06 Missfire

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Mar 31, 2013 | 12:55 PM

jer365

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06 Missfire

I know I am in the wrong forum but have gotten no response from the correct one.
my 06 f-150 5.4 v-8 has a misfire in #4 the mechanics that I have taken it have no clue what else to change, we have done the plugs twice and 2 of the fuel Injectors, still has the missfire around 50-65 initially but then it seems to be only around 70 - 90 if I get on it. Help please.

Mar 31, 2013 | 08:26 PM

Ford_Six

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From: The Big, Oregon

How is the compression on that cylinder, and is there any valve noise?

Mar 31, 2013 | 08:32 PM

jer365

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They have not checked the compression that I know of, have replaced sp twice, and fuel injector on that one as well as number 8. What noise would the valve make?

Mar 31, 2013 | 09:23 PM

fixnair

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From: Sapulpa OK

A burned valve wouldn't make any discernible noise. An experienced auto tech could probably hear a burned exhaust valve in the exhaust pipe. I Had an '02 Lincoln Continental, 5.4 that kept throwing a cyl #6 misfire. Like you I swapped injectors, plugs and coilsW/O success. I finally gave the engine a compression test and #6 cylinder was way down to 60 psi.

Last edited by fixnair; Mar 31, 2013 at 09:25 PM. Reason: Add'l info

Mar 31, 2013 | 09:54 PM

jer365

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have not done a comp test on 4 did on 8 when it was misfiring but that was normal, thinking a valve spring is what the mech said tonight does anyone know of a way to test the spring to be sure?

Apr 1, 2013 | 01:16 AM

Ford_Six

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From: The Big, Oregon

It'll just not close the valve, so the compression will be very low. You can pull the cam covers and visually inspect everything, but that will take time.
By valve noise I mean a ticking indicating there is extra clearance somewhere.
What is the vehicle actually doing when the check engine light comes on, or when it's obviously misfiring? Rpm, throttle position, etc-

Apr 1, 2013 | 02:02 AM

paverunner

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Once the local guys give up your on your own. Think! I would go spark plug wire, distributor cap contact,fuel pressure, etc. Make friends with a real mechanic.
G