I thought I'd post this up with new title
since this is my only problem now.

car: 91 RS 3.1L auto trans.

What I have done: valve adjustment, intake manifold gaskets,
new ECT sensor, new 180 thermostat, adjust ignition timing. and thorough cleaning of every parts on its way.
before this was done, everything was fine.

My symptom: temp never goes over 160, weather in freeway or in town.
in freeway the temp is below 160, I live in CA and it's not THAT cold outside.
in town, temp stays at 160 and once in a bluemoon it would go little past 160
and go back down around 160 again.

my car runs and idles ok, Im not too sure yet but I think Im not running rich,
I didnt notice black smoke nor noticable poor gas mileage.



I just thought I could get a second thought before I change my thermostat
becaz I don wanna change thermostat and coolant and waste my 35bux for nothing thanks all

 

Factory stat temp is 195* on thsoe engines so reading slightly lower on the gague isn't all that surprising.

Just remember that factory gagues are notoriously inaccurate.

It is possible the stat is opening at a lower temp than it's marked for. I've run into stats that were bad out of the box, but only rarely.

You replaced the ECT sensor? Would that be the one that runs the computer or the one that runs the gague in the dash? If it's the one that runs the gague then it's possible the calibration is slightly different than your original one and giving a slightly different reading.

Or possibly the motor is just running better and therefore putting a little less strain on the cooling system.