98 explorer eratic idle no w/no engine light

hello all,
i have 98 explorer sport the idle is like surging i replaced the plugs.
sometimes it dies if i put in gear to fast.it jumps from about 700 rpms
up to 1000 rpms.

Sounds like a mass air sensor. It's in the snorkel tube that connects the air filter box to the fuel injector. Common failure, really a maintenance item.
A competent mechanic can quickly get a service code on it and replace it. It's also easy to replace yourself.

Check your idler(?) vacuum tube. Its located on the top-right of the engine. A loose vacuum tube will cause a jumping and unstable idle without seizure.