Reset computer after setting timing? (Page 1/1)
Modesto JUN 08, 12:57 AM
I finished my 3.4 swap late Friday and I'm taking it in tomorrow to have the timing set. Do I need to reset the computer afterward?
fierofool JUN 08, 07:42 AM
No. Disconnecting the power after setting timing might cause you to think that the job wasn't properly done. When the power is disconnected from the ECM, it must relearn all the sensor inputs. That requires driving the vehicle for a while at highway speeds. Until it relearns, it runs in default mode. Sometimes, not very well. With the ECM staying connected, it learns any variables in sensors as the changes take place.

Just be sure that your service department understands that the ignition must be OFF when inserting AND removing the jumper to the ALDL diagnostic port. Otherwise, it's possible to damage the ECM. The jumper goes between the two lower terminals, passenger side of the ALDL. Most manuals show the ALDL terminal rotated 180 degrees as it's mounted under the dash of most vehicles. The Fiero has it turned upside down.

[This message has been edited by fierofool (edited 06-08-2020).]

Dennis LaGrua JUN 08, 09:31 AM
Only GM PCM's (96-up) when position sensors are replaced or the unit is used in an engine swap do require a reset called a "case learn".

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fierosound JUN 08, 09:56 AM

quote
Originally posted by fierofool:

Just be sure that your service department understands that the ignition must be OFF when inserting AND removing the jumper to the ALDL diagnostic port. Otherwise, it's possible to damage the ECM. The jumper goes between the two lower terminals, passenger side of the ALDL. Most manuals show the ALDL terminal rotated 180 degrees as it's mounted under the dash of most vehicles. The Fiero has it turned upside down.




The jumper connects the A & B terminals.
As mentioned, the port is usually mounted with the "key" facing down.


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[This message has been edited by fierosound (edited 06-08-2020).]

Modesto JUN 08, 04:06 PM
Thanks for the info! Sadly they can't get to it till tomorrow. I plan on letting it sit till I drive it to have the timing set (the shop is only a couple miles away), but at the same time its killing me not to drive it after all this work! It starts, runs and idles fine but I would just hate for something to get damaged.
Patrick JUN 08, 04:39 PM
I wouldn't trust some disinterested party to do something so important, yet so simple.

A few years ago I bought a very nice used inductive timing light on eBay for $10 or less.

I've had a timing light going back to the early 70's, but it was the old fashioned type where the connection had to be in-line with the #1 spark plug wire. Inductive timing lights are very nice to have, so easy to use.

[This message has been edited by Patrick (edited 06-08-2020).]

Modesto JUN 08, 04:48 PM
Yeah I just realized my neighbor probably has one. For how time consuming it could possibly be I would probably be money (and confidence) ahead even if I have to buy one.

Edit: He did indeed have one, and it was pretty painless. The hardest part was finding a place to aim the light that allowed me to see the timing scale at the same time. I'm a little sad because it doesn't sound as cool now, but it definitely runs smoother and has more power.

[This message has been edited by Modesto (edited 06-08-2020).]

fierosound JUN 09, 08:03 PM

quote
Originally posted by Modesto:

Yeah I just realized my neighbor probably has one. For how time consuming it could possibly be I would probably be money (and confidence) ahead even if I have to buy one.

Edit: He did indeed have one, and it was pretty painless. The hardest part was finding a place to aim the light that allowed me to see the timing scale at the same time. I'm a little sad because it doesn't sound as cool now, but it definitely runs smoother and has more power.