Hi,

A little bit of history:
Changed the Injectors (need to pass emissions and my CO was way too high in idle as well as surging and stalling occasionally)
Renewed all the Gaskets which were involved
Cleaned what was possible (the Intake was filthy as hell)
Finally managed to get rid of my (hopefully) last Vacuum Leak (The interior fan controls work for the first time since forever )

Result: Car still ran like crap

After three times of re-setting the idle and after changing the IAC two times it finally idles "ok" (only the slightest of vibration, revs nicely etc) --> What I don't understand is why my idle in "park" won't stay at higher rpm's than in "drive", they are only apart maybe 50 rpm's after a few seconds (drive at around 600, park at around 650, but at least not surging like crazy like in the past)
Does someone have an idea what the issue could be? It's not like it seems to be a huge issue, but it should behave differently, correct?

I still have a small exhaust leak somewhere (you can hear it clicking ever so slightly but I don't think its the rockers) --> that should not have any influence on idle though?
+ I still need to check the ignition, whoever designed these damned check marks...they are really hard to see/read

 

That small change in idle rpm between Park (no load) and in Drive is about right.. There is a small hydraulic coupling load on the engine thru the torque converter when idling in drive. This is normal.

 

Cool, I thought the difference should be way higher like 800 vs 600, then I'm glad it's working as designed, thanks

 

Depending upon coolant temperature, run time, ans a few other variables, the idle in Park will be higher. It wiull also be higher in Drive, but since it is skewed up and down in IAC steps rather than RPM, the net difference between Park and Drive idle will be greater.