I have a 94 blazer and recently decided to go to the shore(hour and a half trip from my house) and after about 15-20 min of going over 50mph my service engine light came on. I just had a oil change a week ago, put gas treatment in my tank last fill and my antifreeze tank is full. I can drive for hours without this coming on but once i go above 40-50 it comes on after a bit. Anyone know what the problem could be? BTW after this came on car still ran fine, no smoking or rougher than usual idling.

 

Check for codes. The check engine light is telling you that the ECU has detected a fault and stored a code to point you in the right direction.

 

how exactly do i do that lol sorry

 

Take it by an Advance Auto (free) or a local mechanic. Tell them you need to have the truck scanned for trouble codes because the engine light is on. They'll plug it into a computer and get a (or some) code(s) such as PO140 or something of the type. That will tell you what the issue is. Beware that a shop will charge you a fee for doing this.

Or you could get the codes and post em up here.

 

Find a paper clip and follow the directions on TroubleCodes.net.

 

He's got an OBD I vehicle, which has numeric-only codes. Advance, etc, do not have OBD I readers, only OBD II.

The paperclip method mentioned by Kyle is free and it works perfectly.
http://www.troublecodes.net/GM/

 

Yep, it's pretty simple to get the codes outta an OBD1 but it's a pretty archaic system so don't go changing the oxygen sensor (or whatever) right off the bat. Try to figure out what's actually causing the device to set the code.

 

My fault I thought I read 98 instead of 94 for some reason.

 

Archaic? or user friendly on a system that doesn't have as much emission garbage?
OBD 1 can be checked with a paper clip OBD2 and avove require a trip to the auto parts store at the least.

 

did you ever figure out what was causing? i have the same problem. everytime i run the code check it says normal. can you check it while its running?