daytonablackZ28

i recently got my paws on an all original 76k mile 1996 black on grey auto cherry Z28. after replacing the original Mass Air Meter, the motor now suddenly drops to near 200 rpm for a few seconds after a cold start and stumbles a bit before smoothing out and then runs perfect, all in open loop operation. im not sure if the IAC pintle is sticking when its cold since the problem is most severe when the car sits for a while such as overnight. when the car warms up, its not very noticable if at all. i have yet to start digging into the motor to diagnose. before i added the new mass air sensor, this never was an issue. im totally confused. i still have the original mass air flow sensor which i am considering putting back on just because it turns out a had a major vacuum leak after the mass air sensor which caused me to suspect the maf. i do have a scan tool as well an i was getting intermitent mass air flow code. every thing on this car is probably original considering im the second owner and the previous owner bought the car new at a chevy dealer 20 miles away back in 1996 according to the original window sticker and the first owners registration i found behind the glove box

bw_hunter

Run a scan looking at the coolant temp sensor output. If the computer thinks its warmed up it might lean out the mixture too soon. If you get a really odd reading, check to see if the cts is unplugged or the wire is damaged...

daytonablackZ28

unfortunatly i have a really basic scan tool only reading my coolant temps in real time in degrees F. its amost as if the pintle on the idle air motor is stuck for a few seconds causing the air not getting let into the motor but only at initial start up. its much much worse starting the car first thing in the morning after sitting. i ust replaced the MAF simply because i was getting a code. now im suspecting a vacuum leak after the MAF sensor. its weird why its fine and runs perfect after the car starts and even in traffic etc.

bw_hunter

Perhaps you knocked the plug out if the CTS when working on the MAF. Maybe not. If you are convinced it's the IAC you should satisfy yourself on that first.

Chimera96

might want to put the MAF you took off back on....and see if your problem goes away (because the "new" MAF may be defective).

if problem still is there than check wiring and Ohms of the temp sensor on front of water pump

if you suspect the IAC than take it out and clean it and the orifice. do not push/pull on the end of it

Injuneer

You mentioned you had a major vacuum leak after the (old?) MAF. Where was that leak specifically? Was the rubber elbow torn (air leak, not a vacuum leak) or was the leak after the throttle body (a vacuum leak)? Are you sure you fully repaired it?