[jcp123]

Originally Posted by Miller88

My (former) '01 Taurus, father's 01 F350 5.4 and my '11 Focus idle at asinine speeds to light the cat off ASAP. They all will shoot to 2500RPM on cold start. When the exhaust fell off the pickup, that thing would wake the dead when it started and idled at 2500RPM.

The Focus and the F350 are manual transmissions, and they'll go along 30, 35 MPH with your foot off the gas in 5th gear until the cat lights off. The most annoying thing is, they refuse to idle below 2500RPM when moving. Makes shifting on a cold morning nearly impossible.

My Taurus would go about 15MPH or so shifting into 2nd and sometimes 3rd with no throttle applied.

My Jeep doesn't do that ... I could see it destroying the cat idling for a long time.

2500?! Neither of my Foci did anywhere near that, although my SVT did have an annoying habit of not idling down in neutral, even when fully warmed up, until you came to a dead stop. My Toyota is just as bad, even demanding 1000+rpm when ECT is in the 170s. The Jeep doesn't surprise me, Mopars tend to prefer a lower cold idle...my 5.9 Magnum van and my Dad's old 5.2 Magnum Ram cold idled anywhere from 900-1100rpm.

Originally Posted by Miller88

It's an all-in-one. From Rock Auto, looks like I can get either a 180 or 203 thermostat for $89. I just don't know what is ideal operating temp. I don't want to ruin anything by running it at 203 all the time ...

That's awfully expensive...I'd do a bit more shopping, I spent nowhere near that much. I confirmed a $29.99 price for it at AutoZone. I did opt for factory temperature (180) when replacing it.