Question: High idle when in gear at normal temp

[Mike74]

High idle when in gear under normal temp on my 94 Lt1 auto trans but if I put it in neutral rpm goes down. I already put a new IAC and cleaned my throttle I also reset the PCM. I did also checked my EGR by unplugging the vacuum hose and it seems ok(not stuck). No vacuum leak my rpm is 700 when in park or neutral. Is it my torque converter lock switch is bad? Tnx guys.

 

[Kevo]

You need access to a scanner to check TPS voltage along with input switches that might cause ECM to increase idle speed. TCC switch is unlikely cause.

 

[Mike74]

High rpm when in gear

Tnx kevo I will definitely do that but right now I try to unplug my IAC harness and I noticed that the rpm went back to normal when in gear but my check engine light came on. I replaced my IAC last year but I put after market valve and did the resetting procedure. Is it my ECM commanding my IAC to open? What causes that? Tnx.

 

[Kevo]

If the idle corrected as you wiggled connector to disconnect IAC. I would check the connector for spread terminals or broken wire causing intermitent contact. You could rebuild or replace connector if you are in doubt.