Recently my 2000 GC Laredo has been stalling at stop lights, etc. When I start it up in the morning the temp gauge does not register any change as the engine warms up. After a few minutes of driving the engine starts to feel sluggish and tries to stall out when accelerating up hills, etc. When I pull up to a stop sign or light it will stall out completely. However, sometimes if I stop and shut the engine off for a short time and then start it up again the temp gauge registers and everything seems to run just fine!

Is this possibly a problem with the temp sensor, the thermostat, or something else? The coolant levels are constant so it doesn't seem to be losing it anywhere. I did an oil change the other day and there was no water/coolant in the oil.

 

It will run rich if the computer thinks it's still below operating temp. Kind of like driving with the choke on on carburated old geezers. See the link. its over simplified but explains how the sensors all interact.

http://www.fuelpumpu.com/news-engine...fuel-flow.aspx

 

Sludgy coolant may cause an erratic reading from the temp sensor. If your coolant is clean I'd vote for putting a new temp sensor in. Inexpensive and easy to change. My dad had an old Ch.vy truck and the temp sensor failed and we chased ignition and fuel problems all day because it ran like it had only partial spark and tons of black exhaust, unplugged the temp sensor and the thing cleared up almost instantly and ran great... Put in new temp sensor for $12 fixed it completely.

Just my 2 cents....

 

Have you ever seen a "check engine light"?

If so, even if the light isn't currently on, you should retrieve the code from the computer for clues/guidance on root cause.

 

^ what he said