I have a 2007 with the 4.6. It has started sounding like it is miss firing around 1000-1500 rpm. It also is doing it at idle. So far I have not found and vacuum leaks. I have replaced the mass air meter, the pcv valve and the EGR valve. Last year about this time I put new plugs and coils on it. It is not sending any error codes so I am stumped. No sign of a blown head gasket. Also under hard acceleration it is hardly noticeable or not even present. Any help would be greatly appreciated.

 

what brand/model plugs and coils?

what did you torque plugs to?

have you removed and properly cleaned TB?

 

About to do the throttle body cleaning. The plugs were Bosch OE Iridium 9606 and the coils were summit racing FOMOCO 850570-1R. I use the shop manual regularly so I would suspect I torqued them correctly but at the moment I could not tell you what it was to.

 

If cleaning TB doesn’t solve your issues, I would consider installing a new set of MC plugs and reinstalling the factory coils (with new boots/springs, or at least ones off current coils) if you kept them.

 

I think you can determine whether it's caused by a malfunctioning plug, coil or injector starting by removing each wire connector, one at a time. If any injector wire removal does not affect the idle, that's the cause. If any coil wire removal does not affect the idle, you'll then need to test futher to detect whether it's a coil or plug. I'd retest if one is bad, and inspect the connector and nearby wiring before replacing the part.

 

without any codes being thrown, I would doubt that he has a totally dead cylinders. But still nothing wrong with trying what you describe. If nothing else, it will make you test the wiring plug connections.

but if it were mine I’d want to get rid of those plugs, torque down new MC plugs, and ideally get rid of the summit coils, go back to oem coils with fresh boots/springs.

Hope he figures it out and reports back what fix is.

 

Cleaning the throttle body did not help. I eventually replaced the plugs and checked the coils. Also I went ahead and replaced the injectors. I know one went bad before I had the truck and was replaced so I figured why not do them all so they are new. I used factory oe. It seems better for now. I will give it a few days of driving before I am satisfied.

 

Problem is still there. Today I changed the crank position sensor and the fpdm. Still having issues. I guess I'm about to change the coils back to oem and maybe replace throttle body. I'm running out of ideas.

 

Firing that parts cannon.. Do what Later said, Motorcraft plugs and OEM coils, new boots and springs.

 

07 with a 46
First thing is to try to narrow the miss down to a cylinder with a code test
If code 300, then a few parts to start with
All Motorcraft ignition parts for sure
Silicone dielectric grease in the new boots
Then you swap a coil around or start shorting out / disconnecting injectors and coils
Noid lamp test
Good luck
007