We are out of Ideas... weird problem
 

So about a month ago my 95 chevy blazer (4-door/ with 4 wheel drive) started to idle high. it was colder so i didnt think much of it. Well after awhile it got 'worse' and would go about 20mph without pressing on the gas and not going down hill. It was to the point it would over power the rear breaks which were new 4 months prior. lines in good shape too.

When we hit the sub zero -10 and -20 below it started to get worse, dangerously worse. It was so bad that I went to drive home from work and went to stop at a stop light and the whole back end (not pressing on the gas) spun out of control and whipped me into on coming traffic. luckily we have some observant winter drivers around and seen what was happening. I threw it into neutral and the engine revved out of control pushing the oil pressure gauge up over the maxed out point. I threw it into 4 wheel drive which helped considerably on the way home. In two wheel i could go 50 and not push on the gas. before every stop sign/light i was forced to put in neutral just to STOP. luckily small town = only 5 lights. I parked it.

after the cold snap it seemed to get 'better' and go back to its previous condition. however it seemed that I had from the pressure blown the cat and/or a whole in the exhaust system. So we went on some suggestions from friend to check the throttle linkage, WD-40 up the wazoo. no change. Checked two of the main sensors, they were functioning properly according to the chilton manual. while checking things out noticed someone had pulled out my vacuum hose. we re-attached it but, no change. we then began to look for a leak and didn't find any. We are at a loss. All the local garages cant get me in for almost a month, i can change the part if i know which one to change as Ive grown up in a family of chevy parts changers :D

I'm out of guesses. Not sure if its related but the sensor/part that controls the engine "break" when you are coasting for more than a minute over 50/55 quit about the same time that this all started to happen.

also that might be related our 4 wheel drive 'clunks' out but, never in. had the differential checked but the garage said both front and rear are full of fluid the seals are in good condition and working ok. they suggested it could just be the actuator?

ANY ideas are considered helpful, id like to get my baby back on the road.

First thing I would do is check the IAC. Pull it out, clean the pintle and the throttle body. If its hanging up, its gonna alow more air into the intake manifold, thus making it rev. If that doesnt work, it might need replacement. Are you sure you don't have any vacuum leaks? A cracked intake gasket, or a cracked upper intake plenum could be the cause.

Alright we will check that asap (tomorrow). We will check those gaskets too.

Alright, let me know how it goes!! To check for vacuum leaks, what I do is take a big ol fat cigar, start the engine up then take a big whiff. While its running, blow it over the engine, if you see it getting sucked in anywhere, you have a vacuum leak. Then when your done you can sit and enjoy the cigar! Its a win win!! Lol

HA! thats clever!

Check TPS sensor and connector. I had a bad connection between the connector and the sensor. Wiggling the connector would change the idle speed. A second option in case nothing turns up with the IAC.

Thanks. like I said some ideas are better than no idea...

very very clever farley, man you are full of good stuff today!!!