I browsed around and saw many similar issues -- but, here goes anyway...

I am getting medium to major shuddering/misfiring/knocking (any difference?) when driving under light load (and now starting to see/feel it at idle) -- primarily up around 40-60 mph. It stops when I goose the gas, but comes back when the revs go down.

Had the same thing a while back and the "service engine soon" light came on. They (not a dealer) replaced a coil and things were great. Now, it's back but without the engine light coming on. I took it back in, and they told me it's probably the same identical problem, but without the engine light/error code, they wouldn't be able to know which coil to replace.

I'm not any kind of a gear-head, so forgive the rambling.

Still, this sucks and I spend most of my time at those speeds and under light load, so I'm getting the knocking/misfiring/shuddering (whatever!) all the time and hate it.

Is there anything I can do? I normally use 87 Octane and just recently put in some STP fuel injector cleaner hoping that would help.

Any advice?

 

Change your plugs and wires. It's a pretty easy job, all you need is a 3/8 drive ratchet, a 6 inch extension, and a plug socket. Swap them one at a time so you can get the wires back in the correct places. If you want to know how the PCM senses a misfire, search my posts, I have an extensive write up somewhere. Good luck.


BTW, yes there are differenced in shuddering/misfiring/knocking...

Edited to add: Just realized you have an 02, therefore no wires... Just change the plugs...

 

Before you change the plugs, pull the coils one at a time and blow out the recess around the plug to remove any water (causes the coil to short). I have an '02, and have had to do this several times, either after washing engine or after driving thru deep enough water to splash into engine compartment. If you don't have a compressor, pull the plug and turn over the engine to blow out the water. If you don't find any with water, then go ahead and change plugs.

 

I have a 2001 with the 4.6 engine and have been thru this already. At about 100,000 miles the first coil went bad. I had Ford change the plugs and one new coil. After that the coils starting going bad one at a time until I changed the last 5 all at one time.
Now with 180,000 miles it is starting again. As for changing the plugs Ford quote 3 hours labor as the last 2 plugs on both sides are under the fire wall and are extremely hard to get out.

 

Do yourself a favor - search the engines forum for "COP's Deal" (I left a link there)- That will give you the link to Global Automotive. Get yourself a set of 8 COP's for $100 and replace them all at the same time and you won't have to worry about it for a long time. Your COP's are weak - It will feel as tho you have a new motor under the hood after changing them all out.. There cheap if you know where to get them and I think I just told yuh - Good Luck....

 

Thanks, guys. This is just what I was hoping for. I'll follow your advice over the next few days and will let ya'll know how it turns out.

Cheers!