How long are NGK plug wires for Miatas lasting these days?

What’s the current lifespan of NGK plug wires for an NA Miata? What’s everyone else finding? 

Asking for a friend, of course. 

I've bought (and sold) many NA's running strong on what appeared to be the original NGK's. Most had 60-90k. 

That being said, the Toyota COPs are a very cheap upgrade. $12 at the junkyard yesterday got me 6 COPs off an IS250

In reply to calteg :

Don't you have to find a way to reduce dwell (or use a standalone) to drive these COPs without burning them out in an NA?

And has anyone shown that they actually work better?

I've had good luck with NGKs overall. Early Miatas were notorious for burning up their original plug wires, and NGK pretty much solved the problem. I've been running Magnecor on most of my cars recently for what is a fairly predictable reason. Lifetime warranty with very few claims.

In reply to BoxheadTim :

Ideally yes, though multiple people (myself included) have run them on a stock ECU with no issues. Currently I'm running Megasquirt 2. If you burn them out, again, $2 each at any junkyard in America.

In reply to Keith Tanner :

I don't believe there is much performance benefit unless you're running ridiculous boost. I just got sick of blowing up OEM coil packs every time I compression tested a motor. I'd pull the wires, remove the fuse, and it was 50/50 whether the coil packs would survive or not. I remember replacements being in the $100 each range. Then you get to jam your hand between the back of the head and the firewall to uninstall/reinstall. Or switch to coil-on-plug and replacement is one easily accessible bolt

In reply to calteg :

Good reason for a change. I've never understood them to have any benefit over stock even at high boost, but if you keep blowing up stock ones then you might as well make it a cheap habit. I don't think I've ever popped a coil while doing a compression test, but I don't do them all that often. It certainly would be good to have a more reliable option than the 1999-00 coils.

The reason I ask:

When we pulled the Garage Rescue Miata from its auto cocoon 2+ years ago, we replaced the plug wires with fresh ones from NGK.

All been good until driving to Orlando the other evening–so figure one hour at close to 4500 rpm. Car was fine on the highway but had a miss once in downtown and stalled. Had a miss after starting up.

Did the obligatory spark plug wire wiggle while looking under the hood. Once cooled down, no more miss. Car ran perfectly all the way home. Car ran fine during a second highway trip the following night. Plugs look good, fuel pump is also 2 years old. The car always gets good gas. 

So, just wondering. Random, isolated incident or are people having trouble with them?

In my experience, the wires don't come back :) More likely it's something else like a sick coil. By running on the highway and then dropping into traffic, you would have thrown a bunch of heat into the engine bay. I'd also check the CAS wiring with a wiggle test as it can fatigue and cause an internal intermittent connection. 

Remember that if you lose one coil/wire on an NA Miata, you lose two cylinders. Makes for quite the rough running.

In reply to Keith Tanner :

The engine sounded rough but not that rough. But they are 31 years old, too. Do you have a preferred brand for coil pack replacement? 

And I’ll check CAS wiring, too.

Thanks. 

In reply to David S. Wallens :

I would use my Mazda Team Support membership to get OE parts :) But if it wasn't down to two cylinders, I wouldn't be swapping coils yet. To take out one cylinder, I'd be looking at the injectors and their wiring. They're batched, but unlike the wires losing one injector won't take out its twin. I can't recall if there's a CAS failure mode that will drop a cylinder.

To identify if it's a coil or wires, next time it happens pull the #1 wire. Then plug it back in and try the #2. If one of those makes no difference to how the car runs, look at the ignition parts. If the car is affected by both, it's not coils/wires.

Or plug in a laptop running Data Log Lab and look at what the Link tells you. 

I cannot speak for Miatas specifically, but two ended coils can very much fail only one cylinder, if the coil arcs to ground internally.  Likewise a spark plug wire that arcs through the boot or the wire insulation will only drop one cylinder.

Keith Tanner said:

In reply to David S. Wallens :

I would use my Mazda Team Support membership to get OE parts :) But if it wasn't down to two cylinders, I wouldn't be swapping coils yet. To take out one cylinder, I'd be looking at the injectors and their wiring. They're batched, but unlike the wires losing one injector won't take out its twin. I can't recall if there's a CAS failure mode that will drop a cylinder.

To identify if it's a coil or wires, next time it happens pull the #1 wire. Then plug it back in and try the #2. If one of those makes no difference to how the car runs, look at the ignition parts. If the car is affected by both, it's not coils/wires.

Or plug in a laptop running Data Log Lab and look at what the Link tells you. 

Thanks. We’ll see what I find this weekend.

In reply to Pete. (l33t FS) :

Fair point. Try watching it run in the dark, that'll spot a grounding wire :)

My money is on the CAS wiring

Little water misting in the dark will help. Also seen spark plugs crack and cause intermittent issues like this. 

Paul_VR6 (Forum Supporter) said:

Little water misting in the dark will help. Also seen spark plugs crack and cause intermittent issues like this. 

Hey, that’s a Carl trick, too.

I had a similar situation after replacing coil pack (OEM). A plug wire (NGK) had worked loose in the coil pack. 

Engine is still purring as usual. 

Wiggling the CAS wiring doesn’t change anything. Cleaned the involved connectors with some CRC electrical contact cleaner just because. 

Did close to two hours on the highway this weekend–a there and back–and no issues at all. Hmmmm.

Oh, hang on. This is a Link, and it's got some years on it. They would occasionally have trouble with cracking solder joints on things like connector headers. I'd pull it out and reflow any that look sketchy, especially on the injector drivers and the header.

In reply to Keith Tanner :

Hmmmmm. Thanks for the heads-up and, yes, it’s running a FM/Link circa 1999.

And photo of CRC’s electronic cleaner because. (I use it on my guitar equipment, too.)