Service Engine Soon Light and Rough Idle (Below 1200 rpms)

Check engine light on? Have it scanned and if it is a p0420 code, that will a catalytic converter code. That will make it run rough and not run well. Usually the catalytic converter will be stopped up. If no engine light on, unclear of what it could be but I hope you get the issue resolved. Thanks and Jesus loves you John 3:16-17 (KJV)

-There is couple things cause that. Possibly:
-Spark plug too dirty, pack w/carbon, oil.
-Broken plug wire.
-Bad injector.
-dirty air flow sensor.

Good luck

Mai

Sounds like a dirty air filter is putting the mass airflow sensor out of range. The throttle position sensor is subject to physical wear, the age of your truck warrants replacing it. The coolant temp sensor controls the Idle Air Solenoid which determines idle speed ( cold, high idle, 1200 rpms open loop mode for the ECU) and (hot, low idle, 800 rpms, closed loop mode for the ECU) If the truck does not have a Mass airflow sensor, check the Manifold absolute pressure sensor (MAP). Perform an OBDII scan for stored fault history to avoid buying parts you don't need. Do the cheapest fixes first. Go ahead and change the fuel filter also. There is a lot of water in todays fuels

I can be problem with IAC valve or motor,or there can be vacuum leak issue it its dirty Idle control valve or problem with dirt build up in throttle body.Click this link below and follow step by step troubleshooting:-----http://whatisbyme.blogspot.in/2012/05/high-idle-on-chevy-blazer.html
---------------this should help.Thanks.

IAC idler air control valve bumps up the RPM and doesnot let the engine to die, how ever if its not the IAC then Ide be looking at the TEMP sensor which migh have a fair line crack or may be the MAF mass air flow sensor might be bad, seems like the engine is not geting air, check the air filter first.

http://www.2carpros.com/questions/chevrolet-blazer-1995-chevy-blazer-trouble-code

turn ign on pump acc pedal 5 times start engine it should go out

Inspect/replace air filter.
Fill the gas tank to above 3/4 and add Lucas FUELSYSTEM CLEANER.
Ran on the highway for 10+ miles.

Monitor is the rough idle condition is getting worst on below 1/4 tank.
Change fuel filter and check fuel pressure.
Most failing/weak fuel pump will not work well below 1/4 tank mark.
It will fail in a HOT DAY.

Do you know if the plugs were changed, a bad or broken plug will also cause rough idle and slow acceleration?

check your Throttle Positioning sensor that should fix your rough idle the TPS controls the breather on the front of the engine its affixed to the right hand side of the throttle body just infront of the spyder on the V6 Vortec 4.3L Models