Need Lotsa Help

Ok guys, so here is the deal, the truck for some time now has been running right at the 235 degree mark. I notticed that my clutch fan would spin faster due to it engaging, but not like it had in the past to get the temp back down to the 210 mark. So i replaced the clutch on the fan, still no luck, engine now seemed to operate at the 235 mark, would not go above that, and even with the air off would not go below. this happened on sunday. I drive to work yesterday not problem. when i go to leave work i start the truck to get it cooling, then go in the office to finish the last few minutes of the day. I come out, leave and right as soon as i get on the highway it dies, but not fully, it seems to run right around 4-500 rpm, but now power would not accelerate. i pull off to a safe portion off the road, and attempt to start the truck, it seems to try but kind of lugging. I hear air coming back through the intake, and a very bad odor. Now my first thought is plugged Cat, but I am not sure that it would happen just all of a sudden, I have read through some of the posts and I am at a complete loss, however I need to get this fixed. Much Help please.
 
Joel

Well Im not going to lie. I dont know what to say, but you could check your temp. gauge, and temp. sending unit/sensor they could be bad and it is really at 260+
 
Second I would do is the thermostat. I put in a 190 instead of 210, and it stays nice and cool. It should the whole cooling system is new,
 
Next post tell us what kind of vehicle,/miles,/engine,/ect.
Hope any this helped good luck. 

My bad its a 2002 Blazer ZR2, It has a 185 deg thermostat in it.

I have heard some good and some bad things about putting in a lower temp thermostat. If you go too low the engine will keep adding more fuel trying to make the engine heat up......dunno if yours is too low or not just know that, that is one of the possible outcomes.
 
Have you checked your radiator fluid as to the overheating (stupid question I know but some people don't look)? If you checked the fluid is it discolored at all? If its gunky and dark it could need to be flushed and filled. Also it could have a blown head gasket putting oil into the fluid. Head gasket would also account for some of the loss of power.
 
When you smelled the bad smell, what did it smell like?
 
Have you tried unhooking the exhaust from the cat-back and seeing if it would start then?

On the newer OBD2 vehicles, this can cause excessive fuel usage as the PCM will not go into closed loop until the engine reaches something like 175*F or 180*F.  With a 180*F stat, you will set a code and it won't run right.  Best bet is to stay with the 195*F stat that the general put in.

Dang I thought the 190 thermostat could have been helping.
 
The guy befor me said he got 18+ mpg with it, and I get 14- as soon as I get it running to temp.
 
Never mind scratch the lower thermostat.

Mine runs between 200-210 on a 90 plus degree day and with the a/c 220-230 ish the dealership said that it is a common thing with all GM trucks to run hot like that (they don' t consider it hot) and he said it for emissions reasons due to fuel mixture and if you put in a lower thermostat it (as long as it is above 190 it probably would hurt anything but he didn't recommend it as he said they did it on a shop truck to test and they tested emissions at the dealership and he said it didn't pass. They tried with 185 degree thermostat. So mine still has the 195 in it and it never goes past 230 ish. I guess the guys at the dealer are probably right.