Bosshogoutlaw

So it getting cold out so i decide to get my friend to help me install my new spark plugs & wires on my 2005 v6 stang. I went with the NGK 7159 TR55-1GP Single Platinum Spark Plug & the taylor street thunder 8mm spark plug wires. Everything went well besides three things that concerns me. For one we didn't use any anti seize nor any dielectric grease on the spark plugs & wires because my friend said it ngk didn't call for it. After i left his house out i notice my car dropping in rpm from 750 to 500 rpm while stopped at the light but is sounds like its gonna shut off on me or something. Also Im hearing a weird bumping noise coming from the muffler. But while Im driving its fantastic. I notice a improvement in throttle response it just when im idling that really has me concerned. Oh & also we didn't space the new spark plugs either but where gonna do so tomorrow to .65. So plz ANY insight would be great

audioAl

Ford's don't like change in plugs, any mechanic can attest to that, that said NGK is a great performance plug. Hopefully gapping them and a little grease on the threads will fix your rough idle. The grease will help you get them out the next change. I'm searching for the right NGK plugs for my 3.7 motor soon.

JJHoover

always put anti seize, also it is possible that some of the plugs were not tightened all the way

Nuke

I suggest going back to the OE COPs and see if the rough idle and "thump" (which could be a low idle miss) goes away. The OE COPs are pretty decent IMO and aftermarket COPs have had their share of issues.

GrayPony

@Nuke.. no COP's on the 4.0
@OP Make sure you have the plugs/coil wired in the correct order.

IvanRad

Id check all the sparks . Make sure the wires were used properly . I think they were different lengths for a reason . Check to make sure everything is snug tight . Change your fuel filter if need be . Then I'd look into your electrical. Right now I have a slight rattle at a stop sign in drive . It's either my tranny mounts or my trannys going out. Alternators are known to act funky especially the oe one . Might need a swap

Bosshogoutlaw

@GrayPony I took the wires out one by one so we wouldn't get them confused so that's not a issue

@JJHoover soon has i get a chance were going to check that later on today

@IvanRad I was contemplating the same thing early this morning while i was driving to work but i also was thinking that the car might have to relearn idle since the "Taylor Street Thunder" are a low resistance wire than the OE.

Nuke

I was wondering about that as I typed it. My wife has her 4.0 with her at work and I never really took notice before.

I'd still change back to the OE wires just to eliminate that from the list of possibilities. Although it seems like an unlikely coincidence, I'd clean the TB and check to see if the fuel filter has been replaced within the last 30k miles.

DenIs2Fast4U

I have NGK Iridiums and the Taylor 8mm wires and they have been great for me. Put them on at 65,000 miles, now have 72,000, idles perfectly smooth and response is great.

I would suggest you gap to the OE specs of .052-.056, personally i always go to the middle of the range so I gap .054 here. .065 is way big. And definitly use dielectric tune-up grease it will help with the conductivity.

Gapping them is always a must IMO even if they say pre-gapped from the manufacture. I always seem to have to adjust them slightly.

And yes use some anti-seize on the threads

After doing these things I would be supprised if it doesn't help your situation

Bosshogoutlaw

Its been raining for the past few day so I haven't been under the hood yet. But last night when I got off work I made the stang relearn idle...ac max while idling for five minutes ac off while idling for five min then I drove ten miles on the highway. I drove home park the car an got up the next morning with a check engine light on. I never been so happy to see it in my life lol. Took it to advance auto to diagnose an what do they find? Mis fire cylinder 4...FINALLY I can drive with peace at mind again