My 98 F150 (5.4L) suddenly started to miss and shudder yesterday. It has 123k miles. Feels like a plug went bad or a plug wire fell off. Poor acceleration, but no backfire.

I took it to my local Ford dealer and they said they had to replace the CPM (?) before they could diagnose the real problem. At an estimated $600, this seems extreme.

Anybody got a suggestion to get a better diagnosis?

Should I replace the spark plugs first? injectors?

I feel like I have to spend $600 just to find out it's probably a minor problem.

When did you do your last tune up? The CPM, as you probably know is the Computer Module... I would recommend taking a compression test to see if there might me a compression leak. Also check to see if you have a vacume leak. If you are not good at working on your own truck.. Check out a second opinion.. Remember, one Doctor may not know what is wrong, but with a second opionion, who knows, maybe you will find out what is really wrong. I would seek a second opinion. Just my 2cents worth. Carl