Info required on Autolite AR5 S spark plugs

[Rossco]

Kia Ora all

This question has probably ben asked previously ?
I had an engine missfire and replaced the spark plugs with new Autolite 2245, and it is running a whole lot better!
The spark plugs I took out are near new Autolite AR5 S which the previous owner installed just prior to me purchasing the vehicle!
Are these the wrong plugs for an M151 and could they be the reason for the missfire?

Rossco

[rickf]

They are one heat range colder than the Autolite 2245, and they are Motorcraft AR5 S, not Autolite. The Autolite number for that same plug is a 2243. Motorcraft was a Ford brand and Autolite was primarily used by Ford but was sold for general use, I used Autolites for racing in my Chevy engines when the Champions let me down.

https://www.sparkplug-crossreference.co ... FT_PN/AR5S

I don't think they would have caused to much issue in the way it ran depending on how the plugs looked. Were they fouling?

[Rossco]

Thanks Rick

Sorry my mistake, yes Motorcraft ,I should have taken more care with my description.
They were new plugs installed a couple of weeks prior to my purchase and have been sitting idle in the motor for 18 months now while I rebuilt the bodywork etc.
They looked okay but obviously they require cleaning, the new 2245's were a noticeable improvement as far as smooth running..

Regards
Rossco