My 1991 Blazer (4x4 - full size) has been stalling when I am coming up to a stop...but only sometimes, and usually at the same place every time: After I have been driving 25 minutes or so, right before I get to my house! It has a lift and pretty big tires, so when it loses power, it is very hard to brake and steer. It happens in random places too, but mostly in the late afternoons after driving for awhile..it has never happend on my way to work in the mornings. Once I put it in park and stop, it starts right back up. I was told by a mechanic that is could be several things, too many to test, but does anyone have a couple of possible easy suggestions as to what this may be? It has done it twice in the past week, and it is really scary trying to stop & steer. I only lost battery power once, the first time it happened, and it took a few minutes to start again. Now, radio & ac stay on each time it happens. I have read that the throttle body might need cleaning..I don't know if this has ever been done. (I bought it in 2006). Thank you! Stephanie
I just found out the throttle body is clean, the fuel filter is newish and the air cleaner is clean. Was told there might possibly be gunk in the intake manifold. Any thoughts?

 

It could, like the mechanic said, be a number of things. Judging by how old it is, I would put my $ on it's a vaccuum problem. It could also be O2 sensors, sometimes they don't die they just get stuck at a certain voltage and the computer doesn't know the difference so the engine dies. It could be map sensor, or even the egr valve. My suggestion is test the vaccuum of your engine first. A good vaccuum number is around 17 in of Hg. Also hook up the vaccuum gauge with the car at idel and rev the engine a bit. You should see the vaccuum increase kinda fast and drop kinda fast. If it doesn't drop very fast you could have a plugged Cat, or some other obstruction in the exhaust. If that's good see if you can't get a hold of an OBDI scan tool that veiws live data from the computer. These are expensive so if you can barrow one it would be all the better. If not you'll prob need a fluke meter or an analoge DMM to see the voltage change of the O2 sensors wile the engine is running. This will have to be done in park and you'll need someone to push the gass pedal for you to see the voltage change. You will have to be under the vehicle wile it is running so be very careful. You can also check the map sensor with the DMM and the vehicle running.