88 cavalier z24 2.8 no codes, recent tune up with delco plugs, taylor wires, new fuel filter, cleaned throttle body. two months ago about 2500 miles ago
well now occasionally after putting into park after driving, idle will fluctuate from 600 to 1500. up and down like someone is tapping on the throttle pedal. and also on occasion (three times total) pulled up to a parking space and the car stumbled and stalled.

i'm totally lost on where to go next. cleaned the IAC, checked the MAP sensor (good), did an idle relearn. all to no avail.

Just a suggestion but I would ask questions with your 2nd gen in the 2nd gen forum from now on.It will get more traffic from those more fluent with these older jbody rides.Now to answer the issue I am laying odds it is probably your TCC switch better know as the torque convertor control (or switch) is probably done.In short the problems it presents are car stalling or bucking going into gear or coming to a stop.Sometimes the idle will be a part of the issue as the transmission is not shifting correctly and can cause delays in the idle to adjust.The simple side is to replace the said part and drain and replace your transmission fluid and filter as just replacing the TCC will only burn up the new part with old worn fluid which has lost it's ability to prevent wear and heat build up.I could go look up the part as it is either listed in the sensor section OR under transmission parts on most sites.I am super tired and if you have not researched this I can and will post the part you need weds when I am not worn out.IF this is not the problem after the fact being you have not changed the fluid in a long time and or it could be the switch has just gone bad due to time as this happens even with fluid changes next.I would disconnect the vacumm line going to the EGR and see if the problem goes away,if not remove the egr and clean the carbon out using brake cleaner and try again.This part is sealed and the rubber diaphrams inside might be loosing vacumm and cause your idle to bounce all over the place.I would start with the TCC and just unhook it as it has a two plug harness and will not harm the car aside from a touch less mpg and is mounted on the transmission of course.I hope this gives some insight and will follow up weds with the part # for your ride if you do not find it first.

http://shop.advanceautoparts.com/p/pro-king-automatic-transmission-solenoid-52-0210/5150213-P?navigationPath=L1*14925%7CL2*15047%7CL3*16272 This should be the correct low cost item you need.I want dig into the issue more like recommending checking the tps and or other items just yet.I was a touch rusty looking this up as the freaking auto sites keep changing the catergories to locate this item! It initially was listed in the switches,sensor but they know show this in the auto trans area and doing a search you would be spinning your wheels trying to find this item.