ryan_89_mustang

Whenever I start the stang with a cold engine, It instantly idles to 1k and stays there but say I turn it off then right back on it surges from like 600 to 1k for several seconds and catchs a idle.

And I have a seperate question, I am looking into a autometer temp guage what comes with them do I have to tap a hole in the firewall to get the temp sensor on the lower intake? or do i tap into an exsisting wire?

AdderMk2

its supposed to idle high... thats what your IAC is for...

leave it alone, there is nothing wrong

ryan_89_mustang

I understand is is supposed to idle high on startup but why does it struggle to catch an idle on a warm engine only

AdderMk2

because you have a surging problem.

do an idle relearn and you should be all set (you probably have a vac leak too)

lxman1

Check you TPS idle voltage. They will surge if it too high. Shoot for around .95V.
If the temp gauge is mechanical with the metal line, then it must go thru the firewall. I ran mine thru the accelerator cable grommet and sealed it with RTV sealer.
If it is electric, you must run a separate wire and use the provided sending unit calibrated for that gauge. The stock one will not read correctly.