I have a missfire

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Mar 7, 2006 | 08:17 PM

#16

ronbf150

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i have a f150 with a 4.2 that is miss fireing on #5 cyclinder at 45 mph and is setting a code for #5 cyclinder changed plugs and swaped wiresso those are eliminated problems help please

Mar 7, 2006 | 09:34 PM

#17

Racerguy

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From: BC, Canada

Hi Ron and welcome to the forum

How many miles on your truck? Does it use any oil or coolant?
Ever flush the injectors?

Mar 8, 2006 | 04:02 AM

#18

slc10844

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From: Baltimore

Quote:

Originally Posted by ronbf150

i have a f150 with a 4.2 that is miss fireing on #5 cyclinder at 45 mph and is setting a code for #5 cyclinder changed plugs and swaped wiresso those are eliminated problems help please

You might want to post on the 3.8/4.2 engine forum. The 4.2 has intake gasket problems, mostly associated with coolant loss. I'm not sure, but it may also affect performance.

Mar 8, 2006 | 08:36 PM

#19

ronbf150

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no coolant or oil loss the truck has 150k miles i checked for external intake gasket leaks and there is none.

Mar 9, 2006 | 04:28 AM

#20

slc10844

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From: Baltimore

If the cause of the misfire is the intake you won't see anything. The intake seals with o-rings and will suck air causing a lean misfire. Coolant loss won't necessarily be external. Vacuum can cause coolant to be drawn into the intake port of an adjacent cylinder.

Mar 21, 2006 | 10:38 PM

#21

solomon

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Joined: Mar 2005

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From: Mississippi

My truck does this too. 97 F150 4.6L with 192,000 miles. About 2 weeks ago it started. The check engine light stays on all the time because of EGR sensor or valve needing replacement. Then the truck started running rough when I'd get into the gas at higher speeds. A couple of times it's started shaking and missing bad and the check engine light has started flashing. After a couple of miles the light stops flashing, and the truck goes back to normal, but still shakes and sputters a little bit when I give it gas. I bought fuel filter, plugs and wires, but haven't put them on yet.

Mar 21, 2006 | 10:54 PM

#22

ronbf150

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i have done that I am going to swap injectors next probly this weekend. my truck is missing on # 5 cyclinder only. i will let you know what i find

Mar 22, 2006 | 04:15 AM

#23

slc10844

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From: Baltimore

Quote:

Originally Posted by ronbf150

i have done that I am going to swap injectors next probly this weekend. my truck is missing on # 5 cyclinder only. i will let you know what i find

Check for any coolant leaks around the intake manifold at the thermostat housing. Any leaks in that area will find it's way into #5 spark plug hole and cause a misfire. Do a compression check and also keep in the back of your mind Ford had a TSB on lash followers coming off on some 4.6, 5.4 and 6.8. Apparently it was a big enough problem to warrant a TSB.

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Mar 24, 2006 | 01:23 AM

#24

ronbf150

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the tsb said it would show up when it was cold but this does it all temps should i check the followers still?

Mar 24, 2006 | 04:20 AM

#25

slc10844

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From: Baltimore

Yes, I would pull the cover and check for the follower being out of place. Also check for a weak or broken valve spring. I'm not sure if the TSB refers to the follower coming out of place during cold temps or is only noticable during cold temps?