I just bought this car sunday and on the test drive it blew low heat. I was told it took awhile for some reason. Sure enough after about a half hour of driving it got to warm. So I turned it off and rolled down the windows. now it got to cold and turning the heater back on gave the same slow results. I read a few threads to figure out why my 1997 Z28 heater takes forever to heat up. The temp works its way to the hash mark between 100 and 210. Really never goes over that while driving. The radiator fan seems to turn on quick. the one to your left if standing at nose looking in engine bay. I changed the Thermostat, felt the out and return lines to radiator, both were warm. Standing at the nose of the car the right heater core line was hot enough were i could not hold it long, The one on the left was warm and i could hold it all day. ok there is a burp valve on the thermostat neck and another on heater line a few inchs from the other one on housing , I bled them both. still same results. slow heat. I think because of the med heat on the one heater core line that it is semi plugged. Your thoughts ??????

Now for the not starting. I rinsed the motor as when I burped the heater core line, radiator fluid went shooting out the little hole everywhere. When I burped the hole at the thermostat housing the bleed hole was pointing towards the block. It squirted water out till it was a good flow and I shut the valve. It is at that time the motor stumbled and shut off. I checked the temp and without the fan running temp climbed just below 210, so almost mid way on Gage. Thats when I remembered the optispark. I looked and the burp bleeder water vented towards two electrical plugs. One that has a red top just left and a little down from the radiators water neck and the other about 6 inch below that. do either one of those make the car not run. as now it just turns over and does not fire up. I put a code reader on it with no codes thrown..... Any ideas on either issue ?????

 

It dried and fired right up, had a service engine light on now. I busted out my code reader and it said IC4 To few pulses. I cleared it and waiting to see if it dried up or is going to throw the code again. Now back to that heat issue ???

 

Congrats on the buy.
Welcome to the Club
Reads like a slow actuator for the Temp door or a twisted heater box.

 

sounds like you got the opti wet, or maybe the coil wire got wet, plug wires may be getting on and throw sparks when wet, not letting spark get to plugs. heater core could need flushing, restrictor in heater hose may be pugged.