mismatched platinum plugs in 97 DOHC

[89Ru]

'97 outback EJ25D, 220k miles (edit: 100k on jdm engine)

guess at around 50k miles since last plug change.

 

Figured it was time to take a look at plugs. Pulled #1 and #3. They are different...

 

#1 PFR6B11

#3 BKR5EGP

 

Not only are the plugs different, note different heat range (#1 has the '6' hotness and has buildup on the ceramic)...they are fairly equally gapped to around 1.4-1.5mm

 

Anyone running mismatched plugs to maybe deal with the wasted spark uneven wear on platinum plugs?

 

When I first bought the car it had misfires that got worse when it was wet and going down hills with no throttle at highway speeds. Haven't had a misfire in a while. #1 plug socket on the coilpack is pretty corroded (carbon arc damage) but the metal contact seems fine.

 

Edit: Misfires may be phantoms...car doesn't stumble, the only way to tell is the CEL.

 

#1 plug has arc damage on the ceramic insulator. This might mean a new set of plug wires or will a dab of dielectric grease help this?

 

BTW it isn't too bad to get these plugs out from underneath with the front end jacked up. For installation I think I'll try feeding them in snugged on a scrap 5/16" fuel line.

 

My owner's manual says to use PFR5B-11. I have a set on hand. I think running hotter plugs will clear the buildup on the #1 plug and may help the misfire issues.

Edited December 16, 2012 by 89Ru

[89Ru]

Well #4 was a pain to get out from underneath.

 

#2 and #4 are both NGK PFR6B-11.

 

#4 gap 1.7mm severely worn center electrode

#2 gap 1.2mm

 

rain tomorrow, have to get this done.

[Speedwagon]

I always go in from the top. Remove the airbox on the pass side. I can usually squeeze past the battery, depending on its size(otherwise you might need to remove it). Also, I use a standard spark plug socket(with the rubber insert) and a small extension(4" I think) to remove/insert the plugs with my fingers doing the turning to start them.

[naru]

I`ve run mismatched (hotter) plugs to combat oil fouling more times than I care to recall.

 

Not sure what you mean by arc damage,but,dielectric grease won`t help.

Sounds more like detonation damage brought on by compression increasing deposits in the engine.

[89Ru]

I`ve run mismatched (hotter) plugs to combat oil fouling more times than I care to recall

 

that could explain it but it doesn't appear to be oil fouled.

 

forgot to mention this is a JDM engine so its probably got 100k on the clock by now. I'm going to replace the plug wires, two of the jackets have nicks but it doesn't look like any burn through.

 

here's a pic, sorry for being confusing about the arcing issue.

top to bottom cylinders are 3,1,2,4. cylinder 1 plug seems to be arcing on the insulator?

 

 

 

[89Ru]

I always go in from the top. Remove the airbox on the pass side. I can usually squeeze past the battery, depending on its size(otherwise you might need to remove it). Also, I use a standard spark plug socket(with the rubber insert) and a small extension(4" I think) to remove/insert the plugs with my fingers doing the turning to start them.

 

I removed the rubber boot in the spark plug socket and taped the bits together. Easy to wiggle down onto the plug and no worries about leaving any bits behind to fish out. Next time I think I'll keep the rubber insert in...left the plug a couple of times when it was almost all the way out (preventing the assembly from being wiggled back into the hole) and then had to untape, disassemble, and then insert pieces and reassemble in the hole...need the hands of a surgeon to do that well rather than my stiff thumbs.

 

spark plug socket --> universal --> 1.5" extension --> driver = 5.7"

just enough the clear the head.

 

One good reason for doing the job from the top. Cold stiff hands drop stuff, no big deal. Dropped wrenches underneath can land on your...face

Edited December 16, 2012 by 89Ru

[Quidam]

That plug for #1 looks like it's cracked. It may be that the resistor is in the top of the plug and the spark is bypassing it, taking the path of least resistance.

 

Doug

[Fairtax4me]

I doubt this was an attempt to combat the effects of wasted spark. Somebody had problems with number 1. Probably cracked or broke so they put A new spark plug in, and didn't bother to match it to the type already in the car.

 

The burn mark is where spark is obviously jumping to ground. This could be due to a crack in the spark plug or a split in the boot. Definitely a good idea to replace the wires. And yes, you should put dielectric grease on all of the boots to help prevent moisture breach and arcing.

 

I would have put a set of BKR6E-11 copper plugs in it. It seems to me that the platinum tips wear more unevenly when used with wasted spark systems, but its just a theory right now. I don't like paying $35 for a set of spark plugs that last no longer than the copper plugs that cost $10.