engine missing out at 50mph

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Mar 27, 2013 | 01:01 PM

shockr4

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Joined: Mar 2013

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From: Derby Kansas

engine missing out at 50mph

I have a Ford F150 5.4L lariat 2 wheel drive with 78,000 miles on it. I just had new platinum plugs put in and a new air filter along with the routine LOF service. I had the plugs changed because I was experiencing some missing out at 50 MPH. The check engine light was not on. The mechanic said that one plug was definitely bad.

I have had the truck back for a week now and today while driving it I had the same missing out at 50MPH. The check engine light is not on. I had the cruise control on when it happened so now I am wondering if it could be related to the cruise control?

Any ideas on what else It could be?

Mar 27, 2013 | 02:01 PM

1979 Ford

Cargo Master

Joined: Jul 2005

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From: Not as far west as I want

I coil pack might be on the way out or there is a vacuum leak. Either may or may not trip a CEL.

Mar 27, 2013 | 02:14 PM

shockr4

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Joined: Mar 2013

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From: Derby Kansas

Thanks

Thanks Snoopy! Any idea on how many miles to expect on a COP?

Mar 27, 2013 | 11:31 PM

twfish

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Joined: Jun 2011

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Coil pack is going bad. At 50 MPH the engine is still at a load from o/d wich is hard on coil packs in the first place. Best thing to do is buy 1 new coil pack and put it on number 1 cylinder (since its usually that one that goes out first) if that doesn't help it put the old number coil pack on number 2 cylinder and try that, no success continue on until all cylinders have had a different coil pack. If it doesn't work you have more than 1 coil pack bad and you will have to redo process with 2 coil packs. There easy to change, just have some silicone lube and put between the plug.