This is my first post and I have searched all over for resolution to the below symptoms, but could not find anything. Thank you in advance for all of your help on this issue.

Automobile: 2000 GMC Jimmy, 173,000 miles. 4 speed automatic transmission w/overdrive ( rebuilt transmission about 5,000 miles ago.) 4 Door, 4WD, 4.3 Vortec V6 engine.

New: air filter, coolant sensor (replaced 60 days ago), Idle Air Controller (replaced 3 days ago), cleaned the MAF (1 day ago), cleaned the throttle body (1 day ago). Two tanks ago I put BG 44K Fuel System Cleaner in the tank. Last week the Jimmy was in the transmission shop for two days and they could not find anything wrong and did not encounter the below symptoms when driving.

Symptoms: After driving and the engine warms up and I get to speeds around 50 - 60 mph on the highway, the temperature gauge drops suddenly all the way to the left at 100, there is a sound like a miss, (but I'm not sure it's really a miss, it kind of runs rough or hesitates or gets herky-jerky), the tach jumps around and there is an intermittent jerking for about 1 second or two. Then all is well and the temperature gauge goes back to normal. On more than one occasion the temperature gauge dropped and there was no engine hesitation.

SES Codes: none

Possibly related, but not happening since I replaced the IAC (I replaced the IAC due to a code reading), the engine stalled after stopping. Three or 4 times in the past two weeks.

What needs to be done to solve the highway sudden hesitation?

 

change the pigtail on the temp sensor. Had this issue a few times,usually a short in the pigtail.

 

Thanks! I replaced the temp sensor yesterday with an AC Delco one and will try that for a few days to see if there is a recurrence. If the problem persists, then I will try a new pig tail.

 

Yep, I had a loose connection once, did the same thing

 

It has been 160 miles since I replaced the replaced Coolant Temperature Sensor and I have not had a temperature drop or sudden hesitation. I hope it is fixed. Thanks for everyone's help.