Is My Timing To Far Advanced ?

golfballs · April 7, 2008

I used a scanner and noticed at idle the timing adv degree jumps from 20.0 to 25.0, is this correct ? Engine shakes alot and is hard to start when cold. 2000 gmc g2500 5.7 105k.

aldridgec · April 13, 2008

The timing advance seems a bit high. i've never paid attention to what the timing is at idel. However, it sounds like you need to start your diagnostics else where as something is probably causing the driveability issues as well as the timing to be advanced. I assume there are no codes or check engine light?

Look for vacuum leaks, improperly installed air intake pipe between the mass air sensor and throttle body. Also scan other sensor values to see if anything looks improper.

golfballs · April 14, 2008

The timing advance seems a bit high. i've never paid attention to what the timing is at idel. However, it sounds like you need to start your diagnostics else where as something is probably causing the driveability issues as well as the timing to be advanced. I assume there are no codes or check engine light?

Look for vacuum leaks, improperly installed air intake pipe between the mass air sensor and throttle body. Also scan other sensor values to see if anything looks improper.

Thanks for replying, i have 0171 and 0174 bank 1 lean and bank 2 lean.

aldridgec · April 14, 2008

If the banks are lean, then it isn't metering the air properly, or there is a common leak to both banks. While the intake gaskets are failure prone, not so much for driveability and air leaks. It is easy for the air intake pipe to get improperly installed on the top of the mainfold because it can't be seen from behind. Even on the pickups it's not always seated right. I would start there and make srue all the tubing after the mas air flow sensor is in properly.

The other possibility is that the fuel pump is weak, or the filter is really clogged. There should be a fuel pressure tap at the back of the motor where the lines come up to the intake. You can check the pressure there both KOEO, and KOER. IIRC, pressure on the vortec at idle should be around 60.