I put a new L98 in my 89 TA, and when I was messing with the timing I noticed that When I hit the throttle the timing retards about 10-12 degrees. I was wondering if that was normal. I figured that as the rpms went up the timing would advance. I put a new knock sensor on it and ot still does the same thing.

 

With the ECM connected, timing will be more advanced at idle/no-load than when you hit the throttle. Just like the "old days" with a vacuum/mechanical advance distributor, when vacuum goes down (like when you hit the throttle), advance goes down.

For the record: The timing is "set" with the ECM wire disconnected. That is the "base" timing. Anything you do with the timing light after that is for amusement purposes only.

 

I had the ecm disconnected

 

How certain of that are you?

With the ECM disconnected, the "limp home mode" will advance with RPMs only, from what I've seen & heard.

 

To set the static timing you disconnect the brown and white wire on the passenger side of the car over by the heaterbox. So that's what I did.

 

Okay, I'll let someone else chime in then. If it was retarding that much, then it would have been ATDC as you blipped the throttle.

 

This may be a dumb question and I'll probably feel pretty stupid when you answer it but what is the ATDC?

 

Stupid me after top dead center. Had a brain fart temporarily.

 

What RPM was it at and how high did you rev it?

 

I set the timing at about 900-1000 rpms, and I reved it to about 3500.

 

With the ECM disconnected, the engine won't even start or run.

Maybe you had just the EST disconnected?

I wouldn't waste time troubleshooting w/ EST open, just hook it up and run it w/ a scanner attached to verify correct operation.

 

2 questions
A: where do I get a scanner and
B: It will tell me if the timing is correct.