Changed plugs, wires, air filter, fuel filter, were on the 3rd used idle air control valve and the RPM's still jumping. Now my mechanic wants to try changing the throttle body. Heres a . What do y'all think?

 

Does the CEL come on and go off when the key is turned to on? Or just go have a parts store confirm there are not codes, most parts stores outside of the country of CA will do this for free.

Next, be sure the hoses to the IAC are clear and flowing. Then be sure to properly bleed the air from the cooling system.

These are just some "starter" points. There is much more we can get into if these test out.

 

mass air flow sensor been checked? normally when they are bad rpms jump around a lot

 

You do realize/know the 98 4 cyl's do not have a mass air flow sensor?

 

Its just a vacuum leak. Find leak. Fix leak. Dont waste money replacing parts.

 

I don't know about 98, but my 92 has an IACV (Idle Air Control Valve) and an EACV, also known as the electric idle control on my trouble code list. (Code 14) On my car it's on the back of the intake manifold, with 2 small coolant hoses and a 2 wire plug. May be as simple as your throttle cable being too tight, but I kinda doubt it. A check engine code would help