SP542 Thread

I picked up a set of 6 sp542 and 6 sp534. I put the 534s in this time. It runs so well with the 93prx I couldn’t bring myself to switch them up? I’m not sure what the best gap would be to run them at either. Any opinions?

Spartan1 said:

I picked up a set of 6 sp542 and 6 sp534. I put the 534s in this time. It runs so well with the 93prx I couldn’t bring myself to switch them up? I’m not sure what the best gap would be to run them at either. Any opinions?

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I'm sure there are several opinions, but I recommend 0.030". Also, could you use your handy multimeter (of course you have one, right?) and measure the resistance on the SP534s from the tip of the center electrode to the wire terminal at the other end? It will be in the K (thousand) ohms range. Also verify that they are the "iridium" plugs and have the obvious pad on the underside of the ground electrode right above the center electrode gap.

FYI - O'Reillys has the SP542 for $5.99 each.

So can anyone think of any cons of trying this? Just decreased life span if anything, right?

Wonder if it has to do with this old thread: http://www.fordraptorforum.com/f260/ford-changed-spark-plug-part-number-56220/

In forced induction motors, running a plug one or two steps colder than stock reduces pinging/detonation, especially if the motor is tuned or squeezed.

Well I installed the SP542's today. Truck has just under 4k miles, so barely broken in I have noticed a stumbley idle at times, nothing major though. I guess I'll see how these fare and report back. I left the engine cover off - all I can see that it does is retain heat. Anyway, I'll post back once I have some miles on the new plugs.

never done an engine mod but have the plugs ready... any advice... really simple right? couldn't find a video gotta learn some how...

I see this thread came back after 2 months of no activity. Did any of the early skeptics finally install them? If so, please provide your thoughts.

I am getting ready to do an MPT 93 PRX with FR IC and 170 t-stat install on my 2018. I ordered the SP-542s based on this thread, even though I have had zero issues with my factory setup after 2K miles.

Well, I can say that the plugs do smooth out idle for sure. Actually, all around the power band seems smoother - the truck seems a bit more willing to get up and go. Worth the price of admission IMO.

I just swapped mine out at 22,000 miles because of this thread. Did it make a difference...MEH. Sport mode may have smoother shifts at lower RPMs now. Guess mine was good out of the box. Been running 93PRX for past 17-18K miles. Truck has always run great.