1994 s10 Blazer CPI vin W. I wanted to adjust my timing so I found the wire underneath the carpet and unplugged it. Right away my truck started to surge and throw codes. It threw code #34 which is Vacuum sensor or MAP sensor, and code #42 which is Electronic Spark Timing (EST). My question is that should it be throwing any codes at all when that wire is disconnected?

 

Wire under the carpet? What kinda manual you getting your info from there?

 

On the first gen. blazers there is a brown wire located on passenger side, under the carpet near the fire wall that needs to be disconected to disable the timing advance. IIRC when the wire is disconnected it will throw a code but I do not remember what code it is, but it should not cause any Idle issues while you adjust the timing. The code will clear once you complete your timing and re-connect the wire. I have timed my vehical numerous times and never had idle issues with the wire disconnected. I would make sure that no vacuum lines got broke or disconnected. Did you plug the vacuum port for the air cleaner? It sounds like a vacuum leak to me.

 

Everywhere it's a 1st gen blazer, your truck is different. When i disconnect the timing wire (the wire under the carpet) the computer no longer controls it, it goes to the mechanical timing, with the wire plugged in the computer will advance the timing up to 10 degrees.

Everything is plugged in no vacuum leaks, im leading toward a bad MAP sensor, but will know after I adjust the timing.

 

That's the great thing about this forum, I learn something new everyday...

 

Just wait until you find out what else you can do with the old ones