I have been reading posts on this site and let me just say thanks cause everybody has already helped out a bunch. I installed a map tuned port on my 89 S10 350. Built my own harness from an 87 tpi harness. All in and started and idled good. Does not advance timing after starting or when trying to rev it. Tried 3 seperate distributors which were known good. Checked and double checked my wiring for distributor. 3 different computers. No luck. Then it started working one day. Drove it a couple days and back to where I started. I burned my own chip but I only unchecked the VATS to make it run. Tried a second eprom to be sure it wasn't that. Same story. I have been messing around with this for 3 weeks and have yet to figure anything out. From what I read the white wire going to the distributer controls advance. It seems to do what its suposed to with aprox. 1.3 volts at idle from the computer. I really need help on this. It has been driving me crazy. Thanks in advance.

 

check for a code 43 Knock Sensor Circuit
if you have this you will not get any timing advance.
make sure the knock sensor wire (usually blue) isnt grounded on
a header, ohm the knock sensor wire to computer and then to ground
to make sure of continuity and non grounded.
measure the resistance of the KS. from the pin to ground should be
39k (39000) ohm. i usually measure at the body of the KS.
next measure the voltage on the KS wire. key on and engine off.
voltage should be between 2.5-4.5volts.
make sure you have the "1348" eprom. the knock modules are
different and could be a voltage error.
scan and detect if the computer detects a knock.
airdeano

 

I will check KS as you said. I know for a fact there are no codes coming up though. I tried a different knock sensor yesterday with no luck. I did check continuity of the wire but can't remember if I checked to see if it was grounded. Pretty sure its not though. Check for sure tomarrow. The original sticker of my new eprom has "1348" on bottom and I am assuming that is what you are refering to about the knock module. I don't have a scan tool but I will talk to someone about using one. Basically I could get away with grounding the blue wire though a 63k resistor to bypass the knock sensor to eliminate that as a problem correct? Thank for the help

 

Well I must say you called that one right. Ended up putting in a new knock sensor now its advancing. Thanks alot.