I have a 1993 Regal 3.8L and the engine doesn't like to heat up and I've been having this issue for years. I did the whole feel the coolant hose thing and it would appear the thermostat is stuck open. I replaced it a couple years ago and I don't recall if fixing the problem. Do these engines not heat up well? Do I stink at replacing thermostats? Wrong type of thermostat? Any suggestions or common experiences? Thanks

Random but possibly useful information:
Highly doubt it matters but I unplugged the low coolant sensor. The radiator cap was replaced a few years ago with a cheap autozone one. The coolant is not the special gm stuff. There is some oil in the reservoir but the overall coolant quality is acceptable. I once drove the car with a burst upper coolant hose back from snowboarding a long time ago.

What signs do you have that the car is not warming up properly?

I am at operating temperature with the thermostat opening when I get on the highway on my commute, which is about the 3 mile mark, or 5 minutes. I am usually rolling within 30 seconds of starting, once the idle starts to settle down.

What part of the country are you in?

The car warms up to only around 130 to 140 after a few miles of driving and stays there if I'm moving. If I'm in stop and go traffic it will creep up to around 180ish but once I get going it drops back down within a minute or two. The car has some hesitation for the first minute when cold while accelerating but seems to run fine with so-so gas mileage (10 to 15 on street).

This thermostat issue is not really a make or break thing since the car gets me where I need to go. I was mainly trying to gauge what other people'* operating temperature is. I would think it would be more in the 180 to 200 range.

I live in Los Angeles so cold weather is not a huge issue. I lived in Michigan for a year and the heater worked less than ideal and took ages to warm up.

How are you getting the coolant temperature? From a scanning tool or the gauge?

What temperature rating is the T-stat you installed? Sounds like you might have put in a 180, and you need a 195. Regardless, put a new T-stat in (195) and get rid of that cheap rad cap.

I'm reading from the dashboard gauge so all readings are approximate. Don't own an OBD1 scanner.

I believe I bought the 180 thermostat last time so I might give the 195 a try.

I do want to throw this information out there for you, GM gauges can be pretty wonky.

In my Regal, I believe I have a stock 195* unit in there. My gauge rides halfway between 100* and 220*, we'll call it the quarter mark. With the Scanner, I have confirmed that coolant is about 185-190 in this area, which would be fairly consistent with what I have seen in other vehicles running a 195* unit also. When I am stuck in stop and go traffic, then the gauge starts to climb, until reaching about the 220* mark (halfway), where the fans start to cycle to pull air through the radiator. My guess is that the first 1/8-1/4 of the gauge is the 'cold zone' for lack of a better term, spanning 100*-160*, and then the remaining 3/4 of the gauge spans the remaining 160-260*.

My mom has a '95 Blazer, which I also thought was running too cold, because it would very rarely get to 1/4 on the gauge, and has similar markings as the Regal (100*, 210* middle, 260* hot). I plugged in the scanner, and found that the truck was actually running 170* , consistent with regulation by a 180* thermostat. Again, GM gauges at their finest, LOL.

The only possible gain in running a 180* thermostat in the naturally aspirated application is having the transmission cooled by 180* coolant, as compared to 195* coolant. If you are indicating marginal coolant condition as well, a coolant flush could be good, as well as a thermostat replacement. The only real trick to these is to make sure there is a rubber ring gasket around the thermostat before installing, and to shove that whole thing in the recess or shoulder of the thermostat housing, and then reinstall the housing with the thermostat stuck in it. A small hole or pre-drilled thermostat helps with refilling because it allows air to pass through it.

If there are other hoses or parts of the cooling system in need of replacement (like the coolant bypass inlet that I believe was plastic in 93, and WILL break eventually), you may as well do it now.

Best way to check is steal your wife'* meat thermometer, and stick it in one of the air registers....command full hot.....on a hot engine you should easily get 140-165F on that thermometer.....

In some karma for taking too long to respond to your advice my car decided to stop running and needed to be towed home. The thermostat was not an issue and after looking at the gauge with a new baseline, like you suggested rjolly, it seems to be running fine.

Not sure if I should post a new thread but here'* my current problem...

I was driving and it stalled while braking. After like 15 or so minutes it started up again and died a few miles later and I towed it. Hasn't started up again. Cranks but not start.

So here'* the diagnosis so far. It is throwing a code 17 camshaft sensor error. There is no spark (checked 2 wires on different coils using inline spark tester). I can hear the fuel pump turn on. Have not checked fuel pressure or signal to injectors. No visibly blown fuses (it is dark but the ecm is not blown for sure).

Any suggestions on where to start? The impression I've got in the past is that the cam sensor controls the injectors but not the spark plugs? It seems more like a ICM, ECM, or crank sensor problem. I did have some timing issues in the past but it was fixed by replacing an arcing spark plug wire. Last I checked, the coils (original) had about 5.6 ohms (a bit low) and might of slowly killed the ICM (original). The ECM is not original and I have the original that was working when I pulled it (chip is original).

I would clear codes by disconnecting the battery for a few minutes, and then trying to start it again.

If Code 17 comes back, then that is probably your answer.

Here is some nitty gritty on code 17 that I found on the interwebb:

And basic theory:

3800 GM Ignition System Description and Operation
From what I gather, this is a very specific code, essentially the PCM is seeing one signal from the Crank position sensor, but not the other. So, wiring, ICM, or Crank position sensor are to blame.

I don't believe this is Cam sensor related, because that is code 41, and the PCM only uses that to reference when cylinder 1 is passing, which I think is only important to, as you said, injector timing. A failure would not drop the car dead while running, and would only mean that injector timing has a 1 in 6 chance of being correct, which does come with it'* own symptoms.