mdm6713

What is involved in controling the advance / retard of the timing on the vortec 350? Im running between 15-35 degrees retard on my timing when it should be a few degrees advanced or at least near 0...I know theres no adjustment at the dist. itself by turning it...but what goes into the decision the truck is making to adjust timing that slow?

Ive replaced crank position sensor and knock sensor along with 4 02 sensors, one sensor was not giving a consistent reading back, I replaced it again and still have the same "lazy" reading. I realize I may have a wiring problem here(260K on a 96 model)

Any direction or help is appreciated
Michael

mdm6713

any ideas guys? Im using a laptop based scan tool..thanks

tinbender59

ok: if the Knock sensor "hears" a knock, it doesn't care what it is, it thinks it is "preignition" so it retards the timing and cuts fuel back some, trying to control the knock. this is the problem I had with a very agressive cam "to much noise" and this is why you NEVER see a solid cam in a EFI motor. nowto test this, as I said in the other post! unplug the knock sensor before you do any thing else. run it and look at your timing, if it comes back up? You may have noisy rods or mains, or even piston slap. with those kind of miles any thing is possable.

mdm6713

Hey...i unplugged the knock before, seem to improve a bit so i put a new one on, it does run a little smoother, but the timing still off. Do you know what other sensors have a part in deciding timing?
thanks for your help again

tinbender59

fuel pressure was the guilty culprit on my Tuned Port conversion, pressure was low so it was lean causing her to ping????.

David Caffey

Did you find the problem?