Intermittently, my car goes into this mode where it idles high.
When I'm driving it's a little over 1k rpm.
When I put it in park it goes to 3k rpm.
When I shut it off after it does this, it won't start for hours -- as if it's flooded.

The car is a 1995 850 T-5R.

P.S. Intermittent problems are the worst.

 

Do you have a CEL?

 

Sorry I'm still an entry level Volvo guy.
What's a CEL?

Thanks.

 

Sorry a little slow here: CEL = check engine light.
I do not have one.
No OBD II codes either.

Reading another thread I read that it could be the coolant temperature sensor.
Could something like the coolant temp sensor really cause the car to idle that way?

Thank you.

 

Yes but that usually tosses a code. Maybe you have a vacuum leak. Unplug the MAF and see if the idle levels out.

 

It was my Temperature Sensing Unit (TSU).

I searched and read around and found that a faulty TSU causes the ECU think it's colder than it really is.

If your TSU is failing, you can see your in-dash gauge fluxuating.
Normally, when the car warms up fully, the needle stays steady slightly above 1/2 way.

You can tell when it's failing because the needle moves slightly or doesn't go all the way up to the normal position.

When it fails the temperature it sends to the ECU is -40 degrees (default maybe) and the car revs higher to compensate for extreme cold.
It mixes richer and actually does flood and you can even smell gas under the hood.

Several hundreds later, what fixed it was a $30 part.

I miss the money less when I think: "Hey... I won't need to clean or replace my throttle body, idle air control valve, or idle control module (a few more I can't remember) for long time."

 

Where is this TSU?

 

Right next to the thermostat housing

 

So where is the CTS (Coolant Temp Sensor)?

 

Same thing I believe..