cjserio

Here's the situation....3VZE in diagnostic mode....engine sitting perfectly idling at 800rpm. I put a timing light on it and see a perfect 10 BTDC...It doesn't jump around, it sits there perfectly frozen,

If I give it some gas, the timing marks are no longer visible and it looks like it's jumping all over the place. I'm assuming this is normal or is that a bad assumption?

If it's normal, can someone explain to me why the timing moves that much that it wouldn't be visible with a timing light anymore? I would think that the computer would move the timing MAYBE +/- 10 degrees which should still be visible to me.

If it's not normal and I should see the timing slide, what could be wrong? The engine runs mostly well but I'm fighting a efficiency/performance/smog issue so it's not perfect.

Here's the timing light I'm using....
http://www.amazon.com/Actron-CP7527-.../dp/B000BSY9J4

xxxtreme22r

might be normal, art least on a 22r it is because the mechanical advance in the distributor, not sure if the 3vz has the mech adv though.

This reminds me I think I knocked my ign timing off got to check it today. lol.

vasinvictor

iTrader: (3)

Are you saying after you bump the throttle, and returns to idle, it won't stay stationary? Or while giving it gas, it disappears? Does the truck run out good, or what is the cause for complaint here?

cjserio

Once the truck idles again, the timing is just fine...it's while the RPM is up above idle that I can't see the timing marks.

As I said in my original post, I'm trying to track down a performance issue.

vasinvictor

iTrader: (3)

If the base timing is good, look elsewhere for you issues. Ecu take care of timing advance. Look at plug wires, cracks in air intake hoses, or bad tps to give you a start.

vasinvictor

iTrader: (3)

My BBC Chevy likes 38* total timing with a base of 8*, so that 30* of movement. I'm assuming most gasoline motors like similar timing. Be hard to see 30* of movement on crankshaft timing marks.

cjserio

Ah understood...ok thanks!

xxxtreme22r

With the jumper installed ECU does not control timing, that's the whole point in the jumper. Someone more familiar with the 3vz need to confirm if the distributor on those actually has mechanical advance on it or not.