kball

Yep, Durk is the diag king of this thread. He hit the nail on the head! I'm just glad the OP didn't get flamed for using those plugs.

TheDurk

Thanks for that and, yep, nice job on the gentle approach kball. Others have indeed been beat up for that. Although, in theory, the dual grounds are required only because of longevity issues, not because they don't work out of the box. (The waste spark system fires twice as often, so two electrodes compensate for the added wear. Only one electrode fires at a time so the duals last twice as long.)

The truth may be that the cars are just allergic to anything that is not the OEM Denso or NGK plugs. Personally, I have stuck to the NGK's from NAPA for eleven years and never had a problem. However, in this case, I think we are looking at a case where the plug was just a dud right out of the box--which was what I suspected when I made my first post in this thread.

The black trail is a spark track, where the voltage goes around the insulator instead of through the core electrode. This could be due to an open internally in a faulty Autolite plug, so the spark takes the path of next least resistance to ground which is outside the cylinder. This is equivalent to major overgapping, as far as the other plug is concerned, so as it is a series circuit, spark energy in the other cylinder is also compromised.

If you still have the plug in the picture, it might be fun to measure the resistance from the top center to the bottom center--I bet it's a lot higher than the other ones you took out. If so, save the old coil, it was probably good--its spark was just going to the wrong place. (If there were anyway to look at the plug while operating, you would have seen blue spark lines going down the outside of the plug.)

Left untreated, this condition could have destroyed the OP's cat. Thanks, Autolite.

gdutch

I keep hearing everyone swear by Denso and NGKs, but I've used Bosch Platinum +4s in my 4Runner since I bought it (and both cars I owned before it). Just replaced the plugs last week after ~35k on them, and they were perfect. I did have misfires when I first bought it but that was due to a bad coil pack. Once it was replaced I've never had any problems. Just my .02.

brian2sun

It's not how many people the Bosches (or single electrode plugs in general) have worked well for - there are several people like gdutch that don't have any problems running them. Instead, it's about how many people the Bosches do not work well for. It's like a hit or miss thing and you never know if your engine will like them as much as the next guy's 3.4.

Here's how I see it: There's a sticker on the engine block that warns not to use anything but dual electrode plugs. In my mind, that alone should be enough to tell you that there's a good chance that anything other than dual electrodes won't do well. I personally have no idea why people insist on going against the advice of the manufacturer and engineers that designed the engine, but hey, you only live once so here's to rebellion! Secondly, knowing that people have tried them and failed again and again, why would you want to take a chance when NGKs and Densos have a near 100% success rate? Here's a pic of an old Bosch out of my 3.4 from years ago (before I realized not to use them) - Note: This plug had less than a year/12K on it and I've never had another one look like this again:

gdutch

Yeah, obviously you need a multiple-ground plug; the Bosch +4's that I use have 4 nodes. If somebody is using a single ground plug, whatever the brand, they're asking for trouble. So, the problem is not in the brand, it's the design of the plug itself.

RTFM.

Rosko24

So if I just replaced plugs with a single ground would you suggest I pull those and put in double!? I'm having the same issue you were having and it didn't fix it! Also if you could include everything you try to fix this issue!

vasinvictor

iTrader: (3)

So this is a 5 year old thread, but single electrode works just fine. Been using single electrode copper BKR series for 30k and are about $2/plug.. You gotta replace them more often, they don't last as long as dual electrode. If you're having problems it's something else. Failing crank sensor will cause misfire and usually not throw a CEL. Mist wires at night and check for arcing. Check your grounds to see if they're tight.