05mustV6

Newbie here, please bear with me if this is unclear. I did some searching but not sure my rough idle is the same as others mentioned.

I added a JLT Cold air kit and SCT custom tune to my 4.0L The result was a very rough idle with rpms varying from 200 all the way down to 500-600; then stalling out. The throttle was not responsive at all. I returned the car to stock tune and after it warmed up things were back to normal. Cleaned MAF and reloaded tune - nothing changed. I spoke with the company I bought my tuner from... still waiting for a revised tune. The timing of the car seemed off to me.

In my haste to get things back to normal I decided it was time for a tune up. Put new NGK Irridium IX plugs, taylor 8.2mm wires, and screamin deamon coil pack on last week. I reloaded the tune and the rough idle was worse and now the car was back firing.

The gas was low and from last fall still, so I put 15 gallons of 93 in and loaded the 93 tune I had. Worst running yet, backfired like crazy and when I got out the catalytic converter was glowing red. Car sounds like it has a pretty radical cam in it, which it does not.

Here is a bad quality youtube vid of the car running:

Please help me get things started back in the right direction. I am thinking I didn't get a plug seated well; causing the back firing and cat glowing. I plan to check into this first, then possible bad coil pack or wires.

I still have no idea about the rough idle from the tune and CAI - and no response from the company I bought my tuner from....

Car has 63,000 miles, custom dual exhaust, and pretty much stock everything else except appearance mods.

Thanks in advance

edwin108

I would definately check the plugs, maybe one (or more) is not gapped correctly. Does it run like that with the stock coil pack?

05mustV6

This is going to sound really dumb. Please be easy on me.

I had the 1 & 2 plug wires on the wrong posts on the coil pack

I took the time before changing the original coil pack to make a diagram of all wire/cylinder locations..... I got something wrong. Good thing ford marked them on the original coil pack for me.

Still idles a little rough, but I need to reset idle to my tune. Also going to recalibrate my throttle response and give it a test drive soon. The whole front bumper, grille, and lights are off the car right now for some changes, hopefully I can get it back together sometime this week and drive it.

I didn't put the original coil back in because the plugs are gapped to .065 per the screamin demon recommendation. If the idle doesn't flatten out I will re-gap the plugs to .052-.056 and change the coil.

tx_zstang

Dont feel bad; you're not the only one who crossed a wire after changing plugs

There is nothing wrong with the stock coil and using plugs at the stock gap.