Coolant Temp. Override

[dgreer]

Hello and thanks for your great web site. I am a recent purchaser of a 1990 Grand Wagoneer 62000 original miles, needs paint but generally a solid truck and i love it. I intend to use it every day to and from work and pick up my kids from school so I am trying to get all the little bugs worked out. It idled and ran a little rough when I first got it but I knew it had been sitting for a few months so I ran some good gas and Techron thru it and that helped some bot not enough. My very gracious and ,smarter than me neighbor, put a kit in the stock motorcraft 2bbl and he fine tuned the idle mixture and it purred at idle and up through about 1/3 to 1/2 throttle. After that even though the engine was not missing and sounded strong we weren't going anywhere, almost the way a clogged converter feels but i still felt like it was the carburation, smelled rich a lot.
So I ordered the JEEP factory service manuals $112 ouch and started reading. By way of the manual and some discussions on this web site I began to narrow things down, no vacuum leaks etc.
To make a far to long story shorter I disconnected both of the CTO swithches or valves on top of the intake manifold and plugged all three hoses of each. It runs great thru the full range of throttle shifts perfectly. I am ecstatic.
Not one to look a gift horse in the mouth usually, I would like to be sure I am not damaging anything and I wonder why this seems to have solved the problem.

[coolram]

You probaly have a CTO either not opening or stuck open which effects your vacuum advance and your EGR.You can run the way you have it with no problem unless where you live has smog checks.

[Bob Barry]

Well, the CTO's are more for cold-weather driveability than for emissions, so I'd replace them. The problem was probably a leaking CTO (they can get loose in the housings and cause bad vacuum leaks). You can check out the chart in my sig below for the aftermarket equivalents to the factory part #'s (your truck should use the top three CTO's in the chart).

Good call on that manual, though; you'll save that much over the labor on the first job alone.