Tubra

I recently replaced my spark plugs & wires on my 4.0, and the driver's side bank was noticeably more worn than the passenger's side. Is this a sign of a bad coil pack? I do have a minor start issue in the morning. (480 CCA amps reported from the 1.5 yr old "500 CCAamp" Motorcrap Battery. Voltage nominal, New Alternator, and recently checked as well.)

I've been having idling issues as well while in "drive." I've changed the fuel filter, cleaned out the TB obsessively, cleaned the air filter, and MAF, tightened up the TPS clip, boots, etc. I am @ 61k miles and considering seafoaming and making an oil catch can for the PCV line. (The amount of oil in the intake is UNREAL.) The idle dips to about 600rpm from 750rpm when the radiator fan switches on. (more than normal.) The issue remains regardless of stock and customs tunes, and fuel brand.

I am also in the process of repairing the infamous thermostat cover gasket leak and replacing the thermostat for the hell of it. (doesn't look like the housing is cracked.)

I've been researching all this for a few weeks now on this and other forums. I am about at the end of my searching limits and just wanted some fresh eyes and some tips for what I've missed.

Nice Pony

The stock Motorcraft Platinum sparkplugs are total crap! I pulled mine at 30,000 miles and the gaps were all over the place not to mention they were just very worn out. I have been running Autolite 5143 Copper Core spark plugs ever since and they always look great with nice even wear and just really need a slight regap. I now have 128,000 miles with no sparkplug related issues since changing.

tx_zstang

I ran into the same issue with the stock Ford plugs, on driver side as well. At about 25k miles, they were wore out like yours. Was using the stock coil and wires as well.

Replaced the plugs (wth ngk TR6 plugs, 1 heat-range colder, for blower applications), and 9mm plug wires. Had nor issues with the plugs after 15k miles, no signs of wear.

I contribute the custom tune and 93 octane to part of the problem, plus the driver-side wires are shorter in length. With a totally stock vehicle, you might not have the issue.

...and that's why your car is running a little rough...those driver-side plugs!!!

muzzy

Ngk tr6 @.035 and retune your car.......