Uncle Phippy

I finally got my 1990 L98 Vert put back together and running. Doesn't run quite right, almost but not quite. It was suggested that I manually check the timing. My book says to disconnect the ECM harness at the distributer, but when I do that, it won't start. I hooked everything back up and I have 12 degrees BTC. What wire connector am I suppose to disconnect to get an accurate reading?

ch@0s

http://forums.corvetteforum.com/atta...ion-timing.doc

Uncle Phippy

Thanks for the quick response, but, believe it or not, I just replaced my computer and don't have Microsoft Office yet. So, I can't open the link you gave me. Wish I could, I really need that info.

ch@0s

Open source is free and works

http://download.cnet.com/OpenOffice-...-10895350.html

MrWillys

I don't agree it needs to be in drive!

ch@0s

How about we let him try it both ways and tell us how it does Mr.Willi.

Frizlefrak

SQUIRMIN VERMIN 84

Quick to reject what works for everyone else....

Cliff Harris

The requirement to be in Drive for automatic transmissions makes zero sense.

The key is that with the EST connector open the timing is controlled by the ignition module. I have never seen anything that tells us what advance curve is built into the ICM. The problem is that we don't know at what RPM the ICM starts adding advance. As long as the RPM is below that mysterious RPM the gear the trans is in makes no difference.

The requirement to disconnect the battery for 10 - 30 seconds is bogus. I MEASURED the voltage decay rate and it goes to zero in less than 1 second (last diagram on the page):

http://home.earthlink.net/~cliff_har...orms.html#U1-4

Also, this connector (if you have it) is MUCH easier to open to reset the ECM than disconnecting the battery (no tools required):

Muffin

Cliff do you know what years had the ECM disconnect?

WW7

On my 383 auto because of the cam, the idle is set to 820 rpms in gear and around 875-890 out of gear.. I had always set my timing with the car in neutral until I read a post on here saying it should be set while in gear.. I tried setting it with the car in gear, and as soon as my buddy pulled it into drive with the est wire disconnected the timing stayed right at 6 degrees BTDC .. Never moved..Maybe it's because my car has a higher idle then stock , but on my 89 it doesn't make any difference which way I set it.. ...WW

ch@0s

My car idled better at stop lights when adjusted in drive. Maybe it was in my head?

Uncle Phippy

My 90 vert is a six speed. With the car in neutral, the EST disconnected, it was dead on 6 degrees BTC. Next step is to get a scanner and try to figure it out. Thanks for the help.

MrWillys

You can buy this cable:
https://www.moates.net/aldu1-and-cabl1-p-127.html

Download the software here:
http://www.ttspowersystems.com/DataM...ownloads2.html
Use it for 20 datalogs for free.

Step by step instructions on how to use it:
http://www.scotthansen.net/data.html

My guess would be lean stumble, or hesitation as I've already said if you installed the Bosch yellow 280-155-700. The only solution (still not perfect) is to change the flowrate in the programming to 20 lb injectors.

Cliff Harris

I don't. My '86 has it but I have heard that some years do not. That's why I was intentionally vague. I just don't know.

Muffin

My 85 has it, mentioned it here once got flamed big time for "Redneck add on's". Sure makes clearing codes a snap.

Uncle Phippy

Does it clear the "SES" on the DIC? Disconnecting the EST to manually set the timing seems to have set the SES.

MrWillys

Disconnecting the ESC bypass does set a code 42. Disconnect the negative cable, or Cliff's little secret disconnect to clear code set when checking, or setting timing after ESC wire has been reconnected.

JackDidley

If you drive the car after a restarts the SES will go out anyway. Saves resetting the radio and clock.

MrWillys

Jack,
Disconnecting the ESC bypass sets an SES light. Once it is plugged back in the SES light goes out, but the stored 42 code stays until removed by clearing with a scanner, or resetting the ECM by removing power for a short time.