I have a 94 Blazer that works perfect when it is cold, however after it heats up and still runs fine, shut it down, restart it and all hell breaks loose. At different times and totally unperdictable it will go to a very high idle, Very Low Idle, and stalls. I have had it in the shop for 18 out of the last 21 days and no avail. I have it back now and not sure what to do next.

So far I have replaced the following.

Ignition Control Module (under the distributor)
MAP sensor
Idle Air Flow Valve
Throttle Position Sensor
All vaccum lines
Plugs
Distributor cap and button
Catalytic Converter (other reasons a while back) It was removed and verified open however). Exhaust has good flow.
Fuel Pump and Filter

Computer is not sending any codes (obd I) and the SES light never lights when it is doing this. SES light does work however.

Engine is a Vortec 4.3 Vin W engine with A/T, & Air. Blazer has Tahoe package if that makes any difference. Approx 150,000 miles and believed to be the original motor.

I hate to say this, but i am getting very fustrated with this one, and not sure what to do next.

Thanks in advance for any assistance on this.

Sparkie

 

Have you guys checked the Distributor?
I found that my blazer would not start when it was moist and damp out side. Then one day my wife drove the blazer and it cut off. It totally stalled out when she drove a half a mile from the house. We had the blazer towed back to the house. I tried starting it again in front of the house. It would try to start but not turn over. I was suspecting the distributor all along. My blazer has been acting weird ever since I replaced the cap and rotor from Auto Zone. I found that using bosh cap and rotor plus wire and plugs does not make your truck run as smooth. OK, what I found was my distributor cap was getting moisture in it. I saw that the pins in the cap had condensation on them. I went to the dealer to get the original cap and rotor made by AC Delco. I replaced the cap and rotor but this time I put a little bit gasket sealant around the cap just to make it air tight. I connected all my wires and then turned the key to see if my truck would start and it did. It has been running for weeks with no cut offs. It has rain and was very moist and wet out side. So far no issue it still starts fine. However I get the sense that my distributor may be on the way out. Because the tuck is not putting out power when I for it. It seems to be very sluggish, rough idling and poor fuel economy. My engine misses under load while accelerating. The next step is to replace module on the distributor. I believe the distributor module may be going bad.
I’ll let you all know what happens.

 

I have a 94 full size blazer that I had similar problems with after I installed a throttle body riser (vortex). It turns out that I had my throttle cable in a bind.

 

Still having the same problem. I have replaced the following so far:

All Vaccume Lines Plugs Distributor Cap & Button) (X2) Cataltic Converter (Other Reasons, Removed and veified to be open) Fuel Pump & Filter Ignition Control Module (X3) Map Sensor Idle Air Control Valve Throttle Position Sensor Computer Module Coolant Temp Sensor
Still doing the same thing. 1st run being cold and runs perfect, 2nd run after it is up to temp the idle will go way high, then way low, stalls. Not necessarily in that order. The other day while test driving, had front breaks locked up on grass and went to such a high idle that it would not stop. Had to get into Neutral. Almost ran me into a tree (sorta wished it had and totaled it), anther trip driving down the road the idle went so high that I was ridding the brakes to stay at 45mph. When slowing down sometimes it goes to such a low idle that I have jokey the throttle just to keep it from stalling.

I have inspected the throttle body and is smooth and no binding, checked the throttle cable and no defects noted. Have checked the wiring and all seems to be in order there as well.

Any advice would be appreaciated.

 

Did you ever figure out what the problem was?

 

i am betting coolant temp sensor. symptom in first post said it runs bad when warm.