Autolite AR-51s causing poor idle/cruise?

[trbowgn]

Last night I changed my plugs from Champion RN9YCs to Autolite AR-51s and this morning on the way into work the car felt like it was dropping a cylinder at cruise (50mph) and also at idle. I stopped and checked all my plug wires and they were fine.
It has always idled a little rough but the cruise is a new one.
Has any one else had similar issues with these plugs?

[Nemesismachine]

I thought this was a gun thread. My bad.

[GLHNSLHT2]

I run them in all my TD's. Even my g/f's jeep libby (AR's in her application) The idle is better than with stock plugs. I've even taken my used AR51's out of my daytona and put them in a buddies TD that had brand spanking new champ's and the idle was noticably better and it revved up quicker. You didn't crack the porcelin (can't spell that tonight) putting them did you?

[rare_ram]

Gapped correctly?

[tsiconquest88]

thats funny, i just switched to 51's as well and they were great it seemed the first day and past couple days feels the same way you speak of, i gapped mine to stock gap for the r9n's though, maybe i have the wrong gap for using toward the 51's??

[boost geek]

I run AR51's without issues. Are they too cold for your application?

[tsiconquest88]

possibly, but i was using cold ngk plugs. (bp8es) i seen a thread recently where glhnslht2 said they were good even for stock app's so i figured i would give it a whirl and i was lovin them till yeserday and today where i was experiencing what the poster of this thread mentioned. COULD happen to just be something else, in mine and even maybe his and not the plugs at all, but i was fine till yesterday, see what happens, no biggy.

[OmniLuvr]

i always suspect injectors, i would do a cyl balance test to figure out the culprit cyl, then swap injectors around, and see how it goes. you can do the same with the plugs, but i think its injectors, ive had way to many probs with them...

and im runnin 51's with no problems in multiple vehicles.

[GLHNSLHT2]

My new yorker runs them and it's stock other than a ported exhaust manny, S60 turbo and 3" exhaust.

[trbowgn]

stopped and picked up a new set of RN9YCs today after work put them in in the parking lot and fixed the problem.
Looked over the plugs very closely and saw no signs of cracked plug, that is what i suspected.
With the Champions it runs nice and smooth.

[GLHNSLHT2]

weird

[amcpacer]

That is strange. I have tried many different brands of plugs included the frowned upon bosch platinum. Every plug made the car run exactly the same with no change in fuel economy or power. Perhaps one of the AR-51 plugs you bought had an internal crack that allowed arc to occur in the insulator stem instead of at the tip.

[trbowgn]

That is strange. I have tried many different brands of plugs included the frowned upon bosch platinum. Every plug made the car run exactly the same with no change in fuel economy or power. Perhaps one of the AR-51 plugs you bought had an internal crack that allowed arc to occur in the insulator stem instead of at the tip.

Thats the only thing I can think of, I will put them under the magnifier when I get a chance and see whats up but now it is Saturday and time to go work on the boats ignition issues.

[tsiconquest88]

yea it could definately be a defect or something, afterall the things dont sell off the stores like hot cakes and they probably sit there, get drop now and again, who knows lol. those little boxes they are in dont absorb shock thats for sure. I know the set of 4 i bought was the only set of 4 in a 50 mile radius and they said they been there for a long time haha.