2004 F-150 Shutter
 

I have a 2004 F-150 5.4 3 valve with 170K miles. I am getting a shutter at highways speed only when the truck is hot and somewhat under load . I checked the transmission fluid , it's right at the full mark and it looks clear, cherry red. I changed the plugs at 110K miles had three break off but I did not replace the coil packs. I went to both Auto Zone and Advanced Auto to have the codes read both readings did not yield any codes or issues. I do have a intermittent tick that comes and goes. What could be the possible causes? Where should I start at the transmission or another plug change along with new coil packs? I appreciate any help. Thanks Glenn

I would do plugs and replace the coil boots. Would not do coils yet if I was trying to save money. If I was trying to keep it fresh, I would go ahead and change the coils. I would also check for an injector leak.

Agree, replace the plugs with Motorcraft SP-515, and replace the coil boots and springs. These are available as a kit.

http://www.rockauto.com/en/moreinfo....422751&jsn=444

What coil packs would you recommend? Thanks Glenn

I'd recommend Motorcraft.

However, I'd replace the plugs and boots/springs first. The factory coils don't go bad very often.