This is not Miata specific, but just a general question on COPS setups.

My DD has factory COPS. It's a 6 cylinder (3.7L) Jeep Liberty. I recently changed the plugs as routine maintence at about 60K miles. Those plugs (NOT* original, by the look) were absolutely shot. As in gap so large that I was surprised the damn thing ran. Electrodes were very worn, and all were worn off at an angle of about 60 degrees to the centerline, as well as rounded off all around.

The thing didn't run rough, and changing the plugs made very little difference, except that mileage improved by 20%. The Jeep has done very little towing or off-roading. So, is this normal wear for a COP setup, or is it just a case of crappy factory plugs?



Edit: NOT the originals, as I had earlier mis-stated. They were cheap Autolites, new ones are Bosch.

 

And to think these new cars aren't scheduled for plugs 'till 100k....
--Alex

 

Not so far as I can tell, three out of four of my cars are COP.

4, 6, and 8 cylinder engines. They all run great with the exception of the 4, but that's more my fault than the car's.

 

I was just surprised at how worn they were. I bought the Jeep used, with about 30K on it, and they claimed it had a "full tune up". I suppose they could have just been giving me a load of B.S.

But even if they were original, 60K shouldn't mean plugs are that far gone. Looking at them, you'd think they'd been in there for at least double that mileage. As I was doing mine, I was helping a buddy change his in a '04 Impala (what a huge pain in the ***!), and at 40K they looked nearly new.

 

Were they the correct plugs for that motor?

Or is it possible that the gas run through that vehicle was poor?


IMO, both of those could affect wear regardless of the type of ignition.

 

I've had plenty of coil over plug equipped cars and no problems with the plugs...they all used NGK plugs though which are pretty good plugs.