Spark plug life expectancy
 

My M103 has been stumbling a bit when starting cold. It's been about 30,000 miles since I changed them for other reasons (valve guide seal change) and I got to thinking about the spark plugs. So my question is, is it about time to R&R them?

Cap & Rotor? And if they're not that old but look bad, then your coil?

Maybe I'm paranoid, but I just went through this and shortly thereafter my coil failed, stranding me ('88 300TE, 177k miles, maintained fastidiously)

Anybody?
 

So what is the recommended or suggested replacement interval for spark plugs.

With plat. Bosch says 100k I think, but I do mine with every fuel filter change about 15-20k.

60k is the interval in your Owner's Manual. I stick to that interval.

Jim:

The Bosch H9DC/H9DCO plugs that your engine uses are relatively inexpensive. I change mine annually, irregardless of mileage. Plug condition is somewhat an indicator of what's going on inside your engine. An annual change gives you an opportunity to see how things are.

I replace mine every 15k miles. The plugs start to show significant wear around 30k miles. I would recommend no more than 30k on a set of plugs. :)

I agree with Mike that the plugs are relatively inexpensive. I change them every alternate service.