I just replaced my timing chain today. Once I was done I decided to check the timing. It was way off. Then I remembered that the timing wire needs to be disconnected to check the timing. I disconnected the timing wire and the timing was at about 12º. Not too far from the 10º it's supposed to be at.

It's not a big deal to readjust the timing, but then I got to thinking. If the computer can adjust the timing, does it really matter if my uncontrolled timing is off by two degrees? I figure there must be a limit to how much the computer can compensate.

Maybe I'm misunderstanding the way the timing adjustments work. Can some explain what the ECU does to adjust your timing and how it is affected by "fixed" timing setpoint?

1992 3.1L V6

Thanks

 

Yes i would like to know that as well.

And how do you actually adjust the timing on these things...

 

The ECM can only adjust timing up from the base setting. During different RPM, load, and throttle positions. Say that under a certain load the computer calclates that you need 10 degrees of extra timing, if the base timing is at 10, then your adjusted timing is 20, if you have base set at 12, then it's 22. The computer ONLY assumes that the distributor is at 10* base timing. It has no way of telling if it's actually adjusted higher or lower.

If you have a 3.1L with a knock sensor, then it can adjust down from the computer adjusted timing, but still cannot go lower than whatever you set it at.

Generally speaking, the computer adjusts timing based on the assumption that you have set it at 10* BTDC, that's it. If you move it, you affect the computed timing by the same amount.

 

Thanks for the response. My understanding is that the computer controlled part is just an offset based on varying engine conditions. Probably a look up table or something.

There is one bolt that holds down the distributor shaft in place. When you loosen the bolt, it allows you to rotate the distributor. This adjusts your timing.

You need to make sure to disconnect the timing wire that the computer uses to adjust the timing. It is a connector with tan wires sticking out of a wire bundle near the passenger rear of the engine bay.

You make small adjustments to distributor position, then using a timing light check the timing, adjustment, check timing...

 

That is what people keep telling me, but my dist. CANNOT twist.

Don't get me wrong, i appreciate you taking the time to tell me. but its driving me crazy. If i can't adjust the dist. how am i supposed to change anything? lmao And i know i need to.. its way off.

 

Your trying to rotate the dizzy with the engine running right?
If I remember correctly, that bolt is the only thing holding the distributor in place. If you completely remove the bolt, you can pull the whole assembly out. Maybe it's just stuck and requires some persuasion.