Bouncing Temp needle, and bad idle????

[Skibug]

Could a bad thermostat be the cause of my bouncy idle? I noticed for the first time last night that when I came to a stop and put it in park, the temp gauge needle started to bounce eratically when the bad idle would begin. I have done replaced and cleaned everyhting else that seems to cause these engins to not idle properly. I was just wondering if the thermostat can cause this also? And is a bouncing temp gauge needle usually a good sign that the thermostat is acting up or is something else to blame?

I am going to be spending all of today to change my oil, drop tranny pan and change that bit of fluid and filter. And I thought that if the thermostat needed to be changed, well why not do it today when everything else is getting done on the truck.

 

[Rhett]

Sometimes, when a car starts overheating (like from a stuck closed t-stat) the computer will detect this and increase the idle speed, so that the clutch fan spins faster. Then once it cools a bit, the idle (and fan) slows back down.

I would change the stat for sure while you're doing the other stuff, since you're getting dirty anyway, might as well. I suggest buying a couple of stats, and boil them in water to test them--make sure they open at 195 degF or so. Return the bad ones.

 

[Skibug]

Done!!!

Well after a few hours of work, the trans oil was changed, engin oil changed and thermostat was replaced. Still no help on the bouncy/rough idle though. For those that complained about changing the thermostat, I found it not that hard to change. With a 12" extention and a Universal, that 3rd bolt was a piece of cake. My trans fluid was pretty dirty and I will do another change in a few weeks to get more of the old stuff out. But man was that job messy. I got trans fluid all over the place. You need about a 12 foot catch pan to get all that stuff that splatters all over the place. And then it seemed like everytime I got the pan under everything, it would run down the crossmember outside the reach of my catch pan.

Just thought I would give an update after everything was done and let you know that the thermostat did not fix anything with my idle problem. Although my temp gauge needle does not bounce around now.