Changed plugs, now runs like crap...
 

Please help. First spark plug change-something is wrong.


1998 F150 4.2 123,000 miles.

Had recently replaced the PCV elbo that was dry rotted & had a hole sucking air.

Decided to change the plugs since it was still running a little rough at idle.

Got a set of Motorcraft SP-504 finewire platinums. Pulled the old Autolite set out one at a time & replaced them. One had a bunch of crust burnt stuff on the tip.

Now I know I did not mix up the wires since I did them one at a time. But now the truck runs like crap. A low idle shudder & muffler sounds like it's going to backfire.

Figured it must be the wires, got a set of Autolite wires & again, one at a time replaced the wires. No change.

With the engine running pulled the tops of each wire off the coil one at a time & each is firing a spark.

What have I overlooked?

Thanks, this is my only vehicle & must get it up & running ASAP.

Same thing happened when i did my plug change a few months ago. Even tho there was no Check Engine Light, i plugged my scanner to the obdII port and it gave me "cylinder 2 misfire". When i pulled that plug out, i noticed i had cracked the ceramic on it. I ended up changing all my plugs again to be certain, as i had cracked 2 of them by over torquing.

Pull your plugs out and see if u have damaged any.

I've learned to go easy on the wrench when I'm tightening spark plugs :rolleyes:

Just got back from Autozone & they read the code P0302 you guess it-misfire cylnder number 2.

I had no torque wrench & really cranked down on them. I bet I cracked one too.

I'll let it cool off & then recheck them tomorrow.

Thanks.

Isn't cylinder # 2 the middle passenger side cylinder?

Sure is. On my 2007, u can easily get to it from the wheel well.

I never used a torque wrench, i just went by feel.

Goodluck! Hopefully I helped you out a bit.

These plugs need not more torque than a little past hand tighten using a socket wrench, but just enough to know they are in.

Nah! just tighten them up till they start to get loose again and then back off 1/4 turn. :lol:

why not just smoke-um in there :lol:

At that point, you will then need the number to the closest tow truck and shop. :lol:

Because that is just too easy. :lol:

Anyhow, back to the main topic... this might seem odd... but did you gap the plugs before putting them in? Or did you just buy plugs and stick them in?

Just what I was thinking. Should be gapped to 0.054".

Plugs were supposed to be gapped & I checked them before installing.


The plan tomorrow is change cylinder #2 with a new .054 gapped plug & see if that helps.

possibly the wires? Autolites and Motorcrafts are two different things and if it isnt the plug, change those out. our ignition systems dont like anything except motorcraft

Looks like the plug was the problem.


Changed it out for a new one & running great now.


Thanks for all the input!

How are those wires? Autolite has several different grades. Did you get the professional series?

I did not change the plug wires.

Have an 02 4.2 v6 that is doing the same thing. So I should pull them all and check for damage?