What were the 3 temps for the times you have?

 

I think I was engine off at about quarter to 8am today. All readings are in Fahrenheit

Noon
Ambient: 29
Coolant: 73.4
Intake: 57.2

2PM
Ambient: 29
Coolant: 53.6
Intake: 46.4

4:30PM
Ambient: 29
Coolant: 42.8
Intake: 37.4

 

alright I got my temps this morning.
ambient 19
coolant 24.8
intake 19.4

tstat off? I did a rad swap over the summer but I think its an auto bleeder, one of those standt lev -r caps

 

The thermostat has no affect on the three temps after a 12 hour soak. That's the reason for waiting 12 hours, to let the coolant, block, and all of the sensors acquire ambient temperature Your screenshot shows what temperature the cooling system is regulating at, which is too low, and that's why the thermostat needs to be replaced.

By comparing the three different temps, the chances are that two will be nearly the same, which they are, ambient and IAT are almost exactly the same. From those results, the "odd man out" is the ECT sensor reporting almost 6 degrees too high. Start with replacing the ECT sensor, and then check all three temps again to confirm the repair. Yup, gotta wait 12 hours again to equalize temps. If the three temps agree with each other, then it's time to move on to the fuel delivery and see what fuel pressure and leakdown are. Let me know when you're ready and I'll walk you through it.

 

I don't think I was at 100% operating temperature when I ran the data, so the thermostat should be fine. I meant to rerun the test today right after work, but I totally forgot. Last time I only turned it on and went for a small drive around the block. Maybe it wouldn't hurt to replace it anyway depending on how old it is.

And, while Im at it, do I need to get the ECT with the wire or will just the sensor itself do?

 

There are two coolant sensors on your 97: The sensor for the dash gauge is in the left cylinder head and has one dark green wire. The one for the PCM, (the one you need to replace) is in the intake manifold and has 2 wires, yellow and black. If the connector does not fit tightly or is damaged, it needs to be replaced. Most auto parts stores can get the connector, it comes with the wires, (pigtail) attached. The wires must be soldered to the vehicle harness, no crimp connectors allowed

After you replace the sensor, take it for a ride and bring the engine up to operating temp. Connect your scan tool and see what engine coolant temp shows while the engine is running.

 

engine temp this morning after my drive in was 183.2... is there a difference between the pcm sensor and the gauge sensor? I had a look on rock auto and there aren't any I've seen that denote a pcm sensor. they do have ones that say "w / gauge " I presume isn't the one I want

 

This is the sensor for the PCM: Buy Delphi Engine Coolant Temperature Sensor TS10075 at Advance Auto Parts#

When you look at engine coolant temp on your scan tool, this is the sensor you are seeing. The sensor for the dash gauge is different, it only has one wire.

1998 and newer only have one sensor, the one in the intake manifold. The data is sent to the BCM and shared with the PCM and the instrument cluster. 1997 and older do not have a BCM, that's why they need two sensors.

Think about this... your ECT is reporting 6 degrees higher than it should, we already know that from your test results above. This means your actual operating temp is more like 177F ...trust me, it needs a thermostat, AND the ECT sensor. You're freezing your hind end off needlessly

 

Thanks Cap, that's the exact same looking sensor I saw on Rock Auto but looks are apparently deceiving. We're getting something of a light snow out in Cincy... Putting a heck of a delay on me here.

 

Why not get it at Advance? There's one in West Chester. Probably have the thermostat too.