In anticipation of getting my car tuned for my Zex wet kit I put in a set of the Autolite HT0 plugs (one step colder than stock) and when i fired the car up it ran rough. It did not sound like it was missing it was just fluctiating in RPMs from 600 to 1500 or so up and down odly. It would rev up fine and after a few minutes it died. I fired it up again and it was still doing it and it finally gave me a DTC for lean on bank 1. So i swapped out the plugs on that side with the stockers and fired it back up and averything ran fine. So once again i re-swaped back in the HT0s and fired it up and it ran fine. Took it to get it tuned and made it though several passes and when i went to fire it up after the last one it started its rough idle again. We pulled it off the dyno and then started once more and once again it was running fine. Been running fine for a day or so then on the way to work it died on me in the parking light, it fired back up fine and seemed to be running fine.

Ever since i put the plugs in ive been running scared with the radio and air off so i can listen to the car, i may be getting paranoid but what i notice is idle is around 600rpms once its warmed up which i think is about normal possibly a little low?, but when im driving and let off the gas and slow down i notice the rpms go down like normal once they dip below 1000 the raise up for a second, maybe a couple hundred rpm, before finally falling back down to 600ish, it may have always done this and i just didn't pay any attention.


Anybody with a little insight would be appreciated.

 

Didnt think you needed different plugs with nitrous, just with blowers.

 

If you want to run safely with the 100 shot or more its recomended

 

See if you get a tuner to compensate for the plugs with your SCT, they are affecting the 02 sensor readings.

 

Did you properly gap the plugs before you installed them?

 

I thought these plugs were made for our cars and didint fit on any others. Plus these arent ordinary plugs how do i go about gapping these?

 

These plugs do come gapped at .045", but you should always check the gap. I can get closed due to being bumped around in shipping, you can hit it on the head or threads etc when installing etc... I know I saw a tool for those plugs but I can't put my finger on it at the momet.. I keep looking for ya, but I am sure you can get one of the older style feeler gauges to work with it. Ther not as nasty as the 4 electrode plugs

 

The plugs fit various modular engines, including the F-150, etc.

You can gap them by squeezing them in a vise using a socket to support the plug. Ford makes a special gapping tool, and there are various vendors that make inexpensive clones of the Ford tool. Piedmont Modular Performance (PMP) has a nice one that is easy to use.

 

http://www.pmpparts.com/index.php?ma...products_id=34

Sparkplug gapping tool.

 

A 600 RPM Idle is low.

Manual Tranny is typically 750RPM and Auto's idle around 800-850. Not sure of the new drive by wire systems in the newer stangs but the bouncing revs your mentioned can be created by a couple of things in 04 and older stangs. Intake leak (as in CAI or manifold) and/or sticking TPS.

Definitely check the gap of the new plugs. The new stangs seem to very fickle on simple things.