a little story about timing

[ChevyGuy1022]

So I grabbed my uncle's timing gun and decided to see if my timing was the reason my idle was so shaky. I get the gun plugged in and immediately notice the problem. My motor (3.1) was advanced about 19*! Seeing that it should be closer to 5, I got to workin on the distributor bolt, the most annoying fudgin thing in the world.

Using a box end wrench, not enough room to move the bolt. Using a socket wrench, we couldn't even get it on the bolt because the distributor plate did not allow much of a clearance.

After about 2 hours of trying to figure out what size bolt it was (because we couldnt get one on it to see if it fit), I went to the christmas presents and grabbed the stubby wrenches I had purchased for my dad. Because the head angles, we were able to get a socket on the bolt and FINALLY loosen it enough to adjust the timing.

Dad was a little peeved I was holdin out on him, but hey... He got a Christmas present a month early, so he was happy.

We got the advance back to 5* and tested it out. :D S m o o t h e s t idle I've ever seen on this car. So this is where the story turns into a question. How did the motor advance itself that much? What can wear that'll effect the timing? I thought it was only the timing chain that could stretch a little, but even then it wouldn't give much more than a degree or two.

I'm sorry for sounding like a twelve year old, but I'm really happy I was able to fix this, and I want to learn why it got that bad to begin with. Thanks in advance.

[Jerriko's Garage]

First, a question. Did you unplug the EST wire before attempting to time the engine? Second, if the timing chain jumped a tooth, it could be off by 14 or so degrees.

[ChevyGuy1022]

we followed the directions in the Chilton's manual. If I can remember off the top of my head, we jumped the EMC channels A and B to ground before checking the timing. And forgive me for being simple, but what exactly is the EST wire? We could have unplugged it anyhow, but I'm not sure.

[Jerriko's Garage]

You jumped what? I have never heard of jumping any channels to time a car. Please elaborate.

The EST (electronic spark timing) wire is the wire you unplug to put the ECM at base timing. If you try and time the car while the EST is still plugged in, the reading from the timing light will not be accurate, by a lot.

[3.8 nate]

isnt the stock timing liek 10*, peole bumping it up to 12* for the older motors?

[Jerriko's Garage]

Originally posted by 3.8 nate:
isnt the stock timing liek 10*, peole bumping it up to 12* for the older motors?

[ChevyGuy1022]

Originally posted by 3.8 nate:
isnt the stock timing liek 10*, peole bumping it up to 12* for the older motors?

Im not sure exactly what it is, but we have it at about 5 or 6 right now and it idles smoother than ever. I have noticed a little lull between about 3k and 5k rpm, but I figure it's just the computer readjusting some values. I'm givin it a week and if it needs to be retimed to a more advanced setting then hey, at least we know how to do it now. If anyone can find out what the stock timing is on the 3.1, please let me know.

[ChevyGuy1022]

Originally posted by Jerriko's Garage:
You jumped what? I have never heard of jumping any channels to time a car. Please elaborate.

Step 5 in the Chilton's guide reads:
To set the base timing, the ECM EST must be bypassed. To do this, do the following-
For all fuel injected engines (except 5.0L
TPI engine) - ground diagnostic terminal (terminals A and B) in the ALDL diagnostic connector.

So we ran jumper wires from the A and B to a ground in the engine bay. Timing light worked fine. I suppose that's why we didn't unplug any EST wire, because we bypassed it.

[3.8 nate]

Ohhhhhh, CHiltons. THE holy book haynes says to disconect the EST wire if indicated by the emission sticker. I just checked the 85 2.8 sticker, and the 88 TPI 350 sticker, and they each say the same thing: disconect the EST wire.

Is the 3.1 different somehow???

[ChevyGuy1022]

Originally posted by 3.8 nate:
Is the 3.1 different somehow???

Nuts if I know. All I know is it worked.

[3.8 nate]

recheck your timing by disconnecting the EST connector.

make us true beleivers. ;)

[Jerriko's Garage]

Originally posted by 3.8 nate:
recheck your timing by disconnecting the EST connector.

make us true beleivers. ;)

Yes, what he said. It's a little brown w/ black stripe wire sticking out of your wire harness. Unplug the connector and away you go!!!

[ChevyGuy1022]

When I redo my timing (to somewhere around 12*) I will do just that and repost here the results. Thanks guys.

[ChevyGuy1022]

Ok, so timing's set to 12*. Idle's nice and it's got the pep back in it's step. EST plug disco'd and all works fine. Thanks for the input guys.