high idle in park

98 trans sport 3.4

idles up to 3k in park, and sometimes 1500 in gear. sometimes it doesn't idle high at all. assuming it's a sensor, should i start with the tps or iac? thanks in advance

98 trans sport 3.4

idles up to 3k in park, and sometimes 1500 in gear. sometimes it doesn't idle high at all. assuming it's a sensor, should i start with the tps or iac? thanks in advance

I would do the TPS first. Are there any codes set?

Start with a visual inspection.
1) clean the TPS and IAC controls, electrical connectors, and use dieletric grease for connector electrical connections.
2) Consider a smoke test done for unmeterd air leaks, because she's running lean.

Suspect - Bad plastic, rubber, or seals from the EGR, or PCV system.

already replaced pcv valve and elbow because they were cracked. engine light isn't on, i might be blindly assuming the light works. is there a self-diagnostic procedure on this? i will clean the connectors first, thanks for the tip