92 fox temp gauge funniness

[Boosted92LX]

Ok, I haven't owned this car for very long. I drove it home 1200 miles from where I bought it without a hitch. Now, the temp guage is doing funny stuff.
Driving it home I assumed someone had put a 160 degree thermostat in it because the temp never got far above the "L" in normal.

View attachment 187299

I've notice lately that the temp has been running lower, and the needle fluctuates.

Yesterday I drove it about ten miles to work and I got a check engine light. Looked at the temp guage and it was bottomed out, below the 130 line. So, I romped on it pretty good for a ways and bingo, guages rises up to where it normally stays, and after a bit, check engine light goes off.

Before driving home that evening, I checked coolant level, it's fine.

Drove home, guage never rose, check engine light came on. beat hell out of it again, check engine light goes off, temp guage never rises.

This morning, I took it out around the block, temp guage started rising, fell back down to nothing, then rose back up to a little higher than the picture, and then settled down to where I then snapped the picture.

Could the thermostat be sticking open? I didn't think a temp sender failure would behave this way, and I'm getting a check engine light which goes away..haven't check for codes.... Anybody have any clue?

 

[TenorPlayinGuy]

I'd say it was the coolant temp sensor. Since if the thermostat was sticking it normally doesn't move.

 

[ID89GT]

Could be a faulty sending unit for the gauge as well. But that wouldn't cause a check engine light

 

[HISSIN50]

You answered your own question. Start with pulling codes to see what's going on. You might also want to use another means of measuring temperature, as the stock gauge is not accurate enough for doing diagnostics.

Good luck.

 

[2000xp8]

Start by changing the thermostat, a mr gaskets 180 is only like $10.
I've used a 160 and it's barely enough to read on the gauge and if i remember correctly on cooler days it did throw the light.
If the gauge still reads inconsistant just buy an autometer full sweep mechanical, don't waste too much time screwing with the stock gauge.

 

[Mustang5L5]

Next time the check engine light comes on..pull the code.

These cars don't trip a CEL for engine temp..there is another cause.

Edit: unless it's code 21....coolant temp related

 

[HISSIN50]

The code should be stored even if the CEL is not illuminated in real time.

 

[Boosted92LX]

OK, thanks fellas! I'll try to pull codes in the morning and we'll go from there. I'm really thinking it does have a 160 'stat in it. I'll check it and see. A buddy of mine told me he's seen them stick intermitantly, and it doesn't take much to change it.
As always, I appreciate the feedback!

 

[MadRed92GT]

I'm having a similar issue, mine is the temp gauge is going up to the o in normal. I've changed the t-stat with new gasket & new radiator cap still going up to the o in normal. Any suggestions?