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.