and O2 sensors. If not it could be a few things. Faulty coil, plug, crank position senser or cam position sensor to name a few.

Regards

Jean Marc Chartier

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