91 will sometimes stall out in park

91 with 1.9 liter. Did the timing belt a couple of months ago. The car has plenty of pickup and runs fine and will stay running at idle in gear but if I have driven it for a while and park and leave it running it will start to surge and almost stall out after a minute, then the idle will surge up faster again and then almost quit and does this a few times till it dies.
When I get back in and restart it, the thermostat is up 3/4 of the way which is a bit hotter than it usually runs. This olny happens after driving and then parking and leaving it to idle.
I checked and cleaned the pcv and looked for vac leaks but didn't find any. I did hit the throttle under the hood and it has a hesitation/bog and a hiss before the engine revs

Vacuum leak... find it.

Thanks, I'll go over all the vacuum connections around the throttle area again.

It will surge and die only when idling hot. The idle is ok when cold. I would have thought a vac leak would be just as bad not matter the temp unless maybe the intake gasket? Plus it idles ok when I am stopped at a light. It only starts to act up after driving. When it starts to act up the temp gauge seems to go way over it's normal range up around 3/4's on the idiot guage.

I just had aproblem was just like that on a 93 Escort. Except my car was not over heating.

Clean the Mas Air FLow Sensor. But becareful not to break it. The two little probes on the sensor should both be shiney and clean. If they get dirty the fuel injectors freak out, and can cause some of the worst surging that i've ever seen!

It's possible that your car is over heating because the engine is leaning out, due to the dirty MAF sensor.

The good news is, it's really easy to check. It'll only take you 10 minutes to check it out. It's usually bolted right to the airfilter box.

Could possibly be due to a bad PCV or plugged up EGR causing gases to get backed up?

I only skimmed over your original post before and saw the word "hiss" which made me assume vacuum. It shouldn't be too hard to figure out once you start messing with it.

I think the hiss I heard was just the air going thru the Idle control valve, I sprayed that out with cleaner. I had cleaned the pcv valve when this started and it didn't help.
I'll check the maf and check on the egr next
Thanks

91 with 1.9 liter. Did the timing belt a couple of months ago. The car has plenty of pickup and runs fine and will stay running at idle in gear but if I have driven it for a while and park and leave it running it will start to surge and almost stall out after a minute, then the idle will surge up faster again and then almost quit and does this a few times till it dies.
When I get back in and restart it, the thermostat is up 3/4 of the way which is a bit hotter than it usually runs. This olny happens after driving and then parking and leaving it to idle.
I checked and cleaned the pcv and looked for vac leaks but didn't find any. I did hit the throttle under the hood and it has a hesitation/bog and a hiss before the engine revs

Vacuum leak. They run ok when cold because the engine is computer set to run rich until warm and can handle some extra air. After they warm up, the engine is set to idle ultra-lean and any extra air is too lean and stalls.

For a few seconds after a part open throttle run mode, the engine gets slightly more fuel and may idle yet. But within 10 to 30 seconds, the engine goes to full ultra-lean extended idle for emissions. Then even a small air leak will kill the motor.

Any engine will indicate a high temp gage if the key is turned back on shortly after warm run. The reason is that hot cylinders heat-soak the sensor for a bit because no coolant is flowing with the water pump off. No cause for worry, but it is the same reason that extra expanded coolant may even bubble into the reservoir after shut-off. Excess trapped heat. The coolant returns (sucks back in) as the motor cools down all the way ...if the system works properly. This is the reason the reservoir should never be filled completely ...so that there is room for this expansion.