Hello,

New to the site and needing help on my 1994 silverado 2500 4x4 350 with tbi set up.

I replaced the motor last year and only has 2000miles on rebuild.
it was running good up to couple weeks ago, I noticed at idle motor would surge between 500 to 1000 rpm and the service engine soon light comes on. If I drive down the highway truck performs well.
when I shut off and restart, sometimes light will go out and runs idles fine.

What I have replaced with motor, EGR, pcv,new distributor, plugs, wires, new intake gasket and manifold,

Cleaned TBI, Is there maybe a sensor that is acting up, any help greatly appreciated

 

Perhaps issues with the Idle Air Control (IAC) sensor or Throttle Position Sensor (TPS). Check their connections and give them a cleaning maybe, or try them with working models, if you don't want to go on a trial and error purchasing spree.

What you need to do is grab the code that the Engine Light is coming on for. That should provide some clues.

 

Is there a trick to get code? I have a scanner that reads 1996 and newer.

 

This should help: How to read older GM OBD diagnostic codes for free

Will blink the codes for you.

 

Thanks for info, will these codes show up on dash?

 

The check engine light will blink the sequence of the codes, so for example, a code 32 will blink three times, and then two more times to equal a code 32. I believe it will blink the same code like three times in a row, then move onto the next one.

 

NullHead is correct. Though the check engine light will first blink once then twice (and repeat this three times) for code 12, meaning the VCM passed a self-diagnostics test. A longer pause will be seen then the trouble codes will flash in the same manner: first number, pause, second number, repeated three times, then loop back to 12.

 

Thanks for replies, I will try that today and let you know results.