Cooling system problem-94 Ciera S 3.1L

Hello! Well, I had a problem with the engine running too hot for a while here...about 6 months or so. It wouldn't overheat, but it just gradually kept getting hotter, until last week there was a pretty bad leak, but we couldn't find any cracks. It turns out the pressure was VERY high in the coolant system, and the radiator was in real sad shape (we eventually found some nasty blockagei n there too), so we replaced the radiator and the cap for it. We had recently replaced a worn belt, so that was in good order as well.

Well, we got everything back up and running, ran the engine and got (or so we think) the air out of the system. After driving it around the block (more like 2 or 3 blocks, I'd say), I was upset that it was getting around 3rd white marker (beyond 220 F, but not up to the red lines) because there was heat coming through when we cranked the heater up. We replaced the water pump with a brand new one last year, so that part is definitely running good. We noticed absolutely no leaking whatsoever, too, though we did notice that the fan NEVER turns on anymore. Furthermore, when you crank it over, it feels like it is misfiring very, very badly--you can practically see the car shaking from it. This feeling goes away immediately when the engine is warm, and won't happen if you start it up after recently driving it.

This only seems to happen when it is cold, and it is a recent development (a week old). I did a lot of maintenance when it reached 130,000 miles, replacing a lot of sad-looking sensors, so a lot of them are in good working order. In fact, you'd have to listen to see if the engine is running when at idle, because it is absolutely still when idling. I noticed that the engine stalled once when that sensation started (I installed new plugs and wires last summer, too), and the car seems to take longer to crank over ever since this cooling issue started. Someone mentioned a certain sensor, but he couldn't remember what the name of it was. Does this ring a bell to anyone?


EDIT-It appears that someone in my family has taken it to a local shop (Pro-Tech Automotive is the name, they have a big facility) to have them fix that last issue because "this week is going to be too busy." While I don't argue this fact, I kind of wished I had the chance to fix it myself :-/. Anyone care to speculate on what they think the problem is anyways? :)

Well for the fan not turning on, it could just be bad. Or like on my 94 Olds Cutlass Supreme 3.1 V6 I had to replace the Coolant Temperature Switch/sender, before I just replaced the Coolant Temperature Sensor, which was in bad shape but only worked the guage inside the car. So your Coolant Temperature Switch/Sender could be bad. (Also check wiring, and relays in fuse box under the hood.)

As for the missfiring, maybe there is a clog somehwere in the manifold, *Shrugs*.

Here is a link to advanceauto parts for the Coolant Temperature Switch/Sender (Note: This is with guage, not light. But I think you have a temp guage on your dash) http://www.partsamerica.com/ProductDetail.aspx?MfrCode=NIE&MfrPartNumber=TS25341&PartType=425&PTSet=A (http://www.partsamerica.com/ProductDetail.aspx?MfrCode=NIE&MfrPartNumber=TS25341&PartType=290&PTSet=A)

Good luck.