Misfire at idle and WOT...sounds fine otherwise

[98L36]

As funny as this sounds it's the best I can describe it. If you leave the car sit and idle for a few minutes the SES light will start blinking and I'll get a code for a Cyl 4 misfire. Just a few months ago it had a brand new set of wires due to a misfire on Cyl 4. The "old" misfire was way worse, you could clearly tell it wasn't firing right and the SES light would come on even under light load (i.e. 2k RPMs). Got checking things and eventually found a bad wire, that's why it got a new set.
Now it's back though, same Cyl 4 too. For the life of me I can't figure out what would cause it to only throw a blinking SES light only at idle and WOT though. It doesn't do it driving down the road, matter of fact it purrs like a kitten when you're driving....but if you let it idle or get the RPM's up high (like WOT runs) the light comes right back on. :th_nervous:

My only guess is an injector or maybe bad plug. Any other ideas?

 

[blueguy]

You changed the wires...but not the plugs?

-_-

Go get some AL606's and gap em @ .050"

Done and done.

 

[dsmuts]

Pull your plug and look at it. Run some seafoam through it while your at it.

 

[98L36]

It's had seafoam already......twice in the past 8ish months with latest treatment being maybe 2 weeks ago (I'd bought 2 bottles originally and never used the 2nd one till then).

Will have to get plugs though. I know the last time this happened they all looked fine, that's why I went wires w/o plugs. We'll have to see though.

 

[dsmuts]

plugs are cheap id replace them if i had them out

 

[98L36]

I'm going to assume that platinum (or double platinum) plugs are a waste of $$ ?

-Edit-
And just curious what difference it will make gaping them at .050" instead of the .060" that I'm seeing everywhere else?

 

[FordMan77]

These motors don't like platinum plugs, so don't waste the $$. Either copper or iridium (factory) is best. I went w/ NGK TR55 V-Power plugs in my 00 GT and it runs just fine, and gapped at .050. They just run better at .050 from what I've read/seen.

 

[98L36]

Ok, well it looks like AL 606 copper's might be in store.

Btw FordMan, congrats on 1,000th post.

 

[blueguy]

Smaller gap = less chance of a misfire.

Factory gap of .060" is fine, but .050" is lazy status.

I'd do...

AL606's gapped at .050"
New Wires, just because they are cheap...Autozone's lifetime warranty ones are great.
Sand down the coil pack terminals...wipe clean and apply a small amount of dielectric grease on them.