Hi I have a 1995 s-10 blazer 4.3l vortec v6 with EDI ignition, the truck was running ok, but had the surging idle problem every time when i would first start the truck or when i would decelerate, and sometimes stall when coming to a complete stop. i believe the problem is being caused by the TPS, i just haven't replaced it yet to see if that takes care of that particular problem. now the probem im having the most trouble trying to figure out is this...when i would try to start the engine sometimes it would fire right up, and then other times i could run the battery dead attemping to get it to start. recently i have replaced the distributer cap, rotor button, all plug wires, new plugs, new ignition coil, new battery, and newer alternator. the fuel pump does run for 2 sec when the key is turned forward...is it possible that my ignition module is bad? or maybe crank sensor? i don't believe it to be a fuel problem, seeing how once it is started, it runs fine. the battery was just replaced this past friday, and i recharged the K&N air filter as well after i replaced the battery. the truck ran fine that day, but now in the past two days i haven't been able to get it to start.

 

I would recommend checking and cleaning the Idle air control valve (IAC) which should be located right next to your TPS sensor in the intake.

A sticking IAC would certainly cover all of your trucks symptoms for the idle and stalling problems. If the valve is sticking fully closed when you try to start the truck then it will be starved for air and will be difficult if not impossible to start.

These trucks are notorious for getting the IAC clogged up with carbon deposits. Not just those dry sooty easy to clean ones either. The IAC tends to collect the sticky gooey type deposits that tend to harden up like glue when the engine cools.
Sometimes just a good cleaning of the IAC and the throttle body seat will do the trick. Though often you will end up replacing the unit.

If nothing else get yourself a OHM meter and TEST your TPS sensor before shelling out the cash to replace it. There are VERY few electrical components on this engine that you cannot easily test with a volt/OHM meter before spending big bucks to replace a potentially good part.

I see way to many people dumping a lot of cash on new parts that aren't needed when the old ones can be tested first with a $10 tool from radioshack.

 

here's a interesting thing...I hooked up a charger to the battery and set it on 12 volt start...this caused the engine to crank abnormally faster than it would have just with the new battery, and the engine started. ??? wonder why, because i can't have this kind of cranking power with only the battery! and another question...i couldn't locate the IAC in my haynes manual...i have the multiport injection on this engine. is it the larger electronic valve below the throttle body opening?

sorry i answered my own question...it's the EGR, still haven't located the IAC yet though.

 

This should give you a rough idea of where it is:

 

found the answer to my question again...i located the IAC and according to the haynes manual you sould read a resistance value between 40-80 ohms across terminals A&B and then also C&D...i metered them and got 52.5 across both sets of terminals. so according to the manual it is still in working condition. i did remove the IAC and cleaned it...but should the plunger on the valve move in and out? because mine does not. even after cleaning it.

 

You can break the IAC valve by attempting to move it manually.

 

ok thanks... well as far as i know it's still in the same condition as it was when i removed it. i reinstalled it after cleaning it, and metered it afterwards as well. it just looked as if it should move in and out, because of the spring on it. i just attempted to move it, and it didn't have any in and out movement to it. but i didn't try to use any excessive force.

 

While you really shouldn't be moving the motor manually it is necessary for it to be able to move. It also shouldn't take much force to move it at all.

Yes there is a small possibility of damage if you try and force things to hard and to fast but if it is already stuck then it really doesn't matter now does it? The pintle should move rather easily if everything is working as it should be. The chances of damaging a good IAC by moving it a small amount slowly is almost zero.

If you don't want to move it manually you can also check it's operation by simply turning the key and listening. When you turn the key to on the valve should cycle. Quite often you can hear it do so but you can also feel the motor vibrate slightly when it does.