Missing Under Load - Bucking

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Dec 30, 2005 | 07:13 AM

50th ann

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From: Royal Palm Beach, Fl

Missing Under Load - Bucking

My 1998 4.6L F-150 with 159,000 Miles started missing under a load. While driving at a steady 45- 50 MPH on a flat road it would miss while trying to speed up. (before the downshift) The miss would cause the truck to buck untill it down shifted. Last night I changed the Spark Plugs and that seemed to fix it except while in passing gear the miss and buck are present. I bought the truck new and do all my own maintenence but I have not done anything with the fuel injectors. They must need some type of maintenence by now but I'm not sure what I should do. I add injecftor cleaner every now and then but there must be more I can do.

Any Help Would Be Appreciated

Dec 30, 2005 | 12:53 PM

LxMan1

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From: Louisville,Ky.

Have you replaced the wires yet?

Dec 30, 2005 | 07:35 PM

GreenHornet79

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I had a very similar problem with my '98 F150 that has a 5.4. My problem amounted to a coil going bad. I would suggest looking at the forum section that deals with the 1997-2003 F150. There have been quite a few posts recently about dealing with engines misses. Maybe these will give you a direction or some ideas to check out. Good luck.

Dec 31, 2005 | 05:38 AM

50th ann

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From: Royal Palm Beach, Fl

The wires are twenty five months old. (45,000 miles)

The new spark Plugs fixed most of the miss. Now it's just under high rev's that it spits and sputters a bit. It's not a steady miss it seems to move around in the firing order.

I have two coil packs. My 1998 4.6 l engine is prior to the coil on plug design.

Can coil packs do that?

Last edited by 50th ann; Dec 31, 2005 at 05:43 AM.

Jan 5, 2006 | 02:03 PM

skilife17

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From: Cottage Grove, Minnesota

50th ann

My 1997 4.6L did the same thing and at the same speeds. Even had a miss when cruising at 70 going up a slight hill on the highway. Set missfire code. I replaced both plugs and wires with motorcraft and runs great. If you changed plugs wires should have been done also.

Jan 5, 2006 | 05:44 PM

ChevmaninaFord

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From: Gray's Creek, NC

My truck used to "buck" under a load, the problem was not the ignition, it was something my mechanic called torque converter chatter, he changed the transmission fluid and put in some kind of additive and it has not ever "bucked" since. Mostly the "bucking" came as I was going up hills while the truck was in overdrive. The mechanic is a very reputable one here in Fayetteville, NC.