Spark plug intervals
 

How often are folks changing them? I have NGK, with about 5k miles on them. Totally stock, 12a with an even mix of city stop and go, spirited high reving and highway miles. Been in for 3 years. No real issues, but factory service intervals don't seem appropriate for 30 year old car. It has 65k on the odo. Thanks

Its hard to say, until I switched to RX8 plugs, I would just pull em every few moons and check to make sure they looked good and weren't cracked or damaged. I don't drive the 7 as much as I'd like so FSM service intervals really don't apply.

I ran my last set to 15K, then into storage over the winter. Spring: car would NOT start so I spent a weekend swapping in most every ignition component to get it running - and failed... until, you guessed it, I popped in a new set of plugs. BOOM. Off to the races.
So for me (80 SA) its no more than 10-12K mi a set.


Stu Aull
80GS
AZ

Thanks, looking at them, they have good color, so I'll clean them up and leave them in.

Failures are usually either cracked insulators or burn up electrodes. Usually pretty obvious with visual inspections.

I change mine every two years or 10k miles, whichever comes first.

With my all stock '80, they needed to be replaced every 3000mi, period. They were thoroughly worn out by then. That was a set of 4221s once a month.

A buddy of mine had a set gathering dust that he gave me. Before i tear into the intake oring, water pump etc this weekend, I changed the plugs out. What a difference, not sure which one was bad, but the engine is much smoother at higher revs.

Sometimes its just the act of unplugging the leads and plugging them back in that makes a difference as well. Glad to here its working better.

Yep, definitely check all of your high tension wires while you're at it - including those at the Distributor Cap. I was adding some oil a few weeks back and noticed that the Trailing Coil lead from the Trailing Coil to the top of the Distributor Cap had come off at some point, but was still close enough that it was hard to tell. Tugged on it, and it was completely unattached. Plugged it back in and got a little more power back immediately, and likely better fuel economy, too.

Plugs seem to be fine when I remove them, but I replace them anyway due to age, not mileage. I usually go about 2 yrs, driving about 5k mi a year...

Stupid question, why do the NGK plugs have a screwed on top at the connector? I think that might be why it runs better, since 3 of the 4 were several turns loose. I'm afraid to crank down the new ones as I don't want to crack the porcelain.

The only plugs I've seen with those are my lawn mower 😛

That is so the plugs can be used with both types of ignition cables.

My Audi-engined VW needs plugs with the small diameter threads, which in the 2000s means that the plugs need to have removable ends.

Lots of applications for these plugs... Bosch,NGK,Autolite all have screw on connectors. Some Bosch plugs actually have two types of screw on connectors in box,1 on plug,1 loose in box. Regularly find these screw on tips loose on changeout. Make it a point to hold plug in my hand and tighten tips with pliers and slight twist of plug before installing. Have never seen a plug i've done this too and removed when its service life is over have the tip be loose. I have seen on one occasion when fault tracing driveability/intermittent misfire where one of these screw on tips had unscrewed completely from stem of plug but was still firmly in spark plug wire connector and the two touch each other. I found this by investigating different firing line on cylinder in question while scoping ignition. Removed plug,screwed plug into boot to reattach terminal,tightened with pliers,reinstalled plug and problem went away. I subsequently put a set of fresh plugs in car. This was a 1984 Saab Turbo 900,as i recall,all the other screw on tips were several turns loose.