Where to find and unplug timing wire

[Chevy3+3]

I want to double check my timing and I was told there is a single wire I need to unplug before I adjust the timing. Problem is I don't know what color the wire is and where to locate it on my truck.

1988 Chevy 1 ton CC Dually 4x4.

Any help would be great. I'm just trying to wake the 454 up and I have heard they like around 4 to 8 degrees advanced

[bilfman]

Unplug the brown wire from dizzy , timing is set at 0 then.

[Desert1957]

Above mentioned "Brown" wire is on the firewall harness near the master cylinder. Here is my 87 R10.



There have been many threads on this topic...

Desert

[Chevy3+3]

I was told that the timing was most likely set at 0 when is left the factory but I thought the current recommendation said it needed to be set at 4 degrees and as long as you don't get any pinging the 454 really likes being set at around 8 degrees.

[Chevy3+3]

Okay thanks for the picture. I had seen that wire but I was told to be looking for a brown wire w/a black stripe. The wire in the pic is a brown w/ white stripe.

[Desert1957]

Originally Posted by Chevy3+3

Okay thanks for the picture. I had seen that wire but I was told to be looking for a brown wire w/a black stripe. The wire in the pic is a brown w/ white stripe.

1. Install Timing Light
2. Start Engine (warm up fully)
3. Check for Timing Mark (Might be way off scale)
4. Disconnect Wire Shown in Pic
5. If Timing Mark Appears Its The Correct Wire

Do not get too crazy with advancing the initial timing, If you do the "Knock Sensor" will just retard it anyway. 2-4 degrees is plenty.

Carb Big Blocks is a different story.

Desert

[Sodell]

Put it on Zero. Unhook the battery for a bit and then drive it. The ECM will adjust it.

[Chevy3+3]

What will unhooking the battery do? I actually want the timing advanced a little bit. I hope it might perk the truck up a bit. Just seems sluggish and everything else appears to be working correctly.

[Desert1957]

Originally Posted by Sodell

Put it on Zero. Unhook the battery for a bit and then drive it. The ECM will adjust it.

ESC WILL adjust the timing while running, BUT you still need to set the INITIAL timing as posted above. Trust Me.

Desert

[LONGHAIR]

Disconnecting the battery "resets" the computer, which makes it start clean, w/o old timing calculations. It goes back to the original advance curve from the PROM chip.
There isn't much that can be done "physically" because the computer controls it.
IIRC, the '87s were the last of the "removable" chip ECMs where you could replace them with a Hypertech (or other brand) performance chip.......BUT, since the one tons, Blazers, 'burbs kept the same body for a few years? Maybe they do too?
After that, there were other "work-arounds" for the later computers, so all is not lost.

You are better off to "work with" the computer than fighting against it.

[Sodell]

Yep, you are correct- it adjusts it from 0, and you need to set it with the wire unplugged after the engine is warm. On the TBI you need to reset the ECM-eprom after changing timing or replacing sensors. The eprom has all the parameters stored in it and unhooking the battery will basically erase all the old ones. You can also jump the A&b terminals at the scan port to erase the eprom....FYI the 88 still has the same setup as the 87

[Chevy3+3]

Okay. Thanks to all that responded. I have been a long time chevy owner but this is my first big block and only my 2nd TBI. I had a worn out 350 TBI that could run circles around this 454 (even pulling) and both trucks had the same gear ratio. I was told by a certified chevy mechanic to unplug the wire and to advance the timing a little and plug the wire back in. He said it perks the motor up a bit and in his experience has sometimes seen a 1-2 mpg gain after doing so.

I'm really just trying to make the truck a little more responsive and not feel so sluggish.