Rough idle after warmed up

Newbie - 1991 VR4 - Rough idle after warms up, stalls. Is there a servo motor for idle control? Is it available anywhere? Thank you for any help.

 

A little more detail would get you further.

 

My 91 VR4, in black, is badged 1414/2000. When starting cold, all systems check. Its fast idle (auto-choke? enrichener?) is smooth and after a couple of minutes it drives away easily in all of its awesomeness /ubbthreads/images/graemlins/smile.gif. After 5 or 10 mins of driving however, when pulling up to a traffic stop for example, if I don't stay with my foot slightly pressing the accelerator it will not idle. Before it stalls the RPMs will bounce up and down from coughing-up-about-to-stall to about 1200 rpm. It will bounce like that two or three times and then it stalls. It almost feels like the ignition has been cut, but as RPMs quickly drop it picks up again, bouncing up and down on the idle rev range.
I do try and keep the car from stalling by controlling the acceleration when stopping but it is quite annoying and I am afraid I may be doing further damage. Someone mentioned to me that this car may have a dedicated servo for idle control? I will be picking up a service manual next week but until then I am clueless. Thanks again for any suggestions.

 

[seizer]

Sounds like you may have a possible vacuum leak or something. I would try doing a throttle body cleaning and replace any worn gaskets and do a boost leak test and reset the BISS try looking in vfaq.com and wait for another response from another member.

 

I second the boost leak. Preform a boost/vacuum leak test. Make sure you use the vfaq when setting the BISS after leaks are fixed. If your still running factory IC piping, there prone to leak. Things are alot easier to understand when more info's given. Keep us posted.

 

[flag24]

One of the coils in the isc is open. Test for same and/or replace isc with known good isc. Ben there done that.